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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.