hcm guidance for alternative intersections
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HCM GUIDANCE FOR ALTERNATIVE INTERSECTIONS
Michael Armstrong, E.I.
2015 FSITE WINTER WORKSHOP:
INNOVATIVE INTERSECTION/INTERCHANGE DESIGN APPLICATIONS
HCM 2010 “Major Update”
Alternative Intersections & Interchanges procedures to
be included in NCHRP 03-115 “Production of a Major
Update to the 2010 Highway Capacity Manual”
Target publication date within 2015
Extensive discussions at 2015 TRB Annual Meeting last
month (January 11-15, 2015)
Project Overview
McTrans™ involved
with Task 5
Updates to
calculation engine
and user interface
in HCS 2010™
Streets under
development
FHWA-HRT-13-083
New HCM Content & Organization
Ch. 23 (formerly Ch. 22): Ramp Terminals & Alternative Intersections
Part A: Concepts
Part B: Interchanges (Diamond, Parclo, SPUI, DDI)
Part C: Alternative Intersections (MUT, RCUT, DLT)
Ch. 34: Interchange Ramp Terminals Supplemental
Example Problems (8 new examples added)
Operational Analysis for Interchange Type Selection
O-D and Turning Movements
New HCM Content & Organization
Ch. 30 (formerly Ch. 29): Roundabout Corridors
Urban Streets Supplemental material; similar procedure
Incorporates new inputs such as inscribed/central island
diameter, circulating speed, median type, etc.
Performance measures include segment FFS, running time,
roundabout influence area, mid-segment access point delay,
geometric delay, v/c ratio, facility travel time, travel speed, etc.
Level of Service based on Percent BFFS
Displaced Left Turn (DLT) Intersections
Overview of new procedures
Example: Partial DLT
Signalized Intersections procedure (formerly Ch. 18,
now Ch. 19) used for all three intersections to obtain
performance measures, including Control Delay
Urban Streets procedure (formerly Ch. 17, now Ch. 18)
used for both segments to obtain flow-profile analysis
and performance measures
Demand input: “overall” O-D three separate TMC’s
DLT Intersections
DLT Intersections
LOS based on Experienced Travel Time (ETT):
summation of Control Delay(s) for each O-D
𝐸𝑇𝑇𝑖 = 𝑑𝑖 𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
DLT Intersections
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
To overcome issue of allowing major street through-plus-right
and opposing protected-left movements in the same phase:
crossover signals must be offset so left turns theoretically
experience zero delay at main intersection (P = 1.00)
Suggested procedure for calculating offset time included
Treat displaced lefts as if they don’t exist at main intersection
DLT Intersections
Impossible to re-create
actual phasing scheme
DLT Intersections
WB CrossoverEB Crossover Main Intersection
Example: Partial DLT
An EB/WB major street that
intersects a NB/SB minor street
at an isolated location has high
left-turn demands and several
failing movements. Other
movements are near capacity
and there is concern about
future traffic growth. Would
this conventional intersection
function better as a DLT? Control = fully actuated
PHF = 0.92
Lost Time = 2.0 s
Ext. of Eff. Green = 2.0 s
RTOR = none
Parking = none
Buses = none
Bikes, Peds = none
680 75720
709700
81
60060 460
69
447545
Delay: 64.1 s/veh
LOS E
Example: Partial DLT
3rd Int
WB Crossover
1st Int.
EB Crossover
2nd Int.
Main Intersection
350’ 350’
EBT,
EBR
790
EBL
700WBT,
SBR,
NBL
1285
EBT
709
EBR
81
NBL
680
NBR
75
NBT
720
SBR
60
SBL
460
SBT
600
WBR
69
WBT
545WBL
447
WBT,
WBR
614
EBT,
NBR,
SBL
1244
Offset: 45 s Offset: 45 s
Example: Partial DLT
MovementO-D,
veh/h
Individual TMC's, veh/h Control Delay, s/veh ETT*
VolumeInt. 1 Int. 2 Int. 3 Int. 1 Int. 2 Int. 3
EBL 761 761 22.5 17,123
EBT 437 859 437 1,352 0.4 41.9 2.5 22,034
EBR 422 422 42.5 17,935
WBL 486 486 25.7 12,490
WBT 340 1,397 340 667 4.0 29.3 0.4 15,817
WBR 328 328 29.7 9,742
NBL 739 739 23.7 17,514
NBT 439 439 19.8 8,692
NBR 425 425 19.8 8,415
SBL 500 500 26.2 13,100
SBT 364 364 23.4 8,518
SBR 353 353 23.5 8,296
Intersection ETT, s/veh 𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗 28.5 s/veh (55% improvement, LOS E to C)
Procedure is essentially an “extension” of the existing
Signalized Intersections and Urban Streets HCM
procedures with a few minor additions
Best suited for facilitating comparison to existing
conventional intersections
Data collection at existing DLT intersections may be
problematic based on the new procedure’s O-D demand
input requirement
DLT Intersections Summary
U-Turn Intersections (MUT, RCUT)
Overview of new procedures
Example: MUT
Example: RCUT
MUT & RCUT Intersections
Same concept of converting “overall” O-D demands
to three separate TMC’s
Ch. 19 and Ch. 18 procedures again handle
performance measures for the three signalized
intersections and two segments, respectively
TWSC procedures (now Ch. 20) used for unsignalized
U-turns, facilitates “hybrid” analysis
MUT & RCUT Intersections
Type # Legs Main Intersection U-Turn Intersections
MUT Four Signalized Signalized
MUT Four Signalized Stop Signs
MUT Three Signalized Stop Signs
RCUT Four Signalized Signalized
RCUT* Four Stop Signs or Merges/Diverges Stop Signs or Merges/Diverges
RCUT Three Signalized Signalized
RCUT* Three Stop Signs or Merges/Diverges Stop Signs or Merges/Diverges
MUT & RCUT Intersections
*Check for optional
weaving analysis
(now Ch. 13) for
RCUT intersections
with merges
No weaving
analysis necessary
Weaving analysis
recommended
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
MUT & RCUT Intersections
U-turn saturation flow adjustment factor (fUT)
depends on median width
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
fLT = 0.95 (conventional intersections)
MUT & RCUT Intersections
Dt = distance from main intersection to U-turn
Df = distance from U-turn to main intersection
a = delay by acceleration/deceleration in movements with merges
𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓
1.47 ∗ 𝐹𝐹𝑆+ 𝑎 𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇
ETT includes “Extra Distance Travel Time” (EDTT) for
movements using U-turns:
MUT & RCUT Intersections
EDTT = (U-Turn) – (Direct LT)
MUT & RCUT Intersections
LOS criteria again depends on ETT – but only for each
O-D movement (rather than intersection as a whole)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”,
Draft Chapter 23
MUT Configuration
East U-TurnWest U-Turn Main Intersection
RCUT Configuration
East U-TurnWest U-Turn Main Intersection
Example: MUT
A 4-leg MUT with stop signs at its U-turn crossovers is located in a suburban area. The N/S
major street has two through lanes with shared right-turn lanes at the main intersection,
while the minor street has one through lane and one exclusive right-turn lane at each
approach. Both U-turn crossovers have a single lane.
Segments = 800’
Storage bays = 500’
PHF = 0.95
FFS = 50 mi/h
HV = 2%
Grades = none
Peds = 100/h
RTOR = restricted
Yellow = 4 sec
Red = 1 sec
Signal = actuated, un-
coordinated280 60
700
40070
200
120080 50
50
80300
Determine ETT and LOS for all 12 O-D movements.
Example: MUT
1st Int.
South U-Turn
3rd Int.
North U-Turn
2nd Int.
Main Intersection
SBL,
SBT,
SBR
1330
EBL,
SBL
120
NBL,
NBT,
NBR
1040
EBT
400
EBR, EBL
270
WBT
300
WBR, WBL
130WBL,
NBL
360
SBR,
NBL
360
SBT,
WBL
1330
NBR,
SBL
110
NBT,
EBL
1050
Example: MUT
1st Int.
South U-Turn
3rd Int.
North U-Turn
2nd Int.
Main Intersection
SBL,
SBT,
SBR
1400
EBL,
SBL
126
NBL,
NBT,
NBR
1090
EBT
421
EBR, EBL
284
WBT
316
WBR, WBL
137WBL,
NBL
379
SBR,
NBL
379
SBT,
WBL
1400
NBR,
SBL
116
NBT,
EBL
1110
Example: MUT
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇
𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓
1.47 ∗ 𝐹𝐹𝑆
=800 + 800
1.47 ∗ 50
= 21.8 𝑠/𝑣𝑒ℎ
Example: MUT
𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗 ~ 24.4𝑠
𝑣𝑒ℎ, 𝐿𝑂𝑆 𝐶
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
Example: RCUT
A 4-leg RCUT with merges at the U-turns has its major
street running E/W and is located in a rural area.
Segments = 2,000’
Storage bays = 300’
PHF = 0.92
FFS = 60 mi/h
HV = 0%
Grades = none
200 20090
800
120
220
50100 100
110
180
500
Determine ETT and LOS for all 12 O-D movements.
Example: RCUT
3rd Int.
East U-Turn1st Int.
West U-Turn
2nd Int. Main Intersection
EBL, EBT, EBR
1140
NBL, NBT
290
SBL, SBT
150
EBL
120
WBR
200
NBL, NBT, NBL
490
WBL, WBT, WBR
790
SBL, SBT, SBL
250
WBT
700
WBL
180
EBT
900
EBR
270
Example: RCUT
3rd Int.
East U-Turn1st Int.
West U-Turn
2nd Int. Main Intersection
EBL, EBT, EBR
1240
NBL, NBT
315
SBL, SBT
163
EBL
130
WBR
217
NBL, NBT, NBL
533
WBL, WBT, WBR
859
SBL, SBT, SBL
272
WBT
761
WBL
196
EBT
978
EBR
293
Example: RCUT
No weaving
analysis necessary
Weaving analysis
recommended
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
Major street
through vs. minor
street through/left:
(1240, 163)
(859, 315)
(978, 533)
(761, 272)
No weaving
analyses
necessary!
Example: RCUT
Merging maneuvers are assumed to incur zero delay and no
significant delay expected from potential weaving segments,
therefore the only movements experiencing any control delay
are major street left turns at the main intersection
Using TWSC procedures (Ch. 20):
EB Left at Int. 2
v/c = 0.18
95th %ile Queue = 16.5’
Control Delay = 11.2 s/veh
WB Left at Int. 2
v/c = 0.35
95th %ile Queue = 39.5’
Control Delay = 15.0 s/veh
Example: RCUT
𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓1.47 ∗ 𝐹𝐹𝑆
+ 𝑎
=2,000 + 2,000
1.47 ∗ 60+ 15
= 60.4 𝑠/𝑣𝑒ℎ
=2,000 + 2,000
1.47 ∗ 60+ 10
= 55.4 𝑠/𝑣𝑒ℎ
NBT and SBT
NBL and SBL
Example: RCUT
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major
Update”, Draft Chapter 23
Example: RCUTMovement 1st Int. 2nd Int. 3rd Int. EDTT Total LOS
EBL 0.0 11.2 - - 11.2 s/veh B
EBT 0.0 0.0 0.0 - 0.0 s/veh A
EBR 0.0 0.0 - - 0.0 s/veh A
WBL - 15.0 0.0 - 15.0 s/veh B
WBT 0.0 0.0 0.0 - 0.0 s/veh A
WBR - 0.0 0.0 - 0.0 s/veh A
NBL 0.0 0.0 0.0 55.4 55.4 s/veh E
NBT - 0.0 0.0 60.4 60.4 s/veh E
NBR - 0.0 0.0 - 0.0 s/veh A
SBL 0.0 0.0 0.0 55.4 55.4 s/veh E
SBT 0.0 0.0 - 60.4 60.4 s/veh E
SBR 0.0 0.0 - - 0.0 s/veh A
MUT & RCUT Intersections Summary
Plenty of variation in terms of configuration types
Does not produce performance measures for intersection
as a whole – only individual O-D movements
Data collection at existing MUT or RCUT intersections
nearly impossible based on procedure’s O-D input
requirement
Diverging Diamond Interchanges (DDI)
Overview of new procedures
Example: DDI with signal control
DDI/DCD Interchanges
Very similar to existing conventional diamond interchange
procedure (formerly Ch. 22)
Certain movements can be signal- or yield-controlled;
includes new gap-acceptance model
New external lane utilization factors based on internal
lane configuration
New additional lost time adjustments based on clear-zone
widths and location of conflict points
DDI/DCD Interchanges
New saturation flow adjustment factors
Field research showed that
saturation flows at actual DDI’s
were over-predicted by 8.7%
Therefore, fDDI = 0.913
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
DDI/DCD Interchanges
New Lost Time equations
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
DDI/DCD Interchanges
New procedure for capacity of yield-controlled movements (similar to TWSC)
Regime 1: Blocked by conflicting platoon when the conflicting signal has
just turned green, resulting in zero capacity for the turning movement
Regime 2: Gap acceptance in conflicting traffic after the initial platoon
has cleared, with gap acceptance controlled by critical gap, follow-up
time, and conflicting flow rate
Regime 3: No conflicting flow when the conflicting signal is red, resulting in
full capacity, controlled by follow-up time of the yield-controlled approach
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
DDI/DCD Interchanges
ETT now used to determine LOS for all interchange types
𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇 𝐸𝐷𝑇𝑇 =𝐷𝑡
1.47 ∗ 𝑣𝐷+ 𝑎
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23
Example: DDI (Signalized)
The interchange of an
arterial at a freeway is a
DDI with signals controlling
movements from the
freeway onto the arterial.
Movements onto the
freeway from the arterial
are free-flowing
Determine the delays,
ETT and LOS.
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
Example: DDI (Signalized)
Closely spaced intersections = none
Signals = pre-timed
RTOR = none
Travel path radii = 75’ RT, 150’ LT
HV = 5%
PHF = 0.95
Start-up lost time = 2 sec
Extension of effective green = 2 sec
Parking, buses, bicycles, peds = none
Cycle length = 70 sec
Arterial FFS = 35 mi/h
Operating speed = 25 mi/h
Source: NCHRP 3-115 “Production of the
2010 Highway Capacity Manual Major
Update”, Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway
Capacity Manual Major Update”, Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”,
Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”,
Draft Chapter 34
Example: DDI (Signalized)
Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 34
Questions?
Stay up to date with HCM 2010 Major Update:
http://sites.kittelson.com/HCQS/Announcements
Check for periodic HCS 2010™ updates:
http://mctrans.ce.ufl.edu/mct/
What’s Next?
FHWA task work order to incorporate freeway-arterial
interactions (unite interrupted and uninterrupted flow)
1. How does an oversaturated off-ramp affect
freeway operations?
2. How does an oversaturated on-ramp affect
interchange operations?
Recommended changes to procedures under
development – stay tuned
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