JCE 4600Transportation Engineering

Traffic Control

Human FactorsPrimary Driving Tasks

NAVIGATION

CONTROL

GUIDANCE

What makes a Traffic Control Device Effective? Fulfill a need Command Attention Convey a Clear, Simple Meaning Command Respect of Road Users Give adequate time for a proper response

MUTCD; Section 1A.02

Design and Location of Traffic Control Devices

1. Timing: Provide information at a steady rate Spread out lower priority information

2. Primacy: Place sufficient target value on more urgent devices Example: Flashing light on warning sign

3. Expectancy: Drivers respond more correctly to expected situations Give advance notice of an unexpected situation

4. Redundancy: Provide critical information in more than one way Pavement markings supplement signs

Timing:What’s wrong with this picture?

Source: PTOE Refresher Course

Primacy:What’s wrong with this picture?

Camden County Courthouse

Primacy:What’s wrong with this picture?

Source: PTOE Refresher Course

Expectancy:What’s wrong with this picture?

Tipperary Hill in western Syracuse

Expectancy:What’s wrong with this picture?

Source: PTOE Refresher Course

Expectancy:What’s wrong with this picture?

Redundancy:What’s wrong with this picture?

Forest Park

Redundancy:What’s wrong with this picture?

Source: PTOE Refresher Course

Promotes Uniformity in Design and Application

Why do we need an MUTCD?

MUTCD DEFINITIONS 1A-13(Shall)

Standard—a statement of required, mandatory, or specifically prohibitive practice regarding a traffic control device.

The verb “shall” is typically used. Standard statements shall not be modified or

compromised based on engineering judgment or engineering study.

MUTCD DEFINITIONS (Should)

Guidance—a statement of recommended, but not mandatory, practice in typical situations, with deviations allowed if engineering judgment or engineering study indicates the deviation to be appropriate.

The verb “should” is typically used.

MUTCD DEFINITIONS (May)

Option—a statement of practice that is a permissive condition and carries no requirement or recommendation. Option statements sometime contain allowable modifications to a Standard or Guidance statement.

The verb “may” is typically used.

Color Code – how many colors do we use?Section 1A-12

Shape/Color

Sign Size

Typical Standards, Guidance, and Options

Destination Signs

General Service Signs

Typical Application

Placement

PAVEMENT MARKINGS

Work Zones

Advance Warning Area

Transition Area Activity Area Work Space Traffic Space Buffer Space

Termination Area

Design Criteria is Provided

Example Problem

What is the minimum merging taper length for a 12-foot lane with a design speed of 55 mph?

Traffic Signal Warrants

Warrant 5 – School Crossing

Warrant 6 – Coordinated Signal System

Warrant 7 – Crash Experience

Warrant 8 – Roadway Network

Warrant 9 – Grade Crossing

DESIGN ISSUES Turning Path Sight Distance Channelization Access Management Intersection Configurations Traffic calming

Turning Templates

Turning Path Issues

Results of Poor Turning Paths

Maryland Heights, Missouri

Results of Poor Turning Paths

Sight Distance

Route M in Jefferson County, Missouri

250 feet

Advanced Flashers

Forest Park Parkway, St. Louis

150 feet

Upper Bottom Road, St. Charles

9 Principles of Channelization Discourage or prohibit undesirable or wrong-way

movements Clearly define desirable vehicle paths Encourage desirable and safe vehicle speeds Separate points of conflict Traffic streams should cross at near-right angles and

merge at flat angles. Facilitate the movement of high priority traffic flows. Facilitate the traffic control scheme. Accommodate decelerating, slow, or stopped vehicles

outside higher-speed through traffic lanes. Provide safe refuge ( e.g., pedestrians and handicapped)

Near Eglin AFB Florida

Access Management

Source: http://www.accessmanagement.govIndiana

What is Access Management?

“Access Management is the process that provides access to land development while simultaneously preserving the flow of traffic on the surrounding road system in terms of safety, capacity, and speed.”

(Federal Highway Administration)

Access Management seeks to limit and consolidate access along major roadways, while promoting a supporting street system and unified access and circulation systems for development. The result is a roadway that functions safely and efficiently for its useful life, and a more attractive corridor.

(Transportation Research Board)

Why Implement Access Management?

Up to 50% crash reduction 23-45% capacity increase 40-60% delay reduction Better business

environment Improved quality of life Save tax dollars

Source: Michigan DOT

Camdenton

Access Management Tools

Access rights Intersection spacing Access management

standards/guidelines Driveway controls Turning restrictions Frontage/backage roads Shared/cross access Comprehensive planning Zoning ordinances Site plan development Permitting

Planning Example

Maryland Heights Howard Bend Levee District

25M ft2 planned development Regional park Comprehensive plan

6-lane expressway Parallel collector roadway Extensive Coordination:

Developers, Land Owners, Levee District, Existing Businesses, St. Louis County and MoDOT

Backage Roads Near US12/18 in Madison, WI

Intersection Configurations

New Jersey“Near Side” Jug Handle

New Jersey“Far Side” Jug Handle

New Jersey“Far Side” Jug Handle

Three/Quarter Access Intersection

Three/Quarter Access Intersection

Median U-turns

Median U-turns

Median U-turns

Advantages Reduced Crash Potential Increased Cross-street Capacity Easily Retrofitted Medium/Low Cost

Disadvantages Indirect Movements

Unfamiliar to Drivers Public Education

Mainline Weaving

New Designs

I-270 and Olive Boulevard, St. Louis

Continuous Flow Intersection

St. Louis CFIRoute 30 at Summit

Photo courtesy of MoDOT

DDI at I-270 and Dorsett Road

DDI at I-70 and 5th Street

DDI at I-70 and Mid Rivers Mall Drive

DDI at I-270 and Dorsett Road

Traffic Calming

Forest Park

Traffic Calming Tools Available

Vertical Deflections, Horizontal Shifts,and Roadway Narrowings are intended to reduce speed and enhance the street environment for non-motorists

Closures (diagonal diverters, half closures, full closures, and median barriers) are intended toreduce cut-through traffic by obstructing traffic movements.

Potential Impacts:• can impact parking and driveway access • reduces pedestrian crossing width and

increases visibility of pedestrian • speeds reduced on average by 4% for two-

lane chokers and 14% for one lane chokers • bicyclists prefer not to have the travelway

narrowed into path of motor vehiclesEmergency Response Issues: • preferred traffic calming device by many

emergency response agencies

Chokers and Neck Downs

Raised Intersections

Potential Impacts: • reduction in through movement speeds at

intersection • reduction in midblock speeds typically less

than 10% • access not effected• entire intersection more pedestrian-friendly • no data available on safety impactsEmergency Response Issues: • slows emergency vehicles to approximately 15

mph

Full and Partial Closures

Potential Impacts: • concern over effects on emergency

response, street network connectivity, and parallel local streets that carry diverted traffic

• may divert significant traffic volumes • no significant effect on vehicle speeds

beyond the full street closureEmergency Response Issues: • can be designed to allow emergency

vehicle access

Turn Restrictions and One Way Systems

Diverters

MUTCD Homework – Due next class1. Using the 2009 MUTCD, create a design to provide drivers with advanced warning about an isolated signal on rural 2-lane road with moderate ADT and 55 miles per hour posted speed limit. Specifically address:

What signage/markings should be used? (give the MUTCD “code” and show a picture). If you use any signs,

How large should they be? How far should they be placed upstream of the traffic signal? Where should it be mounted in relationship to the driving lanes?

Are there any other special considerations that should be taken into account Provide references (page numbers, table numbers, etc) for all of your work.

2. Provide a typical traffic control scheme for a Lane Closure on a Minor Street. Base your drawing on the MUTCD.

3. What special considerations should be taken into account when installing traffic calming measures such as partial closures and diverters?

4. Under what conditions are Diverging Diamond Interchanges best suited?

5. When used appropriately, list 5 reasons that roundabouts can improve intersection safety.