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ARMY NAVY DRIVE

MARCH | 2017TRAFFIC STUDY

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Traffic Study

Army Navy Drive Traffic Study

Arlington County, VA

Prepared For: Arlington County, Division of Transportation 2100 Clarendon Boulevard, Suite 900 Arlington, VA 22201 (703) 228-3681

Prepared By: Kittelson & Associates, Inc. 1850 Centennial Drive, Suite 130 Reston, Virginia 20191 (703) 885-8970

Project Manager: Brandon Nevers, Pr. Eng., P.E. Lead Analyst: Jon Crisafi, P.E.

Project No. 11834.32

March 2017 Updated: June 2017

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TABLE OF CONTENTS

Executive Summary ................................................................................................................................ 1

Operations Findings ..................................................................................................................................................................... 1

Scenario Findings ......................................................................................................................................................................... 4

Geometric Recommendations ..................................................................................................................................................... 5

Signal-Related Recommendations ............................................................................................................................................. 12

Introduction ..................................................................................................................................... 15

Study Area ................................................................................................................................................................................. 15

Scope of Project......................................................................................................................................................................... 15

Existing Conditions ............................................................................................................................... 21

Transportation Facilities ............................................................................................................................................................ 21

Transit Facilities ......................................................................................................................................................................... 22

Existing Conditions Traffic Analysis ........................................................................................................................................... 22

Existing Conditions Findings ...................................................................................................................................................... 26

Travel Demand Modeling ..................................................................................................................... 29

Network Modifications – 2015 Model ....................................................................................................................................... 29

Study Area Conditions – 2020 Model ........................................................................................................................................ 32

Study Area Conditions – 2040 Model ........................................................................................................................................ 32

Design Concept Refinement ................................................................................................................ 35

Initial Design Concept ................................................................................................................................................................ 35

Initial Observations.................................................................................................................................................................... 35

Bicycle Treatments .................................................................................................................................................................... 37

Transit Treatments .................................................................................................................................................................... 37

Qualitative Evaluation ............................................................................................................................................................... 45

Concept Refinement .................................................................................................................................................................. 46

Future Conditions Analysis................................................................................................................... 49

Background Developments ....................................................................................................................................................... 49

Year 2020 and 2040 No-Build .................................................................................................................................................... 50

Year 2020 and 2040 Build .......................................................................................................................................................... 59

Comparison Across All Scenarios ............................................................................................................................................... 68

Summary of Findings ............................................................................................................................ 81

Scenario Findings ....................................................................................................................................................................... 84

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Recommendations ............................................................................................................................... 87

Geometric Recommendations ................................................................................................................................................... 87

Signal-Related Recommendations ............................................................................................................................................. 93

References ..................................................................................................................................... 96

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LIST OF FIGURES

Figure 1 – S Joyce Street/Army Navy Drive Recommendations Summary ............................................ 6

Figure 2 – Pentagon Mall Garage/Army Navy Drive Recommendations Summary .............................. 7

Figure 3 – S Hayes Street/Army Navy Drive Recommendations Summary ........................................... 8

Figure 4 – S Fern Street/Army Navy Drive Recommendations Summary ............................................. 9

Figure 5 – S Eads Street/Army Navy Drive Recommendations Summary ........................................... 10

Figure 6 – Army Navy Drive/12th Street S Recommendations Summary ........................................... 11

Figure 7 – Existing Lane Configurations and Traffic Control Devices ................................................... 16

Figure 8 – Existing Traffic Operations – Weekday AM Peak Hour ....................................................... 24

Figure 9 – Existing Traffic Operations – Weekday PM Peak Hour ....................................................... 25

Figure 10 – Modified Network in Army Navy Drive Study Area .......................................................... 30

Figure 11 – Original Network in Army Navy Drive Study Area ............................................................ 31

Figure 12 – Initial Design Concept Considerations .............................................................................. 36

Figure 13 – S Joyce Street Median Transit-Lanes Concept Movements .............................................. 39

Figure 14 – Parking Garage Driveway Median-Transit-Lanes Concept Movements ........................... 40

Figure 15 – S Hayes Street Median-Transit-Lanes Concept Movements ............................................ 40

Figure 16 – S Joyce Street Outside-Transit-Lanes Concept Movements ............................................. 42

Figure 17 – Parking Garage Driveway Outside-Transit-Lanes Concept Movements ........................... 43

Figure 18 – S Hayes Street Outside-Transit-Lanes Concept Movements ............................................ 43

Figure 19 – Joyce Street AM (left) and PM (right) Ring-and-Barrier .................................................... 44

Figure 20 – Joyce Street AM (left) and PM (right) Ring-and-Barrier .................................................... 44

Figure 21 – Hayes Street AM (left) and PM (right) Ring-and-Barrier ................................................... 45

Figure 22 – Location of Background Developments ............................................................................ 49

Figure 23 – No-Build Lane Configuration and Traffic Control Devices ................................................ 51

Figure 24 – Year 2020 No-Build Traffic Operations – Weekday AM Peak Hour .................................. 52

Figure 25 – Year 2020 No-Build Traffic Operations – Weekday PM Peak Hour .................................. 53

Figure 26 – Year 2040 No-Build Traffic Operations – Weekday AM Peak Hour .................................. 54

Figure 27 – Year 2040 No-Build Traffic Operations – Weekday PM Peak Hour .................................. 55

Figure 28 – Build Lane Configuration and Traffic Control Devices ...................................................... 63

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Figure 29 – Year 2020 Build Traffic Operations – Weekday AM Peak Hour ........................................ 64

Figure 30 – Year 2020 Build Traffic Operations – Weekday PM Peak Hour ........................................ 65

Figure 31 – Year 2040 Build Traffic Operations – Weekday AM Peak Hour ........................................ 66

Figure 32 – Year 2040 Build Traffic Operations – Weekday PM Peak Hour ........................................ 67

Figure 33 – Average Network Delay for All Vehicles by Scenario ........................................................ 69

Figure 34 – Average Network Delay for Passenger Cars by Scenario .................................................. 69

Figure 35 – Average Network Delay for Transit by Scenario ............................................................... 70

Figure 39 - Summary of Transit Travel Time Increases at S Hayes St/Army Navy Dr .......................... 71

Figure 40 – Spot Speeds during AM Peak Hour ................................................................................... 73

Figure 41 – Spot Speeds during PM Peak Hour ................................................................................... 73

Figure 42 – Intersection Delay during AM Peak Hour ......................................................................... 75

Figure 43 – Intersection Delay during PM Peak Hour .......................................................................... 75

Figure 44 – Measured Southbound Queue Storage at S Hayes Street/Army Navy Drive ................... 76

Figure 45 – S Joyce Street/Army Navy Drive Recommendations Summary ........................................ 87

Figure 46 – Pentagon Mall Garage/Army Navy Drive Recommendations Summary .......................... 88

Figure 47 – S Hayes Street/Army Navy Drive Recommendations Summary ....................................... 89

Figure 48 – S Fern Street/Army Navy Drive Recommendations Summary ......................................... 90

Figure 49 – S Eads Street/Army Navy Drive Recommendations Summary ......................................... 91

Figure 50 – Army Navy Drive/12th Street S Recommendations Summary ......................................... 92

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LIST OF TABLES

Table 1 Intersections with Peak Hour LOS E or Worse by Scenario....................................................... 2

Table 2 Army Navy Drive Traffic Study Intersections .......................................................................... 15

Table 3 Summary of Roadways within Study Area .............................................................................. 21

Table 4 Existing Peak Hour Conditions - Intersection Delay and LOS .................................................. 23

Table 5 Two-way Volume Comparison for Army Navy Drive ............................................................... 31

Table 6 Lane-Configuration Revisions for Median-Transit-Lanes Concept .......................................... 38

Table 7 Estimated Cycle-Length Increase or Decrease (in Seconds Compared to Existing Conditions)

Required to Accommodate Demand with Median Transit Lanes ........................................................ 39

Table 8 Lane-Configuration Revisions for Median-Transit-Lanes Concept .......................................... 41

Table 9 Estimated Cycle-Length Increase or Decrease (in Seconds Compared to Existing Conditions)

Required to Accommodate Demand with Outside Transit Lanes ....................................................... 42

Table 10 Evaluation of Median and Outside Transit Lanes ................................................................. 46

Table 11 Transit Travel Times .............................................................................................................. 71

Table 12 Intersection Performances during AM Peak Hour ................................................................ 74

Table 13 Intersection Performances during PM Peak Hour ................................................................ 74

Table 14 Maximum simulated Queues at Southbound Hayes Street/Army Navy Drive Intersection 76

Table 15 Maximum simulated Queues at Eastbound Eads Street/Army Navy Drive Intersection ..... 77

Table 16 Intersections with Peak Hour LOS E or Worse by Scenario .................................................. 82

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APPENDICES

Appendix A - Calibration Summary Memorandum

Appendix B – VISSIM Existing Traffic Operations Results

Appendix C – TDM Network Modifications

Appendix D – TDM Model Volume Plots

Appendix E – Existing and Future TDM Volumes and Field Measurements

Appendix F – Transit Lane Concept Analysis

Appendix G – Background Development Site Plans

Appendix H – VISSIM Future Traffic Operations Results

Appendix I – Signal Timing Parameters

SECTION 1

Executive Summary

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1

EXECUTIVE SUMMARY

Arlington County has begun an effort to modify the existing Army Navy Drive corridor in Pentagon City

to better accommodate transit users, pedestrians, and cyclists. In support of this effort, a detailed

traffic operations analysis was performed for the Design Concept developed by the County, which

includes a two-way protected bike lane, median transit way, and enhanced pedestrian crossings. This

concept was evaluated through microsimulation modeling. Existing conditions models were developed

and calibrated for weekday a.m. and p.m. peak periods. These models were then used to develop

future scenarios for Year 2020 (opening year) and Year 2040 (design year) for both the no-build

condition (background development only) and the build condition (background development and

implementation of the Design Concept).

The Design Concept evolved through a series of multimodal operational analyses and discussions with

Arlington County staff. This resulted in modifications to lane configurations at certain intersection

approaches, additional and reconfigured bicycle facilities, and relocated transit lanes from the median

to curbside.

This report summarizes the iterative design and analysis process used to evaluate and modify the

Design Concept along with the overall findings and recommendations for advancing the project forward

to the next stage of the design process.

The following sections highlight the key findings from the operational analyses conducted for existing,

future no-build, and future build conditions.

OPERATIONS FINDINGS

While the purpose of the Design Concept is to promote and accommodate active transportation

(pedestrians and bicyclists) and transit use along Army Navy Drive, this study focuses on the automobile

and transit performance associated with the proposed improvements. Given the right-of-way

constraints along the Army Navy Drive corridor, trade-offs are inherent when accommodating multi-

modal needs. For corridors that undergo complete street improvements to provide pedestrian, bicycle,

and transit facilities, oftentimes traffic operations for vehicles degrade due to the reduction of travel

lanes and intersection capacity. The purpose of this study is to identify the level of impact to traffic

operations along the corridor and identify mitigation strategies to reduce impacts while

accommodating safety and the performance needs of non-auto users.

The operational analysis of existing, future no-build, and build traffic conditions identified several

intersections and movements that experience long queues, traffic congestion, and turning movements

that operate at Level of Service (LOS) E or F, which causes motorists at those movements to experience

high delays. Table 1 summarizes which intersections are anticipated to experience this by scenario.

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Table 1 Intersections with Peak Hour LOS E or Worse by Scenario

Peak Hour Intersection 2015 Existing 2020 No-Build 2020 Build 2040 No-Build 2040 Build

AM

Army Navy Drive & Joyce

Army Navy & Pentagon Mall E E

Army Navy & Hayes E E F

Army Navy & Fern

Army Navy & Eads E E E

Army Navy & 12th* F* F E E F

PM


Army Navy & Pentagon Mall

Army Navy & Hayes E

Army Navy & Fern E E

Army Navy & Eads F F F F

Army Navy & 12th* * F F F F

*Indicates unsignalized intersection configuration

While individual intersection operations do not reflect the complete picture of how the system

performs under different Design Concepts, it helps identify the location of bottlenecks and “hot spots”

to warrant more-detailed investigation.

S Joyce Street/Army Navy Drive

Positioned on the western end of the corridor, the intersection at S Joyce Street/Army Navy Drive is

anticipated to operate at LOS D or better under all scenarios. Notable findings include:

The eastbound approach experiences higher delays under the build scenarios notably due to

heavy left-turn movements limited by protected-only phasing.

The 2040 build scenario is exacerbated by heavier volume demands on all approaches,

particularly left-turns.

Pentagon Mall Garage/Army Navy Drive

The intersection at Pentagon Mall Garage/Army Navy drive is expected to experience LOS E or worse

under both 2040 no-build and build scenarios during the weekday a.m. peak hour. Notable findings

include:

The westbound left-turn movement into the parking garage experiences the highest delay of all

movements at the intersection in all scenarios.

Reconfiguration of the parking garage exit in the build scenario is anticipated to accommodate

traffic demands without undue delay and queuing.

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S Hayes Street/Army Navy Drive

The intersection of S Hayes Street/Army Navy Drive is among the most critical along the corridor. It is

projected to operate at LOS E, or worse, under both build scenarios and 2040 no-build conditions

during the weekday a.m. peak hour. In all scenarios, the intersection’s connection to Interstate-395 (I-

395) and Washington Boulevard required queuing to be managed on the southbound approach to

prevent spillback onto the freeways. Notable findings include:

Northbound left turns experience high delays under both build and no-build conditions.

Southbound lefts experience high delays attributed to high demand.

Dual southbound left turn lanes were analyzed but have limited benefit due to queuing on the

downstream approach.

Results from the Vissim simulation analysis indicate that the maximum queue on the

southbound approach is not anticipated to spillback onto either I-395 or Washington Boulevard

under any future scenario analyzed.

S Fern Street/Army Navy Drive

The S Fern Street/Army Navy Drive intersection is mostly a point between the bottlenecks at S Hayes

Street and S Eads Street. The intersection is anticipated to operate at LOS E, or worse, only during the

2040 scenarios, mostly driven by queue spillback and heavy side street demands. Notable findings

include:

The northbound approach is anticipated to experience high delays in all future scenarios.

Eastbound delays at the intersection are mostly due to queue spillback from the S Eads

Street/Army Navy Drive intersection.

S Eads Street/Army Navy Drive

The intersection at S Eads Street/Army Navy Drive is a bottleneck along the corridor, given it is used to

access northbound I-395 and bus routes destined to the Pentagon. Both no-build and build lane

configurations have notable limitations in facilitating the traffic demand in future scenarios. Notable

findings include:

Eastbound left-turn queues consistently spill back through S Fern Street and S Hayes Street,

limiting throughput of the western intersections.

The heavy eastbound left-turn movement demand conflicts with a heavy westbound through

movement demand, thus competing for green time and causing delays to automobiles and

buses.

Northbound S Eads Street is constrained by a single approach lane given the relatively short

turn pockets.

The I-395 HOT lanes and associated improvements are expected to improve the operations at S

Eads Street and may relieve some of the anticipated congestion.

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Army Navy Drive/12th Street S

The intersection is currently unsignalized. Based on Arlington County plans, the intersection is planned

to be signalized in conjunction with the neighboring Clark Street/12th Street S intersection in the future.

The signalization will include the addition of median-running transit lanes as part of the 12th Street S

transit facility project. These improvements were assumed in the all future build and no-build

conditions. Notable findings from the analysis of this intersection include:

If unsignalized, the southbound movements are projected to experience significant queuing and

delay.

If signalized based on current plans, the following operational inefficiencies are anticipated: o Long clearance intervals due to the separation of the two intersections (12th Street and

Clark Street); o Limited flexibility to reallocate green time across phases due to the two-intersection

phasing. o The intersection (in conjunction with 12th Street S/Clark Street) has heavy turning

volumes compared to through volumes.

SCENARIO FINDINGS

Existing Conditions

General findings from the simulation analysis of existing conditions include:

Simulation results match with field observations of queues and driver behavior.

Simulation results at the intersection level are comparable to the Synchro analysis results.

Future No-Build Conditions Findings

General findings from the simulation analysis of no-build conditions include:

Significant congestion was observed in both future years during the weekday a.m. and p.m.

peak hours, notably at S Hayes Street, S Fern Street, S Eads Street and 12th Street

intersections.

Queue storage on the southbound S Hayes Street approach (I-395 ramp) is accommodated

through 2040 for both a.m. and p.m. peak hours.

The observed bottleneck is the eastbound approach at S Eads Street/Army Navy Drive. The

current eastbound lane configuration consists of a left-through and through-right layout,

which negatively impacts the progression of left-turn and through movements. The future-

year simulation analysis shows that demand is heavy on all legs with the predominant

conflicting movements being the eastbound left-turn movement and westbound through

movement. With heavy volumes destined to northbound I-395 and the limitation of a single

receiving lane, congestion is not expected to be alleviated by signal timing and phasing

improvements.

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Future Build Conditions Findings

General findings from the simulation analysis of build conditions include:

Significant congestion was observed in both future years during both weekday a.m. and

p.m. peak hours, notably at S Hayes Street, S Fern Street, S Eads Street, and 12th Street S

intersections.

Queue storage on the southbound S Hayes Street approach (I-395 ramp) accommodates the

back of queue through 2040 for both weekday a.m. and p.m. peak hours.

Both build and no-build conditions show a major network bottleneck at the S Eads


o Similar to the no-build analysis the future-year simulation analysis indicates heavy

demand on all legs; the main conflicting movements are the eastbound left-turn

movement and westbound through movement. With heavy volumes destined to the

northbound direction towards I-395 and the limitation of a single receiving lane,

congestion is not expected to be alleviated by signal timing and phasing improvements.

o Queue storage for the eastbound left-turn is recommended to be extended as far as

possible, but block spacing remains a limiting factor. Even with maximum storage, left-

turn queue spillback is anticipated.

The overall Design Concept reduces vehicular capacity along Army Navy Drive by

reallocating right-of-way to non-auto users. However, as summarized in Table 1, all study

intersections anticipated to operate at LOS E, or worse, in 2040 will do so under both build

and no-build conditions, with the only exception being the intersection of Army Navy

Drive/S Hayes Street.

GEOMETRIC RECOMMENDATIONS

The following section summarizes the geometric recommendations, shown graphically in Figures 1

through 6.

6

1. Joyce Street/Army Navy Drive

a. Northbound approach should be designed with a bike box configuration to

accommodate WB cyclists exiting the bicycle facility and continuing WB on Army Navy

Drive or turning right onto Joyce Street.

b. Westbound approach should be able to accommodate U-turns to provide access to the

Harris Teeter parking garage due to closing the existing median left-turn lane.

c. Southbound approach requires maintaining a left-turn lane with minimum storage

consistent with existing configuration.

Figure 1 – S Joyce Street/Army Navy Drive Recommendations Summary

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2. Parking Garage/Army Navy Drive

a. The northbound approach should be modified to a dedicated left-turn, dedicated

through, and dedicated right-turn lane configuration.

b. Pentagon Transit Center Considerations - Resolution with the ultimate design of the

Transit Center by the Pentagon must consider the west crosswalk as the latest designs

currently do not depict this pedestrian crossing. Include revised southbound approach

to shared left/through lane and dedicated right-turn lane.

c. The westbound left-turn lane requires additional storage.

i. The current left-turn lane length shown in the Design Concept between Parking

Garage (on westbound Army Navy Drive) and Hayes Street (on eastbound Army

Navy Drive) should accommodate anticipated queues.

ii. Storage length of the westbound left-turn lane is as follows:

1. WB Army Navy Drive @ Parking Garage = 130-ft; 75-ft taper

Figure 2 – Pentagon Mall Garage/Army Navy Drive Recommendations Summary

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3. Hayes Street/Army Navy Drive

a. The near-side bus stop along eastbound Army Navy Drive requires pedestrian

accommodations across the two-way bike lanes; consider similar treatment to mid-

block stop between Joyce Street and Parking Garage.

b. The northbound bike lane should be aligned along the curb rather than between the

through and right-turn lanes to prevent right-turning cyclists from conflicting with right-

turning vehicles. The model assumed that northbound left-turning cyclists would merge

into the vehicle lanes, but there are alternatives for accommodating left-turning cyclists.

A two-stage left-turn bike box could be installed or a bike signal/phase could be

considered. Although, an exclusive bike phase would result in a longer cycle length.

c. The southbound right-turn lane should have advanced signage of pedestrian crossing for

the channelized lane to encourage motorists to reduce speeds.

d. Dual southbound left-turn lanes have been considered but are not recommended. The

eastbound downstream through capacity limits any benefit of dual left-turn lanes.

e. Storage length of the left-turns lane are as follows:

i. EB Army Navy Drive @ Hayes Street = 220-ft; 60-ft taper

ii. WB Army Navy Drive @ Hayes Street = 125-ft; 60-ft taper

Figure 3 – S Hayes Street/Army Navy Drive Recommendations Summary

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4. Fern Street/Army Navy Drive

a. Consider access management alternatives, such as limiting ingress at the driveway on

the far-side of eastbound Army Navy Drive at Fern Street and potential to implement

right-out only configuration to reduce conflicts with pedestrians and cyclists.

b. The northbound approach should be reconfigured as a designated left-turn lane,

through lane, and designated right-turn lane.

c. Storage length of the left-turns lane are as follows:

i. EB Army Navy Drive @ Fern Street = 150-ft; 60-ft taper

ii. WB Army Navy Drive @ Fern Street = 50-ft; 60-ft taper

Figure 4 – S Fern Street/Army Navy Drive Recommendations Summary

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5. Eads Street/Army Navy Drive

a. The eastbound left-turn lane requires the maximum storage possible within the block

due to heavy bus movements and traffic demands.

b. Consider revisions to the westbound approach to reduce conflict points; the design

should consider:

i. Restricting westbound traffic movements from US 110 (Jefferson Davis Highway)

from turning left onto Eads Street.

ii. Providing better accommodations at the existing pedestrian crossing on the US-

110 off-ramp. The County will conduct a marked crosswalk study in order to

determine what treatments are warranted for this location. The study will be

submitted to VDOT in a separate memorandum.

c. The northbound approach would benefit from elongating the two-lane cross-section

south to 11th Street S for additional capacity.

d. Storage length of the left-turns lane are as follows:

i. EB Army Navy Drive @ Eads Street = 420-ft; 60-ft taper

ii. WB Army Navy Drive @ Eads Street = 135-ft; 60-ft taper

Figure 5 – S Eads Street/Army Navy Drive Recommendations Summary

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6. Army Navy Drive /12th Street S

a. Transit-only lanes between Army Navy Drive and 12th Street S should be converted to

general traffic lanes to improve traffic throughput.

i. Transit-only lanes between both intersections do not reduce bus delay with

recommended signal timing/phasing, which allows buses to use the segment

exclusively.

b. Prohibit westbound left turns due to sight distance concerns. Must provide westbound

U-turn movement at S Eads Street/12th Street S intersection to access garage.

Figure 6 – Army Navy Drive/12th Street S Recommendations Summary

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SIGNAL-RELATED RECOMMENDATIONS

A 130-second cycle length is recommended for 2020 weekday a.m. peak hour build scenario.

A 140-second cycle length is recommended for 2020 weekday a.m. peak hour and both 2040

weekday a.m. and p.m. peak hour scenarios.

Implement protected-only left-turn phasing along Army Navy Drive to reduce conflicts between

westbound left-turning vehicles, pedestrians, and bicyclists.

Eastbound/westbound bicycle movements along the bike facility will run concurrently with the

eastbound through phase.

Ensure all pedestrian intervals meet MUTCD recommended standards.

The Army Navy Drive/12th Street S intersection meets traffic signal warrants under Year 2020

and Year 2040 volume conditions and should be signalized. It is recommended that this

intersection run on the same controller as Clark Street/12th Street S and will be constructed as

part of the Crystal City Potomac Yard (CCPY) Transitway Extension project.

All analyzed signal timing parameters found in Appendix I.

SECTION 2

Introduction

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INTRODUCTION

The purpose of the Army Navy Drive Traffic Study is to evaluate and provide recommendations for

Arlington County’s proposed Design Concept for Army Navy Drive between Joyce Street and 12th Street,

which is intended to better accommodate transit users, pedestrians, and cyclists. This study analyzes

the operational effects of the reconfigured corridor to identify fatal flaws and areas of potential

improvement as the project progresses toward final design.

STUDY AREA

The study area comprises the northern section of Pentagon City, which is a commercial area due south

of The Pentagon. The area is roughly bounded to the north and west by I-395, to the east by US 1, and

to the south by 15th Street South. Army Navy Drive is the northern most commercial arterial that has

direct access to I-395 and indirect access to US 1. Table 2 details the intersections that are included in

the study analysis.

Table 2 Army Navy Drive Traffic Study Intersections

No. Intersection Control

1 S Joyce St/Army Navy Drive Signalized

2 Mall Driveway/Army Navy Drive Signalized

3 S Hayes St/Army Navy Drive Signalized

4 S Fern St/Army Navy Drive Signalized

5 S Eads St/Army Navy Drive Signalized

6 Army Navy Drive/12th St S Unsignalized

7 S Joyce St @ Bonefish Driveway Signalized

8 S Hayes St/12th St S Signalized

9 S Fern St/12th St S Signalized

10 S Eads St/12th St S Signalized

Figure 7 shows a map of the study area and details the existing lane configurations of the study

intersections.

SCOPE OF PROJECT

The evaluation of the study area has been broken down into the following components:

Evaluation of existing conditions

Travel demand modeling for future traffic volumes

Design Concept evaluation

Evaluation of future conditions

These components are further detailed in subsequent sections of the report.

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Analysis Periods

Traffic data were examined to identify which peak hours to analyze in order to provide the most insight

to operational constraints of the roadway network. After reviewing weekend and weekday traffic data,

it was determined that the weekday a.m. and p.m. peak periods were the heaviest traveled.

Future analysis years were determined to remain consistent with the regional travel demand model:

Year 2015 – Existing conditions

Year 2020 – Opening year conditions

Year 2040 – Design year conditions

As a result of these analysis periods, a total of ten (10) scenarios were modeled for the traffic study in

five groupings:

1. 2015 Existing Conditions (AM and PM)

2. 2020 No-build Conditions (AM and PM)

3. 2040 No-build Conditions (AM and PM)

4. 2020 Build Conditions (AM and PM)

5. 2040 Build Conditions (AM and PM)

SECTION 3

Existing Conditions

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EXISTING CONDITIONS

The Army Navy Drive corridor is a commercial roadway in Arlington County, Virginia, just south of The

Pentagon’s campus. The area is bounded to the north and west by I-395, to the east by US 1, and to the

south by 15th Street South.

TRANSPORTATION FACILITIES

The study area roadway network is comprised of major collectors and minor arterials. The summary of

these facilities is found in Table 3.

Table 3 Summary of Roadways within Study Area

Roadway Functional

Classification1 Orientation Number of Lanes

Posted Speed (mph)2 Sidewalks

Bicycle Lanes

On-Street Parking

Army Navy Drive Major Collector East-West 6 35 Yes No Yes4

Joyce Street Minor Arterial North-South 4 25/353 Yes Yes Yes

Hayes Street Minor Arterial North-South 6 30 Yes Yes Yes

Fern Street Major Collector North-South 2 30 Yes No Yes

Eads Street Major Collector North-South 2 30 Yes Yes Yes

12th Street Major Collector East-West 2 30 Yes No Yes

1 Per VDOT Functional Classification map: http://www.virginiadot.org/projects/fxn_class/maps.asp (Reference 1)

2 Mph represents miles per hour

3 Joyce Street has a posted speed limit of 25 miles per hour south of Army Navy Drive and 35 miles per hour north of Army Navy Drive

4 On-street parking is available on Army Navy Drive west of Fern Street on the south side

As shown in Table 3, the street network in the study area is largely accommodating to urban traffic,

including a mostly comprehensive sidewalk network on all streets and available on-street parking.

The parcels to the north of Army Navy Drive and south of I-395 are mostly surface parking lots, largely

utilized by Pentagon employees. The parcels south of Army Navy Drive are mostly commercial uses

including Pentagon City Mall.

Pedestrian and Bicycle Facilities

Nearly all roadways within the network have pedestrian facilities including sidewalks and crosswalks at

intersections.

Currently Army Navy Drive has no dedicated bicycle facilities; however, three of the major north-south

streets have striped bicycle lanes. Joyce Street and Hayes Street have bicycle lanes on either side of the

street that terminate at Army Navy Drive. Eads Street has a two-way bike lane facility on the west side

of the street. These north-south connections currently end at a major east-west route in Army Navy

Drive leaving cyclists “stranded” without dedicated facilities to proceed. This circumstance provides

http://www.virginiadot.org/projects/fxn_class/maps.asp

22

further justification for implementing an east-west facility on Army Navy Drive that would link the trail

connection near Long Bridge Park to the Columbia Pike/S Joyce Street intersection.

TRANSIT FACILITIES

Army Navy Drive currently has six bus stops along the corridor; four westbound stops, and two

eastbound stops. These are simple curb-side signed stops, some providing bus shelters for passengers.

Along Hayes Street is a dedicated bus pull-out stops between Army Navy Drive and 15th Street which

services the Pentagon City Mall and surrounding commercial uses and serves as a connection point to

the Pentagon City METRO station at Hayes Street and 12th Street. Bus routes and stops also run along

Joyce Street and Eads Street.

EXISTING CONDITIONS TRAFFIC ANALYSIS

The traffic study began with developing existing conditions models to provide a datum comparison to

future scenarios. The development of these existing conditions models (for Year 2015 weekday a.m.

and p.m. peak-hour periods) first required a calibration effort to assess how closely the model

replicates real-world conditions. Following the calibration effort, operational performance metrics were

collected and summarized.

Existing Conditions Calibration

Developing existing conditions models requires honing in on key operations and effects that best

replicate real-world conditions in an effort to provide a simulated scenario that is comparable to actual

traffic experiences. The calibration effort was conducted to focus on the following elements per

guidance from the VDOT TOSAM (Reference 2):

Capacity (traffic volumes) – compares the traffic volumes processed at intersections within the

model to turning movement counts collected in the field.

Travel Times – compares simulated vehicle travel times to those collected in the field along

specified routes.

Spot Speeds – compares average vehicle speeds at point locations between simulated vehicles

and vehicle speed data collected in the field.

Visual Calibration – compares qualitative traffic patterns, observed in the field, that have

notable influence on the traffic operations in the study area (e.g. queuing, yielding behavior).

Achieving specified targets across these elements have been agreed to be sufficient to consider the

existing conditions models as acceptable representations of real-world traffic conditions. The details of

the calibration process and target achievement are found in the Calibration Summary Memorandum in

Appendix A.

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Existing Peak Hour Traffic Operations

Existing conditions models were run 10 times each using random vehicle seeding to produce varying

vehicle arrivals in the model. Operational performance metrics were captured for average vehicle delay,

the corresponding Level of Service (LOS), and maximum simulated queue lengths. Figure 8 and Figure 9

summarize the existing conditions intersection operational results during the weekday a.m. and p.m.

peak hours.

Table 4 summarizes the intersection delay and LOS results for the study intersections during the

weekday a.m. and p.m. peak periods under existing traffic conditions. These results were compared

against intersection delay and LOS results presented in the Synchro 9 models prepared by the County.

Table 4 Existing Peak Hour Conditions - Intersection Delay and LOS

Intersection

AM PM

VISSIM Synchro (HCM 2000) VISSIM Synchro (HCM 2000)

Delay LOS Delay LOS Delay LOS Delay LOS

Army Navy Drive & Joyce 21.2 C 19.8 B 26.0 C 26.0 C

Army Navy & Pentagon Mall 24.0 C 14.6 B 17.2 B 14.6 B

Army Navy & Hayes 33.2 C 48.5 D 24.5 C 43.1 D

Army Navy & Fern 18.8 B 13.9 B 22.7 C 21.4 C

Army Navy & Eads 32.9 C 23.7 C 41.3 D 19.5 B

Army Navy & 12th1 51.9 F 239.5 F 11.2 B 25.4 D

Joyce & North Driveway 19.6 C 13.2 B 16.1 C 18.5 C

12th & Hayes 30.6 C 10.3 B 12.8 B 21.6 C

12th & Fern 15.4 B 17.1 B 17.4 B 19.6 B

12th & Eads 12.0 B 8.5 A 14.0 B 12.1 B

1Unsignalized Intersection

Overall, study intersections simulated comparably operate as expected when compared to the Synchro

analysis results. Deviations from Synchro are largely attributed to VISSIM using a measured delay rather

than a formulaic calculation as done in deterministic methodologies like Synchro. These minimum

deviations suggest that the existing a.m. and p.m. peak models are operating as expected. Appendix B

contains the complete set of operational results and model output data for existing conditions.

26

EXISTING CONDITIONS FINDINGS

The operational analysis of existing traffic conditions identified several intersections and movements

that experience long queues, traffic congestion, and turning movements that operate at LOS F.

Army Navy Road/Eads Street

o Eastbound left-turn movement operates at LOS F during p.m. peak hour.

12th Street / Hayes Street

o Southbound left-turn movement operates at LOS F during a.m. peak hour.

Army Navy Road/12th Street

o The critical movement at the Army Navy Drive and 12th Street intersection is the

southbound left-turn, which operates at LOS F during the a.m. peak hour. This is due to

a combination of factors including southbound left-turn demand and a limited number

of gaps in traffic on eastbound 12th Street because of traffic volumes. The vehicle delays

contribute to queue build-up, which was determined from the VISSIM simulation to be

nearly 766 feet at the maximum simulated measurement during the a.m. peak hour.

o Field observation indicates that the southbound left-turning vehicles generally perform

a “rolling” stop when there’s no opposing traffic (most do not fully stop). The queue

accumulates pretty quickly from a platoon of eastbound vehicles arriving at the stop bar

when a pedestrian or a vehicle on 12th is using the intersection, but then the queue is

processed pretty readily. Vehicles do not make a full-stop and just slow down and treat

the stop sign as a yield sign. The developed simulation model well captured drivers’

behavior at this location and reflected the actual operational conditions.

o These results correspond well to visual observations of queuing during field visits. Traffic

congestion and queuing at this intersection is substantially less during the p.m. peak

hour.

Army Navy Drive/Hayes Street

o Southbound left-turning queues of approximately 1,085 feet were observed to extend

back on the off-ramp during the weekday a.m. peak hour. The queue was observed to

increase as demand on the eastbound approach of I-395 increased. No queue spill-back

onto the freeway was observed during the simulation.

o In short, both a.m. and p.m. scenarios indicate that the queues at southbound Hayes

Street can be accommodated within the existing off-ramp storage capacity. The a.m.

peak period experiences the longest queues from the freeways.

General findings

o Simulation results match with the field observations of queues and driver behavior.

o All intersections simulated comparably operate as expected when compared to the

Synchro analysis results.

SECTION 4

Travel Demand Modeling

29

TRAVEL DEMAND MODELING

The Metropolitan Washington Council of Governments’ (MWCOG) travel demand model was used in

this study as a tool for projecting future traffic volumes for the Army Navy Drive Traffic Study.

Modifications were made, driven by validation assessments, to the model network within the Army

Navy Drive study area in order to improve the accuracy of the model output. This resulted in the model

output more adequately reflecting conditions in the field. The traffic volumes forecast by the modified

model in the base year of 2015 compare favorably with the turning movement counts in the field. Such

measures of model performance as the percentages of differences in volumes and the root-mean

square estimate (RMSE) of the modified model are much better than the original model. An NCHRP 255

analysis was then conducted to develop turning-movement volumes for more in-depth traffic

operations evaluation for the 2020 and 2040 conditions This section provides a summary of the model

modifications, the future year model (2020 and 2040) conditions and the results of the NCHRP 255

analysis.

NETWORK MODIFICATIONS – 2015 MODEL

Numerous inconsistencies were found in the 2015 travel demand model, including incorrect number of

travel lanes, improper coding of links (e.g., incorrect link connections or links coded at incorrect places),

Traffic Analysis Zones (TAZs), and centroid connectors. The MWCOG model network also did not include

some key links needed for the Army Navy Drive study area. KAI added or extended individual streets so

that relevant study intersections and links would be represented in the network. By applying these

modifications, the network in the study area more-closely represented the actual highway network.

The network modifications were then tested for the 2015 base year. Once a satisfactory validation was

obtained, these were applied to the 2020 and 2040 model networks. The detailed summary of the

network modifications is attached in Appendix B. Figure 10 shows the modified MWCOG model

network of the Army Navy Drive study area. Figure 11 shows the original MWCOG model network of

the Army Navy Drive study area.

30

Figure 10 – Modified Network in Army Navy Drive Study Area

31

Figure 11 – Original Network in Army Navy Drive Study Area

The changes made to the network significantly improved the comparison of the 2015 model output for

the a.m. and p.m. peak hours with the field counts (i.e., traffic turning movement counts). The detailed

output model volumes in the study area are attached in Appendix D. Table 5 summarizes the total link

volume differences and the RMSE for the Army Navy Drive study corridor (i.e., Army Navy from S Joyce

St and 12th St S) for the a.m. peak hour and p.m. peak hour, respectively. As shown in the table, the

total model volume in the modified model is close to the turning movement counts (within 5% range).

The percentage of difference and RMSE of the modified model are much better than the original model.

The link-level comparisons of model volumes and field measurements are attached in Appendix E.

Table 5 Two-way Volume Comparison for Army Navy Drive

Peak Hour Field Count

Original Model Modified Model

Model Volume Percent %RMSE Model Volume Percent %RMSE

AM 16,349 11,291 -31% 71% 17,141 5% 39%

PM 17,942 13,102 -27% 52% 17,484 -3% 29%

32

Although the final fit between the model volumes and the counts is much improved, some movements

at individual intersections are still significantly off from the field observations. Therefore, the NCHRP

255 method was used later to develop the VISSIM inputs instead of directly using the volume

forecasted by the regional travel demand model. Based on the link volumes forecasted by the regional

travel demand model, growth rates were calculated through the NCHRP 255 method and the growth

rates were then applied on the corresponding field observations to forecast the future conditions.

It should be noted that the MWCOG travel demand model only produces peak period (a.m. and p.m.)

traffic volumes. The peak hour traffic volumes used in this study were calculated based on the peak-

hour factors suggested by the MWCOG travel demand model: 41.7% for the a.m. peak hour and 29.4%

for the p.m. peak hour. The project team also calculated the peak-hour factors (i.e., peak hour

volume/peak period volume) based on two tube-count locations on Army Navy Drive (between S Hayes

Street and S Fern Street, and between S Eads Street and 12th Street S). This was done in order to

validate the values suggested by the model. According to the tube counts, the corresponding peak hour

factors are 42.0% (average of 39% and 45%) for a.m. peak hour and 29.0% (average of 28% and 30%)

for p.m. peak hour. This correlates well with the values used in the MWCOG travel demand model.

STUDY AREA CONDITIONS – 2020 MODEL

As previously stated, the network modifications applied in the 2015 model above were also included in

the 2020 model network. The detailed 2020 model volumes in the study area are attached in Appendix

E. In order for more in-depth traffic operations evaluation for the 2020, turning movement counts were

developed using the NCHRP 255 procedure for the intersections along Army Navy Drive. These turning

movement volumes were then adjusted for analysis purposes in the following ways:

Traffic volumes were rounded to the nearest five vehicles per hour;

Traffic volumes were balanced between each pair of adjacent intersections; and,

In cases where existing volumes exceeded the developed NCHRP 255 volumes, the existing

volumes were used for analysis (i.e. all volumes were assumed to either increase or remain

unchanged between the existing year and 2040).

Appendix E summarizes 2020 model volumes and the corresponding turning-movement volumes

developed by the NCHRP 255 procedure for a.m. peak hour and p.m. peak hour, respectively.

STUDY AREA CONDITIONS – 2040 MODEL

As with the 2020 model, the network modifications applied in the 2015 model were applied to the 2040

model network. The 2040 turning-movement volumes of the intersections along Army Navy Drive were

also developed using the NCHRP 255 procedure. The detailed 2040 model volumes in the study area are

attached in Appendix E.

SECTION 5

Design Concept Refi nement

35

DESIGN CONCEPT REFINEMENT

INITIAL DESIGN CONCEPT

The initial Design Concept called for improvements to Army Navy Drive between Joyce Street and 12th

Street including:

Median transit lanes between Joyce Street and Hayes Street.

Protected bike lanes on the south side of Army Navy Drive from Joyce Street to 12th Street.

Incorporation of a transit facility between Joyce Street and the Parking Garage Driveway.

INITIAL OBSERVATIONS

KAI conducted an initial screening of the concept, and developed a list of observations to consider prior

to modeling (as depicted in Figure 12). These included transit (blue), vehicular (red), bicycle (green),

and pedestrian (yellow) considerations. Major takeaways included:

Bicycle treatments should be further evaluated to address the following observations:

o Conflicts could exist between bicycle movements and other modes at the

intersections, requiring exclusive bicycle phases.

o The location of the protected bike lanes could cause confusion for inexperienced

cyclists attempting to enter and exit the facility.

o Conflicts between right-turning vehicles and bicyclists in the protected bike lanes

could exist.

The median transit lanes should be further evaluated to address the following observations:

o Conflicts could exist between bus movements and other modes at the intersections,

requiring exclusive transit phases.

o Mixed traffic could accidentally enter the median transit lanes, particularly at Joyce

Street and Hayes Street where buses would be turning into and out of the lanes.

o Transit stops located in the median could cause confusion for riders.

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Figure 12 – Initial Design Concept Considerations

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BICYCLE TREATMENTS

Based on initial observations, consideration was given to moving the protected bike lanes to the north

side of Army Navy Drive or into the median (in place of the transit lanes). However, the decision was

made to keep the protected bicycle lanes on the south side of the corridor for the following reasons:

Keeping the protected bike lanes on the south side of Army Navy Drive (versus the north

side) provides easier access to the major commercial developments in the area.

Having the protected bike lanes on the south side of the corridor (versus the median) also

provides flexibility with the signal equipment. It allows bicyclists moving into and out of the

facility to progress with vehicular traffic without the use of bicycle signal heads and

exclusive bicycle phases. Conflicts between bicycles and other modes can be reduced

through the use of bike boxes.

The observations related to conflicts between bicycles and other modes should be fully resolved in the

design phase. Guidance will be required for bicyclists as well as other modes as they interact with the

protected bike lanes.

The remainder of the operational analysis was conducted assuming that the protected bike lanes will be

located on the south side of Army Navy Drive.

TRANSIT TREATMENTS

Two concepts were ultimately evaluated for the exclusive transit lanes – (1) median transit lanes and (2)

outside transit lanes. Both concepts were evaluated using critical movement analysis for existing a.m.

and p.m. volumes. Critical movement analysis not only provided insights into the potential conflicts at

the intersections, but also provided an estimated cycle length that would be required to accommodate

demand. This type of analysis is only planning-level, and many assumptions (outlined in Appendix F)

had to be made; critical movement analysis was beneficial because it provided a quick method for

comparing the alternatives.

As expected from the initial observations, there were many conflicts between buses and other modes

when considering the median transit lanes. These conflicts required exclusive transit phases, which

increased cycle lengths, as well as lane-configuration revisions at some of the intersections. In order to

fully vet the concept, outside transit lanes were also evaluated.

While a full assessment of all five intersections in the study area was completed (available in Appendix

F), this section focuses on Joyce Street, the Parking Garage Driveway, and Hayes Street. The concepts

remain the same at Fern Street and Eads Street, so those intersections had less influence on the

location of the transit facility.

38

Median-Transit-Lanes Concept

In addition to the location of the transit lanes, a decision had to be made about which buses would use

the transit lanes. There are high-capacity buses that run along Army Navy Drive. These travel to/from

the north leg of Joyce Street, turn onto Army Navy Drive, and travel to/from the south leg of Hayes

Street. In order for the exclusive transit lanes to be most effective, all buses along the corridor would

need to utilize them (not just the high-capacity buses).

However, several scenarios were evaluated using critical movement analysis, in order to assess the

effect of high-capacity buses versus all buses using the transit facility:

Median-transit-lanes concept with high-capacity buses

Median-transit-lanes concept with all buses

Revised lane configuration with high-capacity buses

Revised lane configuration with all buses

The revised-lane-configuration scenarios incorporate changes at several intersections to reduce

conflicts between modes and ultimately decrease the required cycle length. Revisions included in these

scenarios are listed in Table 6.

Table 6 Lane-Configuration Revisions for Median-Transit-Lanes Concept

Intersection Lane-Configuration Revision Reason for Recommended Change

Parking Garage Driveway

Changed eastbound approach to left and through-right lanes (instead of left-through and through-right lanes)

Left-turn lane is required unless split phasing is used on the eastbound and westbound approaches

Changed northbound approach to left, through, and dual right lanes (instead of left, left-through, and right lanes)

Using left and through lanes is better for driver expectations

Dual right-turn lanes reflect existing conditions at the parking garage

Changed southbound approach to left and through-right lanes (instead of left-through and right lanes)

Using left and through-right lanes is better for driver expectations

Hayes Street Reversed right-turn lane and bike lane (so that bike lane is on the outside)

With the protected bike lanes on the south side of Army Navy Drive, weaving would occur between vehicles and bicycles with the right-turn lane on the outside

Table 7 summarizes the increase or decrease in cycle length that would be required to accommodate

demand during the a.m. and p.m. peaks for each of the scenarios. Most of the scenarios require an

increase in cycle length to accommodate demand. This is expected because the number of through

lanes along the corridor has been reduced to provide space for the exclusive transit lanes.

Most likely, median transit lanes would have all buses using the facility (as shown in Figure 13, Figure

14, and Figure 15) and would require lane-configuration revisions. In particular, revisions would be

required at the Parking Garage Driveway. Without left-turn lanes, the eastbound and westbound

movements would have to be split phase, so that left-turning vehicles would not conflict with buses in

the exclusive transit lanes. This drives the cycle length up to nearly 180 seconds in the p.m. peak (using

39

only existing volumes). In order to provide a more-reasonable cycle length, eastbound and westbound

left-turn lanes would be required. However, this would reduce the eastbound through movement to

one lane.

Table 7 Estimated Cycle-Length Increase or Decrease (in Seconds Compared to Existing Conditions) Required to Accommodate Demand with Median Transit Lanes

Concept

Joyce Street Parking Garage Driveway Hayes Street

AM PM AM PM AM PM

Existing Condition 100 100 100 100 100 100

Median-Transit-Lanes Concept with High-Capacity Buses +14 +10 +57 +77 +45 +43

Median-Transit-Lanes Concept with All Buses +31 +29 +57 +77 +69 +73

Revised Lane Configuration with High-Capacity Buses +14 +10 +6 -11 +45 +43

Revised Lane Configuration with All Buses +31 +29 +6 -11 +69 +73

Figure 13 – S Joyce Street Median Transit-Lanes Concept Movements

40

Figure 14 – Parking Garage Driveway Median-Transit-Lanes Concept Movements

Figure 15 – S Hayes Street Median-Transit-Lanes Concept Movements

41

Outside-Transit-Lanes Concept

Reducing the eastbound through movement down to one lane, as required in the median-transit-lanes

concept, may not be possible because of queuing. An outside-transit-lanes concept was assessed to

determine if major lane-configuration revisions could be avoided. Again, several scenarios were

evaluated using critical movement analysis:

Outside-transit-lanes concept with high-capacity buses

Outside-transit-lanes concept with all buses

Revised lane configuration with high-capacity buses

Revised lane configuration with all buses

The revised-lane-configuration scenarios incorporate changes at several intersections to reduce

conflicts between modes and ultimately decrease the required cycle length. Revisions included in these

scenarios are listed in Table 8.

Table 8 Lane-Configuration Revisions for Median-Transit-Lanes Concept

Intersection Lane-Configuration Revision Reason for Recommended Change

Parking Garage Driveway

Changed northbound approach to left, through, and dual right lanes (instead of left, left-through, and right lanes)*

Using left and through lanes is better for driver expectations

Dual right-turn lanes reflect existing conditions at the parking garage

Changed southbound approach to left and through-right lanes (instead of left-through and right lanes)*

Using left and through-right lanes is better for driver expectations

Hayes Street Reversed right-turn lane and bike lane (so that bike lane is on the outside)

With the protected bike lanes on the south side of Army Navy Drive, weaving would occur between vehicles and bicycles with the right-turn lane on the outside

*Lanes have since been reconfigured for the ultimate concept; see Geometric Recommendations for details.

Unlike the median-transit-lanes concept, the outside-transit-lanes concept assumes that the transit

lanes will be shared with right-turning vehicles. Therefore, only high-capacity buses will likely utilize the

transit facility; other buses (not turning to/from the north leg at Joyce Street or the south leg at Hayes

Street) will utilize the traditional travel lanes. If all buses were to use the transit facility, right-turning

vehicles could experience long delays waiting behind buses requesting exclusive transit phases. Transit

will still be receiving a benefit from the right-turn-only/transit lanes, but the benefit will not be as high

as with exclusive transit lanes.

Table 9 summarizes the increase or decrease in cycle length that would be required to accommodate

demand during the a.m. and p.m. peaks for the four scenarios listed above. The values that are less

than those under the median-transit-lanes concept are highlighted in green. It is clear from the table

that significant benefit can be achieved at the Parking Garage Driveway with the outside transit lanes.

This concept allows buses to travel with vehicular traffic because left-turning vehicles do not conflict

with through bus movements.

42

Most likely, outside transit lanes would have only high-capacity buses using the facility (as shown in

Figure 16, Figure 17, and Figure 18) and would not require lane-configuration revisions to reduce the

cycle length. Ring-and-barrier diagrams for this concept (for Joyce Street, the Parking Garage Driveway,

and Hayes Street), developed in preparation for modeling, are shown in Figure 19, Figure 20, and Figure

21.

Table 9 Estimated Cycle-Length Increase or Decrease (in Seconds Compared to Existing Conditions) Required to Accommodate Demand with Outside Transit Lanes

Concept

Joyce Street Parking Garage Driveway Hayes Street

AM PM AM PM AM PM

Existing Condition 100 100 100 100 100 100

Outside-Transit-Lanes Concept with High-Capacity Buses +14 +10 +40 +29 +45 +43

Outside-Transit-Lanes Concept with All Buses +31 +27 +40 +29 +69 +73

Revised Lane Configuration with High-Capacity Buses +14 +10 -4 -11 +45 +43

Revised Lane Configuration with All Buses +31 +27 -4 -11 +69 +73

Note: Table cells highlighted in green represent values that are lower with outside transit lanes than with median transit lanes.

Figure 16 – S Joyce Street Outside-Transit-Lanes Concept Movements

43

Figure 17 – Parking Garage Driveway Outside-Transit-Lanes Concept Movements

Figure 18 – S Hayes Street Outside-Transit-Lanes Concept Movements

44

Figure 19 – Joyce Street AM (left) and PM (right) Ring-and-Barrier

Figure 20 – Joyce Street AM (left) and PM (right) Ring-and-Barrier

45

Figure 21 – Hayes Street AM (left) and PM (right) Ring-and-Barrier

QUALITATIVE EVALUATION

While the results of the critical movement analysis are a key component of the Design Concept

evaluation, there were several other metrics used to assess the advantages and disadvantages of the

transit facility concepts. Table 10 summarizes the evaluation criteria used to qualitatively assess

whether a slight or significant advantage was anticipated with median or outside transit lanes. The

following categories were assessed:

Vehicle operations

Transit operations

Conflicts at intersections

Conflicts along segments

User expectations at intersections

User expectations along segments

46

Table 10 Evaluation of Median and Outside Transit Lanes

Evaluation Criteria

Median Transit Lanes

Outside Transit Lanes Notes

Vehicle Operations ✔

Fewer transit-only phases are required with outside transit lanes (particularly at the Parking Garage intersection), which results in more time for other vehicles during the cycle.

Combining the transit and right-turn lanes on the outside allows extra cross-section space to be used for other movements, increasing capacity for vehicles in those lanes.

Transit Operations ✔ Inside transit lanes are exclusive transit lanes, resulting in more-reliable travel times

for buses (i.e. more-consistent headways).

However, with outside transit lanes, transit can run concurrently with additional vehicle movements, meaning transit receives more green time during the cycle.

Minimize Conflicts at Intersections ✔

Buses using outside transit lanes conflict with fewer vehicle movements at intersections. In other words, outside transit can run concurrently with adjacent left-turning, through, and right-turning traffic, but inside transit must often utilize a transit-only phase.

Inside transit lanes create the potential for vehicles to accidentally turn into the transit lanes, which are median-separated.

Minimize Conflicts Along Segments ✔

Outside transit lanes create the potential for weaving maneuvers into and out of the right-turn-only/transit lanes.

Buses using outside transit lanes may block other drivers’ view of contraflow bicycles.

User Expectations at Intersections ✔

Bus drivers would be making atypical movements from inside transit lanes, requiring transit-only signals.

Inside transit lanes would require guidance to prevent vehicles from following buses into the transit lanes.

User Expectations Along Segments ✔

Outside transit lanes would allow for more-conventional, curbside bus stops.

OVERALL ✔

LEGEND ✔ = Significant Advantage ✔ = Slight Advantage

CONCEPT REFINEMENT

Based on the results of the critical movement analysis and qualitative evaluation, the County decided

that the outside-transit-lane concept should be modeled. The following changes were made to the

initial Design Concept:

Transit lanes were moved to the outside lanes between Joyce Street and Hayes Street.

Transit lanes will also serve right-turning vehicles by restricting through vehicles (except for

buses) at the intersections.

Bicyclists leaving the protected bike lanes on the south side of Army Navy Drive from Joyce

Street to 12th Street will utilize bike boxes and run concurrently with vehicular traffic.

Some of the additional lane-configuration revisions listed in Table 8 were not incorporated into the

revised concept but should be considered in the design phase.

SECTION 6

Future Conditions Analysis

49

FUTURE CONDITIONS ANALYSIS

Understanding how implementing the Design Concept will affect traffic conditions in the future aids in

identifying potential flaws in the design that would not be captured under current conditions.

Background developments within the study area were also considered. It should be noted that the I-395

HOT lanes and associated improvements were not included in the analysis.

BACKGROUND DEVELOPMENTS

For future year analyses, background infrastructure and land-use developments were included to

account for their impact to the traffic network. Future planning accounts for the completion of 12th

Street S between Fern Street and Eads Street and there are three notable developments anticipated to

affect the Study: the Pentagon Transit Center, PenPlace, and 400 Army Navy Drive. Figure 22 shows the

locations of these developments within the study area. Site plans for all developments can be found in

Appendix G.

Figure 22 – Location of Background Developments

12th Street Completion/Transit Facility

The most notable infrastructure improvement is the completion of the 12th Street South alignment

between Fern Street and Eads Street, which had not been constructed at the time this study began

(construction completed in 2016). This connection has been modeled as a two-lane cross-section

(consistent with the blocks on either end). In addition to the connection between Fern Street and Eads

Street, 12th Street S was modified to accommodate a proposed median bus lane facility between Eads

Street and Clark Street, requiring Army Navy Drive/12th Street S to be signalized. This facility assumed a

50

single median transit lane and single all-traffic lane in each direction. Intersections at Eads Street and

Army Navy Drive were reconfigured to accommodate bus-only signal phasing, allowing buses to re-

integrate with traffic outside of the new bus facility. Details regarding the proposed configuration of

12th Street and the modeled signal phasing timing are included in Appendix I.

Pentagon Transit Center

The Pentagon and WMATA are developing a transit center at the northeast corner of S Joyce St/Army

Navy Drive. The transit center is in preliminary design by internal Pentagon staff. The current plans

show and 8-bay sawtooth design with the access to the center being directly adjacent to the Army Navy

Drive travel lanes. The operation of this center is currently under development, but is considered to be

used by WMATA, ART, commuter bus routes, and tourist buses.

PenPlace

Vornado/Charles E. Smith is in the process of developing a commercial complex, referred to as

PenPlace, just south of Army Navy Drive between Fern Street and Eads Street (Reference 3). The

PenPlace development is intended to retain the existing Marriott Residence Inn in the northwest

portion of the site and proposes four new office buildings and a hotel. The development fronts the

newly constructed connection of 12th Street South between Fern Street and Eads Street and an

additional two east-west access driveways. The total development anticipates adding 149 a.m. peak

trips (47 in, 102 out) and 235 p.m. peak trips (131 in, 104 outs).

400 Army Navy Drive

The site at 400 Army Navy Drive (positioned at the southeast corner of Army Navy Drive/S Eads St) is

planned for redeveloping the existing 235,000 square-foot office building with a 452 unit multi-family

residential development (Reference 4). The redevelopment does not propose the construction of any

new access driveways onto Army Navy Drive or S Eads St. The total development anticipates reducing

the total number of a.m. and p.m. peak hour trips due to the change in land use from commercial office

to multi-family residential.

YEAR 2020 AND 2040 NO-BUILD

No-build scenario was developed and analyzed to forecast how the study network would operate at the

future planning horizon without the implementation of the Design Concept. Figure 23 shows the no-

build condition lane configuration and traffic control devices at the study intersections as modeled;

analysis began in 2015 prior to completion of 12th Street South. Figure 24 and Figure 25 summarize the

delay and LOS results for the study intersections during the weekday a.m. and p.m. peak periods under

2020 traffic conditions. Figure 26 and Figure 27 detail the 2040 no-build traffic operations results.

56

With increasing traffic demand in the year 2020 and 2040, traffic performance within the study area

will deteriorate. Individual intersection operations will vary from time period to time period due to

changes in traffic demands and adjustment to signal timing/phasing between future Years 2020 and

2040 (i.e. it is unlikely to see a consistent change in operations intersection-to-intersection between

analysis years). Under the no-build condition, congestion along Army Navy Drive is anticipated to

mostly be concentrated toward the east side of the corridor and focused around the Eads Street/Army

Navy Drive intersection. For both peak hours, Eads Street/Army Navy Drive is anticipated to operate at

LOS E/F in both Year 2020 and Year 2040. It is this center of congestion that spills to neighboring

intersections and is largely limited by the capacity of the vehicle trips destined northbound toward the

north I-395 on-ramp. Heavy eastbound left demands conflicting with heavy westbound through

demands (from the US 110 off-ramp and westbound Army Navy Drive traffic) result in limited protected

green time. All 2020 and 2040 no-build traffic operations results can be found in Appendix H. Overall

intersection operations are summarized in Table 12 and Table 13.

The operational analysis of no-build traffic conditions in Year 2020 identified intersection approaches

that continue experiencing long queues and traffic congestions that operate at LOS E or worse, which

are summarized below:

S Hayes Street/ Army Navy Drive

o Eastbound approach will operate at LOS F during the p.m. peak hour, driven by left- and

through- traffic demands.

o Northbound and southbound approaches will operate at LOS E during the a.m. peak

hour due to heavy left-turn volumes only being serviced by protected phases.


o Northbound approach will operate at LOS E during a.m. and p.m. peak hours, driven by

high left-turn demand as a side street.

o Eastbound approach will operate LOS E during the p.m. peak hour due to queue

spillback from Eads Street/Army Navy Drive limiting throughput.


o The overall intersection will operate at LOS E during the a.m. peak hour and LOS F

during the p.m. peak hour.

o Eastbound approach will operate at LOS F during a.m. and p.m. peak hours. Heavy left-

turn movement causes queue spillback along the approach and is unable to recover

within the peak hour. The shared left-through configuration also limits the capacity of

through vehicles.

o Westbound approach will operate at LOS F during the p.m. peak hour. Heavy demand

from the westbound approach conflicts with the eastbound left and needs to compete

for available green time with limited available geometric capacity.

o Southbound approach operates at LOS F during a.m. peak hour due to limited side-

street green time available.

o Northbound approach operates at LOS F during the p.m. peak hour due to limited side-

street green time and a single lane approach to Army Navy Drive.


57

o Congestion at this intersection is largely attributed to several factors: 1. All movements are designed to keep traffic flowing through two intersections

along 12th Street South (at Army Navy Drive and at Clark Street), requiring longer clearance intervals.

2. All movements have limited flexibility in allowable green time due to the two-intersection phasing.

3. The intersection (in conjunction with 12th Street S/Clark Street) has heavy relatively heavy turning volumes compared to through-volumes.

o The overall intersection will operate at LOS F during the a.m. and p.m. peak hours. o Eastbound approach will operate at LOS F during the a.m. peak hour. o Westbound approach will operate at LOS F during the a.m. and p.m. peak hours. o Southbound approach will operate at LOS E and over capacity during the a.m. peak

hour.

Noteworthy operational observations in the Year 2040 under no-build conditions include:


o Eastbound approach will operate at LOS E during the a.m. peak hour due to heavy

demand for all movements.


o The overall intersection will operate at LOS E during the a.m. peak hour.

o Westbound approach will operate at LOS F during the a.m. peak hour due to heavy left-

turn demands into the parking garage.


o The overall intersection will operate at LOS E during the a.m. peak hour.

o Eastbound approach will operate at LOS E during the p.m. peak period due to heavy left-

turn and through demand. The left-turn movement (toward I-395) is only processed

during a protected phase.

o Northbound approach will operate at LOS F during the a.m. peak period due to heavy

left-turn demand limited by a protected-only phase.

o Southbound approach will operate at LOS F/E during the a.m. and p.m. peak hours,

respectively. Heavy overall demand is the primary cause for high delays during the a.m.

peak hour. Heavy relative left-turn demand is the main cause during the p.m. peak hour.


o The overall intersection will operate at LOS E during the p.m. peak hour.

o Northbound approach will operate at LOS F during a.m. and p.m. peak hours, driven by

high overall demand as a side street.

o Eastbound approach will operate LOS F during the p.m. peak hour due to queue





58

o Eastbound approach will operate at LOS F during a.m. and p.m. peak hours. Heavy left-

turn movement causes queue spillback along the approach and is unable to recover

within the peak hour. The shared left/through configuration also limits the capacity of

through vehicles.




o Northbound approach operates at LOS F during the p.m. peak hour due to limited side

street green time and a single lane approach to Army Navy Drive.


o Congestion at this intersection is largely attributed to several factors: All movements are designed to keep traffic flowing through two intersections

along 12th Street S (at Army Navy Drive and at Clark Street), requiring longer clearance intervals.

All movements have limited flexibility in allowable green time due to the two-intersection phasing.

The intersection (in conjunction with 12th Street S/Clark Street) has heavy relatively heavy turning volumes compared to through-volumes.

o The overall intersection will operate at LOS E during the a.m. peak hour and LOS F during the p.m. peak hour.

o Eastbound approach will operate at LOS F during the a.m. peak hour. o Westbound approach will operate at LOS F during the a.m. and p.m. peak hours. o Southbound approach will operate at LOS E and over capacity during the a.m. and p.m.

peak hours.

General findings from peak hour operations in no-build conditions include:

Significant congestion was observed in both future years during both a.m. and p.m. peak

hours, notably at S Hayes Street, S Fern Street, S Eads Street and 12th Street intersections.



The observed bottleneck is the eastbound approach at S Eads Street/Army Navy Drive.

Current eastbound lane configuration is a left/through and through/right layout, which

negatively impacts the progression of left-turn and through movements. Future forecast

indicates heavy demands from all legs combined at this intersection with predominate

conflicts between eastbound left-turn movement and westbound through movement. With

heavy volumes destined to the northbound direction towards I-395, the limitation of having

a single receiving lane, congestion is not expected to be alleviated using only signal

timing/phasing improvements.

59

YEAR 2020 AND 2040 BUILD

Build scenario models were developed to account for both background development and the

implementation of the Design Concept. Figure 28 shows the future planning lane configuration and

traffic control devices at the study intersections. Figure 29 and Figure 30 show delay and LOS results for

the study intersections during the Year 2020 peak hours. Figure 31 and Figure 32 detail the 2040 build

traffic operations results.

The build condition limits capacity compared to the no-build condition by limiting the number of traffic

lanes that can be utilized by general traffic in favor of transit and bicycle facilities. Under build

conditions, the study network experiences notable increases in per-vehicle delay compared to existing

conditions as well as no-build conditions. This varies intersection-to-intersection, but is attributed to

the limited capacity from travel lanes being repurposed and subsequent signal timing/phasing

constraints. The most impacted intersections include: S Hayes Street, S Fern Street, S Eads Street and

12th Street, which generally exhibit a decrease in LOS from LOS D to LOS E/F during the peak hours.

Significant congestions in the build scenarios were observed resulting in extensive queues and cycle

failures along Army Navy Drive. All 2020 and 2040 build traffic operations results can be found in

Appendix H. Overall intersection operations are summarized in Table 12 and Table 13.

The operational analysis of build traffic conditions in Year 2020 identified intersection approaches that continue experiencing long queues and traffic congestions that operate at LOS E or worse, which are summarized below:


o Westbound approach will operate at LOS F during the p.m. peak hour due to heavy-left

turn demands into the parking garage.


o The overall intersection will operate at LOS E during the a.m. peak hour. o Eastbound approach will operate at LOS F during the a.m. peak hour due to heavy

through and right-turn volumes. Northbound approach will operate at LOS E due to high-left turn delay, limited by a protected only phase and heavy demand.

o Southbound approach will operate at LOS F during the a.m. peak hour. The a.m. peak hour delays are due to high overall demand on the approach.


o Westbound approach will operate at LOS E during the p.m. peak hour from overall heavy demand.

o Northbound approach will operate at LOS E during the a.m. peak hour and LOS F during the p.m. peak hour driven by high overall demand as a side street.


o The overall intersection will operate at LOS F during the p.m. peak hour. o Westbound approach operates at LOS F during the p.m. peak hour due to heavy through

demand competing with the conflict eastbound left-turn demand.

60

o Northbound and southbound approaches operate at LOS E/F during both a.m. and p.m. peak hours due to high overall demand as a side street. The northbound approach is limited due to the single lane along the approach and heavy left-turn movement spilling back.


o Congestion at this intersection is largely attributed to several factors: All movements are designed to keep traffic flowing through two intersections

along 12th Street South (at Army Navy Drive and at Clark Street), requiring longer clearance intervals.



o The overall intersection will operate at LOS E during the a.m. peak hour and LOS F during the p.m. peak hour.

o Eastbound approach will operate at LOS F during the a.m. peak hour.

o Westbound approach will operate at LOS F during the a.m. and p.m. peak hours.

o Southbound approach will operate at LOS E during the a.m. peak hour.

Noteworthy operational observations in the Year 2040 under build conditions include:

S Joyce Street /Army Navy Drive

o Westbound approach will operate at LOS E during the a.m. peak hour due to heavy left

turn demand limited by protected only phasing.

o Northbound approach will operate at LOS E during the p.m. peak hour due to high left

turn and through demands.

o Southbound approach will operate at LOS E during the a.m. peak hour due to high left



o The overall intersection will operate at LOS E during the a.m. peak hour

o Westbound approach will operate at LOS F during the a.m. peak hour due to heavy left



o The overall intersection will operate at LOS F during the a.m. peak hour and LOS E


o Northbound approach will operate at LOS F during a.m. peak hour and LOS E during the

p.m. peak hour due to heavy left turn demand limited by protected only phasing.

o Southbound approach will operate at LOS F during the a.m. and p.m. peak hours due to

heavy left turn demand.


o The overall intersection will operate at LOS E during the p.m. peak hour.

61

o Eastbound approach will operate at LOS E during the p.m. peak hour due to queue


o Westbound approach will operate at LOS E during the p.m. peak hour due to heavy left

turn and through demand.

o Northbound approach will operate at LOS F due to high overall demand as a side street.




o Eastbound approach will operate at LOS F during the a.m. and p.m. peak hours. Heavy

left turn volumes limited by protected only phasing and heavy conflicting westbound

through volumes.




o Northbound approach operates at LOS E during the a.m. peak hour and LOS F during the

p.m. peak hour due to limited side street green time and a single lane approach to Army

Navy Drive.

o Southbound approach operates at LOS E during the a.m. and p.m. peak hours due to

high overall demand as a side street.


o Congestion at this intersection is largely attributed to several factors: All movements are designed to keep traffic flowing through two intersections along

12th Street South (at Army Navy Drive and at Clark Street), requiring longer clearance intervals.



o The overall intersection will operate at LOS F during the a.m. and p.m. peak hours. o Eastbound approach will operate at LOS E during the a.m. and p.m. peak hours. o Westbound approach will operate at LOS E during the a.m. peak hour and LOS F during

the p.m. peak hour. o Northbound approach will operate at LOS E during the p.m. peak hour. o Southbound approach will operate at LOS F during the a.m. peak hour and LOS E during

p.m. peak hour.

General findings from peak hour operations in build conditions include:

Significant congestion was observed in both future years during both a.m. and p.m. peak

hours, notably at S Hayes Street, S Fern Street, S Eads Street, and 12th Street S intersections.



The observed network bottlenecks, like the no-build conditions are the S Eads Street/Army

Navy Drive intersection.

62

o Future forecast indicates heavy demands from all legs combined at this intersection

with predominate conflicts between eastbound left-turn movement and westbound

through movement. With heavy volumes destined to the northbound direction towards

I-395, the limitation of having a single receiving lane, congestion is not expected to be

alleviated using only signal timing/phasing improvements.

o Queue storage along for the eastbound left-turn is recommended to be extended as far

as possible, but block spacing remains a limiting factor. Even with maximum storage,

left-turn queue spillback is anticipated.

The overall Design Concept limits capacity along Army Navy Drive, reducing general traffic

lanes in favor of transit and bicycle facilities.

68

COMPARISON ACROSS ALL SCENARIOS

This section provides a comparison assessment of peak-hour operations of the study network across all

scenarios including: existing, no-build, and build conditions.

Network Wide Performance

The variability of signalized arterial networks makes analysis of individual intersections difficult to

evaluate overall traffic operations. Because intersections are closely spaced (generally around 600-ft,

stop bar-to-stop bar), a variety of factors affect individual intersection performance that may not be

indicative of actual traffic conditions, including:

Variations in signal timing/phasing;

Platoon progression, and;

Impacts of residual queues/queue spillback.

To better understand the operational impact of the Design Concept, network-wide performance

measures are examined including average delay, total travel times, and spot speeds. The following

section and graphs demonstrate these network level performance measures across the different

analyzed scenarios. The general trends show network performance decreases over time from existing

(2015) to future year conditions (2020 and 2040), producing increased vehicle delay, increased travel

time, and decreased spot speeds. Similar patterns were observed comparing no-build models to build

models in that the limited roadway capacity in the build model showed a decrease in network

performance compared to the accompanying no-build.

Average Network Delay

One parameter worth examining is the average network delay experienced by drivers under different

scenarios. Average network delay is calculated from the total delay measured in the study network

divided by the total user throughput. The total throughput can include all users, as shown in Figure 33,

or be refined to different vehicle classes like passenger cars (Figure 34) and transit (Figure 35).

Percentages above the bars in the graph indicate the percent change when comparing the build

scenario to the corresponding no-build scenario.

69

Figure 33 – Average Network Delay for All Vehicles by Scenario

Comparing the impact of the build scenario, there is an estimated increase of approximately 7-27% in

average network delay for all vehicles (compared to the no-build scenario). Temporal comparisons

between Year 2020 and Year 2040 show an estimated increase of approximately 16-46% in average

network delay.

Figure 34 – Average Network Delay for Passenger Cars by Scenario

0

50

100

150

200

250

300

2015 2020 2040 2015 2020 2040

All All

AM PM

Ave

rage

De

lay

(se

c/ve

h)

No-Build Existing Build

0

50

100

150

200

250

2015 2020 2040 2015 2020 2040

Cars Cars

AM PM

Ave

rage

De

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(se

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h)


+7.3%

+26.9% +24.3%

+17.5%

-0.2%

+32.8%

+29.0%

+21.2%

70

Figure 35 – Average Network Delay for Transit by Scenario

Similar patterns follow when examining general traffic and transit-specific network-wide delay. The

transit delays increase in the build versus the no-build scenario and is further examined in the section

below.

Transit Route Travel Times

Examining more-specific travel times (particularly for transit) can help explain the impact of difference

scenarios to individual transit routes. Considering the multi-modal goals of the Design Concept,

examining these routes will provide better insight to the Design Concept’s efficacy of facilitating better

transit service.

Table 11 summarizes the transit travel times between S Joyce Street and S Eads Street during the peak

periods. Transit travel times generally increased in the build condition, despite the presence of a

dedicated lane.

0

50

100

150

200

250

300

2015 2020 2040 2015 2020 2040

Transit Transit

AM PM

Ave

rage

De

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(se

c/ve

h)


+16.6% +24.7%

+9.6%

+4.1%

71

Table 11 Transit Travel Times

Direction Route AM Peak Hour

Existing 2020 No Build 2020 Build 2040 No Build 2040 Build

Eastbound Joyce to Hayes* 178.0 203.6 343.5 221.6 226.2

Hayes to Eads* 63.2 213.0 87.0 183.9 170.0

Westbound Eads to Hayes N/A N/A 157.2 N/A 182.9

Hayes to Joyce 93.1 118.2 112.0 131.4 145.3

Direction Route PM Peak Hour

Existing 2020 No Build 2020 Build 2040 No Build 2040 Build

Eastbound Joyce to Hayes 169.7 182.6 185.6 184.2 163.7

Hayes to Eads 130.3 274.7 103.0 298.3 247.2

Westbound Eads to Hayes* N/A N/A 168.8 N/A 171.5

Hayes to Joyce* 146.4 62.7 93.6 77.1 105.4

*indicates peak direction

Despite transit facilities being included under the build scenario, transit travel times increase with

transit-only lanes, specifically on the segments with those transit only lanes. This is attributed to the

Design Concept (and model) using these lanes as transit and right turns only. Figure 36 summarizes the

eastbound challenges with this situation as it terminates at S Hayes Street.

Figure 36 - Summary of Transit Travel Time Increases at S Hayes St/Army Navy Dr

What commonly happens is the following:

The EB right turns are delayed by cyclists and pedestrians, causing queues that extend to and beyond the near-side bus stop.

72

For buses departing the stop: EB queuing at the stop bar in adjacent through lanes block buses to the curbside lane; 20 buses during the a.m. peak hour need to merge to the adjacent through lane to continue EB (an additional 8 buses turn right during the a.m. peak hour).

For buses approaching the stop: The EB queues will extend beyond the bus stop, preventing buses from reaching to the near-side stop (first stop) until the standing queue clears the intersection. Then second stop occurs at the stop for boarding/alighting.

In other words, the transit lane is essentially a trap lane for over 70% of buses that continue EB on Army

Navy Drive, and the factors described above result in a notable increase in bus travel time. By contrast,

the no-build benefits from continuity of receiving lanes, and no conflicting cycle track. Some potential

mitigation strategies may include:

Relocating the bus stop further west to limit the extend of the queue or extending the bus stop platform to allow buses to dwell while getting blocked by the standing queue

Providing a receiving lane on the east side of S Hayes Street (which has its own limitations)

As a result, the transit only lanes only partially mitigate the impact of reducing the number of general

purpose traffic lanes. The transit only lanes are still recommended for implementation despite not

being able to maximize the potential benefit of continuous lanes from S Joyce Street through S Eads

Street.

Spot Speed

Spot speeds serve as a proxy measure of traffic flow at collected locations within the network. Rather

than the actual value of individual spot speeds, analyzing the “spread” of average spot speeds by

scenario can be an indication of each scenario’s impact to that particular location in the network. For

example, tightly clustered spot speed results indicate that there is little effect between scenarios at that

particular location. By contrast, a larger spread of average spot speeds (by scenario) would indicate a

particular location where the conditions of that scenario have a larger impact.

Figure 37 and Figure 38 show the simulation results of average spot speeds collected by scenario,

during the a.m. and p.m. peak hours, respectively. Generally, the congestion of the a.m. peak hour

seems to be relatively consistent across scenarios. The speed spreads during the p.m. peak hour,

indicating notable impacts of the Design Concept on the eastern side of the corridor (east of S Hayes

Street). No significant speed changes were observed along northbound Joyce Street or northbound S

Hayes Street during either peak hour.

73

Figure 37 – Spot Speeds during AM Peak Hour

Figure 38 – Spot Speeds during PM Peak Hour

Individual Intersection Performance

While network-wide performance measures can provide insight regarding the overall impact of a

scenario, examining individual intersection performance metrics can provide some detailed information

regarding network bottlenecks and challenges. Table 12, Table 13, Figure 39 and Figure 40 summarize

intersection control delay across all scenarios. Intersection-level performance metrics continue a trend

of worsening operations from existing to future conditions.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

NB Joyce St SB Joyce St WB ArmyNavy Dr

(Hayes-Fern)

EB ArmyNavy Dr

(Hayes-Fern)

NB Hayes(AND-12th)

SB ArmyNavy Dr

(appr. 12th)

NB ArmyNavy Dr

(appr. 12th)

Sim

ula

tio

n S

pe

ed

(m

ph

)

Existing 2020 No-Build 2020 Build 2040 No-Build 2040 Build

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

NB Joyce St SB Joyce St WB ArmyNavy Dr

(Hayes-Fern)

EB ArmyNavy Dr

(Hayes-Fern)

NB Hayes(AND-12th)

SB ArmyNavy Dr

(appr. 12th)

NB ArmyNavy Dr

(appr. 12th)

Sim

ula

tio

n S

pe

ed

(m

ph

)


74

Future build scenario has significant operational impacts on the following intersections:

Army Navy Drive/S Hayes Street

Army Navy Drive/S Ferns Street

Army Navy Drive/S Eads Street

Army Navy Drive/12th Street

Table 12 Intersection Performances during AM Peak Hour

Intersection Existing (2015) 2020 No-Build 2020 Build 2040 No-Build 2040 Build

Delay LOS Delay LOS Delay LOS Delay LOS Delay LOS

Army Navy & Joyce 21.2 C 32.4 C 40.3 D 41.1 D 46.1 D

Army Navy & Parking Garage

24.0 C 39.2 D 50.2 D 60.7 E 56.1 E

Army Navy & Hayes 33.2 C 50.0 D 55.8 E 72.4 E 93.9 F

Army Navy & Fern 18.8 B 36.2 D 32.9 C 50.1 D 38.1 D

Army Navy & Eads 32.9 C 70.8 E 52.0 D 64.0 E 79.6 E

Army Navy & 12th 51.9 F 100.9 F 71.5 E 77.3 E 90.9 F

Joyce & North Driveway

19.6 C 8.2 A 7.1 A 8.5 A 7.9 A

12th & Hayes 30.6 C 16.9 B 8.9 A 16.9 B 9.9 A

12th & Fern 15.4 B 14.7 B 15.5 B 45.9 D 15.9 B

12th & Eads 12.0 B 26.7 C 12.6 B 31.0 C 15.6 B

Table 13 Intersection Performances during PM Peak Hour

Intersection Existing (2015) 2020 No-Build 2020 Build 2040 No-Build 2040 Build

Delay LOS Delay LOS Delay LOS Delay LOS Delay LOS

Army Navy & Joyce 24.7 C 19.5 B 35.3 D 19.9 B 42.6 D

Army Navy & Parking Garage

15.5 B 21.0 C 29.6 C 21.4 C 32.4 C

Army Navy & Hayes 26.2 C 45.7 D 38.1 D 49.6 D 62.8 E

Army Navy & Fern 23.2 C 54.8 D 47.9 D 60.2 E 79.6 E

Army Navy & Eads 42.1 D 113.7 F 93.2 F 115.5 F 138.0 F

Army Navy & 12th 11.4 B 93.7 F 121.3 F 251.8 F 240.3 F

Joyce & North Driveway

16.2 C 10.0 A 11.4 B 10.6 B 14.1 B

12th & Hayes 21.8 C 22.7 C 12.9 B 23.0 C 15.3 B

12th & Fern 17.4 B 25.4 C 25.0 C 33.9 C 33.6 C

12th & Eads 13.6 B 52.5 D 21.2 C 79.9 E 26.6 C

75

Figure 39 – Intersection Delay during AM Peak Hour

Figure 40 – Intersection Delay during PM Peak Hour

0.0

20.0

40.0

60.0

80.0

100.0

120.0

Army Navy &Joyce

Army Navy &Parking Garage

Army Navy &Hayes

Army Navy &Fern

Army Navy &Eads

Army Navy &12th

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(se

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0.0

50.0

100.0

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Army Navy &Joyce

Army Navy &Parking Garage

Army Navy &Hayes

Army Navy &Fern

Army Navy &Eads

Army Navy &12th

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76

Queuing

Prevailing traffic patterns show eastbound being the peak direction during the a.m. peak period, while

westbound is the peak direction during the p.m. peak hour. Two significant locations where this occurs

is the southbound leg of S Hayes Street/Army Navy Drive and the Army Navy Drive approaches at S Eads

Street.

Southbound S Hayes Street at Army Navy Drive

The intersection at S Hayes Street/Army Navy Drive is of particular importance because of its

connection to I-395 and Washington Boulevard, with the southbound approach serving as the freeway’s

off-ramps to Army Navy Drive. A priority goal for the Design Concept must include mitigating queues on

this approach as to not spillback onto the freeway. Examining the full queue storage available on the

approach is shown in Figure 41.

Figure 41 – Measured Southbound Queue Storage at S Hayes Street/Army Navy Drive

The shortest queue storage is from Washington Blvd at 1,970 feet. This storage distance serves as the

threshold no maximum queue may extend past to be considered acceptable. Furthermore, because the

maximum modeled queues will, in reality, be divided between the I-395 ramp and Washington Blvd

ramp, the maximum queue distance on either ramp will always be less than the maximum queue

reported.

Table 14 summarizes the maximum simulated queues for southbound movements at S Hayes

Street/Army Navy Drive. Results from all scenarios anticipate long southbound queues but are

accommodated within the existing off-ramp storage across all scenarios.

Table 14 Maximum simulated Queues at Southbound Hayes Street/Army Navy Drive Intersection

SB Hayes Approach Storage (ft) 95th-Percentile Queue (feet)

AM Adequate Storage? PM Adequate Storage?

2020 No-Build 1970 1000 YES 900 YES

2020 Build 1970 950 YES 425 YES

2040 No-Build 1970 1300 YES 1100 YES

2040 Build 1970 1675 YES 1000 YES

77


The geometric constraints of the Design Concept combined with heavy traffic demands at the S Eads

Street/Army Navy Drive intersection (during both a.m. and p.m. peak hours) are anticipated to produce

extensive queuing on all approaches. This queue spillback has been observed along Army Navy Drive in

both directions limiting throughput of neighboring intersections.

The eastbound approach currently produces queue spillback during existing conditions, a circumstance

anticipated to be mitigated in the Design Concept by including a dedicated left-turn lane. However,

other conflicting approach demands (particularly the heavy westbound through), and the need for

protected-only left-turn phasing also limit the ability to effectively process those volumes with single

lanes (493 eastbound left turns during 2020 p.m. peak hour versus 845 westbound thru-right turns).

Table 15 shows the maximum simulated queue results of eastbound left turn movement from no-build

and build models. The eastbound left-turn lane was modeled at the greatest possible length

(approximately 420-feet long) in the build models, which still cannot accommodate the heavy left-turn

demand. Queue spillback was observed in the build models during the peak periods and in the no-build

models during only the p.m. peak period.

Table 15 Maximum simulated Queues at Eastbound Eads Street/Army Navy Drive Intersection

EB Eads Approach Storage (ft) 95th-Percentile Queue

AM Adequate Storage? PM Adequate Storage?

2020 No-Build 540 700 NO 700 NO

2020 Build 420 300 YES 650 NO

2040 No-Build 540 700 NO 700 NO

2040 Build 420 650 NO 700 NO

It is anticipated that mitigating the queue spillback issue cannot be resolved through signal

timing/phasing changes, but requires additional lane capacity to process the volume demand.

SECTION 7

Summary of Findings

81

SUMMARY OF FINDINGS

While the purpose of the Design Concept is to promote and accommodate active transportation

(pedestrians and bicyclists) and transit use along Army Navy Drive, this study focuses on the automobile

and transit performance associated with the proposed improvements. Given the right-of-way

constraints along the Army Navy Drive corridor, trade-offs are inherent when accommodating multi-

modal needs. For corridors that undergo complete street improvements to provide pedestrian, bicycle,

and transit facilities, oftentimes traffic operations for vehicles degrade due to the reduction of travel

lanes and intersection capacity. The purpose of this study is to identify the level of impact to traffic

operations along the corridor and identify mitigation strategies to reduce impacts while

accommodating safety and the performance needs of non-auto users.

The operational analysis of existing, future no-build, and build traffic conditions identified several

intersections and movements that experience long queues, traffic congestion, and turning movements

that operate at Level of Service (LOS) E or F, which causes motorists at those movements to experience

high delays. Table 16 summarizes which intersections are anticipated to experience this by scenario.

82

Table 16 Intersections with Peak Hour LOS E or Worse by Scenario

Peak Hour Intersection 2015 Existing 2020 No-Build 2020 Build 2040 No-Build 2040 Build

AM


Army Navy & Pentagon Mall E E

Army Navy & Hayes E E F

Army Navy & Fern

Army Navy & Eads E E E

Army Navy & 12th F* F E E F

PM


Army Navy & Pentagon Mall

Army Navy & Hayes E

Army Navy & Fern E E

Army Navy & Eads F F F F

Army Navy & 12th * F F F F

*Indicates unsignalized intersection configuration

While individual intersection operations do not reflect the complete picture of how the system

performs under different Design Concepts, it helps identify the location of bottlenecks and “hot spots”

to warrant more-detailed investigation.


Positioned on the western end of the corridor, the intersection at S Joyce Street/Army Navy Drive is

anticipated to operate at LOS D or better under all scenarios. Notable findings include:

The eastbound approach experiences higher delays under the build scenarios notably due to

heavy left-turn movements limited by protected-only phasing.

The 2040 build scenario is exacerbated by heavier volume demands on all approaches,

particularly left-turns.


The intersection at Pentagon Mall Garage/Army Navy drive is expected to experience LOS E or worse

under both 2040 no-build and build scenarios during the weekday a.m. peak hour. Notable findings

include:

The westbound left-turn movement into the parking garage experiences the highest delay of all

movements at the intersection in all scenarios.

Reconfiguration of the parking garage exit in the build scenario is anticipated to accommodate

traffic demands without undue delay and queuing.

83


The intersection of S Hayes Street/Army Navy Drive is among the most critical along the corridor. It is

projected to operate at LOS E, or worse, under both build scenarios and 2040 no-build conditions

during the weekday a.m. peak hour. In all scenarios, the intersection’s connection to Interstate-395 (I-

395) and Washington Boulevard required queuing to be managed on the southbound approach to

prevent spillback onto the freeways. Notable findings include:

Northbound left turns experience high delays under both build and no-build conditions.

Southbound lefts experience high delays attributed to high demand.

Dual southbound left turn lanes were analyzed but have limited benefit due to queuing on the

downstream approach.

Results from the Vissim simulation analysis indicate that the maximum queue on the

southbound approach is not anticipated to spillback onto either I-395 or Washington Boulevard

under any future scenario analyzed.


The S Fern Street/Army Navy Drive intersection is mostly a point between the bottlenecks at S Hayes

Street and S Eads Street. The intersection is anticipated to operate at LOS E, or worse, only during the

2040 scenarios, mostly driven by queue spillback and heavy side street demands. Notable findings

include:

The northbound approach is anticipated to experience high delays in all future scenarios.

Eastbound delays at the intersection are mostly due to queue spillback from the S Eads



The intersection at S Eads Street/Army Navy Drive is a bottleneck along the corridor, given it is used to

access northbound I-395 and bus routes destined to the Pentagon. Both no-build and build lane

configurations have notable limitations in facilitating the traffic demand in future scenarios. Notable

findings include:

Eastbound left-turn queues consistently spill back through S Fern Street and S Hayes Street,

limiting throughput of the western intersections.

The heavy eastbound left-turn movement demand conflicts with a heavy westbound through

movement demand, thus competing for green time and causing delays to automobiles and

buses.

Northbound S Eads Street is constrained by a single approach lane given the relatively short

turn pockets.

The I-395 HOT lanes and associated improvements are expected to improve the operations at S

Eads Street and may relieve some of the anticipated congestion.

84


The intersection is currently unsignalized. Based on Arlington County plans, the intersection is planned

to be signalized in conjunction with the neighboring Clark Street/12th Street S intersection in the future.

The signalization will include the addition of median-running transit lanes as part of the 12th Street S

transit facility project. These improvements were assumed in the all future build and no-build

conditions. Notable findings from the analysis of this intersection include:

If unsignalized, the southbound movements are projected to experience significant queuing and

delay.

If signalized based on current plans, the following operational inefficiencies are anticipated: o Long clearance intervals due to the separation of the two intersections (12th Street and

Clark Street); o Limited flexibility to reallocate green time across phases due to the two-intersection

phasing. o The intersection (in conjunction with 12th Street S/Clark Street) has heavy turning

volumes compared to through volumes.

SCENARIO FINDINGS

Existing Conditions

General findings from the simulation analysis of existing conditions include:

Simulation results match with field observations of queues and driver behavior.

Simulation results at the intersection level are comparable to the Synchro analysis results.

Future No-Build Conditions Findings

General findings from the simulation analysis of no-build conditions include:

Significant congestion was observed in both future years during the weekday a.m. and p.m.

peak hours, notably at S Hayes Street, S Fern Street, S Eads Street and 12th Street

intersections.



The observed bottleneck is the eastbound approach at S Eads Street/Army Navy Drive. The

current eastbound lane configuration consists of a left-through and through-right layout,

which negatively impacts the progression of left-turn and through movements. The future-

year simulation analysis shows that demand is heavy on all legs with the predominant

conflicting movements being the eastbound left-turn movement and westbound through

movement. With heavy volumes destined to northbound I-395 and the limitation of a single

receiving lane, congestion is not expected to be alleviated by signal timing and phasing

improvements.

85

Future Build Conditions Findings

General findings from the simulation analysis of build conditions include:

Significant congestion was observed in both future years during both weekday a.m. and

p.m. peak hours, notably at S Hayes Street, S Fern Street, S Eads Street, and 12th Street S

intersections.

Queue storage on the southbound S Hayes Street approach (I-395 ramp) accommodates the

back of queue through 2040 for both weekday a.m. and p.m. peak hours.

Both build and no-build conditions show a major network bottleneck at the S Eads


o Similar to the no-build analysis the future-year simulation analysis indicates heavy

demand on all legs; the main conflicting movements are the eastbound left-turn

movement and westbound through movement. With heavy volumes destined to the

northbound direction towards I-395 and the limitation of a single receiving lane,

congestion is not expected to be alleviated by signal timing and phasing improvements.

o Queue storage for the eastbound left-turn is recommended to be extended as far as

possible, but block spacing remains a limiting factor. Even with maximum storage, left-

turn queue spillback is anticipated.

The overall Design Concept reduces vehicular capacity along Army Navy Drive by

reallocating right-of-way to non-auto users. However, as summarized in Table 16, all study

intersections anticipated to operate at LOS E, or worse, in 2040 will do so under both build

and no-build conditions, with the only exception being the intersection of Army Navy

Drive/S Hayes Street.

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RECOMMENDATIONS

The following section details the recommendations for the Design Concept, both geometric design and

signal operations, based on the traffic analysis completed.

GEOMETRIC RECOMMENDATIONS

The following section summarizes the geometric recommendations, shown graphically in Figures 45

through 50.

1. Joyce Street/Army Navy Drive

a. Northbound approach should be designed with a bike box configuration to

accommodate WB cyclists exiting the bicycle facility and continuing WB on Army Navy

Drive or turning right onto Joyce Street.

b. Westbound approach should be able to accommodate U-turns to provide access to the

Harris Teeter parking garage due to closing the existing median left-turn lane.

c. Southbound approach requires maintaining a left-turn lane with minimum storage

consistent with existing configuration.

Figure 42 – S Joyce Street/Army Navy Drive Recommendations Summary

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2. Parking Garage/Army Navy Drive

a. The northbound approach should be modified to a dedicated left-turn, dedicated

through, and dedicated right-turn lane configuration.

b. Pentagon Transit Center Considerations - Resolution with the ultimate design of the

Transit Center by the Pentagon must consider the west crosswalk as the latest designs

currently do not depict this pedestrian crossing. Include revised southbound approach

to shared left-through lane and dedicated right turn lane.

c. The westbound left-turn lane requires additional storage.

i. The current left-turn lane length shown in the Design Concept between Parking

Garage (on westbound Army Navy Drive) and Hayes Street (on eastbound Army

Navy Drive) should accommodate anticipated queues.

ii. Storage length of the westbound left-turn lane is as follows:

1. WB Army Navy Drive @ Parking Garage = 130-ft; 75-ft taper

Figure 43 – Pentagon Mall Garage/Army Navy Drive Recommendations Summary

89

3. Hayes Street/Army Navy Drive

a. The near-side bus stop along eastbound Army Navy Drive requires pedestrian

accommodations across the two-way bike lanes; consider similar treatment to mid-

block stop between Joyce Street and Parking Garage.

b. The northbound bike lane should be aligned along the curb rather than between the

through and right-turn lanes to prevent right-turning cyclists from conflicting with right-

turning vehicles. The model assumed that northbound left-turning cyclists would merge

into the vehicle lanes, but there are alternatives for accommodating left-turning cyclists.

A two-stage left-turn bike box could be installed or a bike signal/phase could be

considered. Although, an exclusive bike phase would result in a longer cycle length.

c. The southbound right-turn lane should have advanced signage of pedestrian crossing for

the channelized lane to encourage motorists to reduce speeds.

d. Dual southbound left-turn lanes have been considered but are not recommended. The

eastbound downstream through capacity limits any benefit of dual left-turn lanes.

e. Storage length of the left-turns lane are as follows:

iii. EB Army Navy Drive @ Hayes Street = 220-ft; 60-ft taper

iv. WB Army Navy Drive @ Hayes Street = 125-ft; 60-ft taper

Figure 44 – S Hayes Street/Army Navy Drive Recommendations Summary

90

4. Fern Street/Army Navy Drive

a. Consider access management alternatives, such as limiting ingress, regarding the

driveway on far-side of eastbound Army Navy Drive at Fern Street; potential right-out

only configuration to reduce conflicts with pedestrians and cyclists.

b. The northbound approach should be reconfigured as a designated left-turn lane,

through lane, and designated right-turn lane.

c. Storage length of the left-turns lane are as follows:

iii. EB Army Navy Drive @ Fern Street = 150-ft; 60-ft taper

iv. WB Army Navy Drive @ Fern Street = 50-ft; 60-ft taper

Figure 45 – S Fern Street/Army Navy Drive Recommendations Summary

91

5. Eads Street/Army Navy Drive

a. The eastbound left-turn lane requires the maximum storage possible within the block

due to heavy bus movements and traffic demands.

b. Consider revisions to the westbound approach to reduce conflict points; the design

should consider:

i. Restricting westbound traffic movements from US 110 (Jefferson Davis Highway)

from turning left onto Eads Street.

ii. Providing better accommodations at the existing pedestrian crossing on the US-

110 off-ramp. The County will conduct a marked crosswalk study in order to

determine what treatments are warranted for this location. The study will be

submitted to VDOT in a separate memorandum.

c. The northbound approach would benefit from elongating the two-lane cross-section

south to 11th Street S for additional capacity.

d. Storage length of the left-turns lane are as follows:

i. EB Army Navy Drive @ Eads Street = 420-ft; 60-ft taper

ii. WB Army Navy Drive @ Eads Street = 135-ft; 60-ft taper

Figure 46 – S Eads Street/Army Navy Drive Recommendations Summary

92

6. Army Navy Drive /12th Street S

a. Transit-only lanes between Army Navy Drive and 12th Street S should be converted to

general traffic lanes to improve traffic throughput.

i. Transit-only lanes between both intersections do not reduce bus delay with

recommended signal timing/phasing, which allows buses to use the segment

exclusively.

b. Prohibit westbound left turns due to sight distance concerns. Must provide westbound

U-turn movement at S Eads Street/12th Street S intersection to access garage.

Figure 47 – Army Navy Drive/12th Street S Recommendations Summary

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SIGNAL-RELATED RECOMMENDATIONS

A 130-second cycle length is recommended for 2020 weekday a.m. peak hour build scenario.

A 140-second cycle length is recommended for 2020 weekday a.m. peak hour and both 2040

weekday a.m. and p.m. peak hour scenarios.

Implement protected-only left-turn phasing along Army Navy Drive to reduce conflicts between

westbound left-turning vehicles, pedestrians, and bicyclists.

Eastbound/westbound bicycle movements along the bike facility will run concurrently with the

eastbound through phase.

Ensure all pedestrian intervals meet MUTCD recommended standards.

The Army Navy Drive/12th Street S intersection meets traffic signal warrants under Year 2020

and Year 2040 volume conditions and should be signalized. It is recommended that this

intersection run on the same controller as Clark Street/12th Street S and will be constructed as

part of the Crystal City Potomac Yard (CCPY) Transitway Extension project.

All analyzed signal timing parameters found in Appendix I.

SECTION 8

Recommendations

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REFERENCES

1. VDOT Functional Classification map: http://www.virginiadot.org/projects/fxn_class/maps.asp

2. Virginia Department of Transportation. Traffic Operations and Safety Analysis Manual. Version

1.0. November 2015.

3. Gorove/Slade. Traffic Impact Study and Transportation Demand Management – PenPlace Site.

Arlington County, Virginia. May 3, 2012.

4. Gorove/Slade. Traffic Impact Study and Transportation Management Plan – 400 Army Navy

Drive. Arlington County, Virginia. June 11, 2013.

http://www.virginiadot.org/projects/fxn_class/maps.asp

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