Aggressive Driving: Appendix 8

Excerpts from "A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility"

A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility
Institute of Transportation Engineers, 1997
Prepared by
Michael D. Meyer, Ph.D., P.E.
Georgia Institute of Technology

This document is the most comprehensive available listing and discussion of strategies for reducing congestion on highways. Congestion, with its attendant delay and queues, can be a prime source of driver frustration. Given the frustration-aggression model discussed in the guide, efforts to minimize congestion should be a prime means for eliminating significant triggers of aggressive driving in the traffic environment. The actions described in this document range from low-cost, short-term, to high-cost long-term.

Listed below are the sections in the document which apply to arterial streets. Following this are excerpts from some of the sections. The entire document may be purchased, or downloaded at no cost from: http://www.itsdocs.fhwa.dot.gov/\JPODOCS\REPTS_TE/8C301!.PDF

Arterials and Local Streets: Design

Super Street Arterials Intersection Improvements One-Way Streets Reversible Traffic Lanes Arterial Access Management Traffic Calming and Street Space Management

Arterials and Local Streets: Operations

Traffic Signal Improvements Computerized/interconnected Signal Systems Arterial Surveillance and Management Turn Prohibitions Improved Traffic Control Devices

Arterials and Local Streets System Management

High Occupancy Vehicle (HOV) Facilities on Arterials Parking Management Freight Movement Management Bicycle and Pedestrian Networks Enforcement

page 59 (Creating "Super Street Arterials)

Description: Super street arterials are wide, multi-laned arterials with limited access provided from intersecting streets. To the degree possible, major intersecting streets are grade-separated in order to minimize the need for traffic signals. Super streets take full advantage of as many traffic operations improvements as possible, including:

• traffic channelization
• grade separations
• street widening
• reversible traffic lanes
• intersection widening
• railroad grade separations
• left/right turn lanes
• improved traffic control devices
• two-way turn lanes
• removal of parking
• turn prohibitions
• lighting improvements
• one-way streets
• bus turnout bays

These measures generally provide spot or localized reductions in congestion.

p60

Intersections often can be designed or redesigned to improve the flow of vehicles and to assure the safe passage of pedestrians and bicycles. The use of traffic control devices such as stop and yield signs can provide significant improvements in capacity and safety.

p74

Traffic signal improvements generally provide the greatest payoff for reducing congestion on surface streets Traffic signal. Improvements include:

• Equipment update
• Timing Plan Improvements
• Interconnected Signals
• Traffic Signal Removal
• Traffic Signal Maintenance

pp 60-61

Implementation: In designing and improving arterial intersections that are at-grade, 11 principles have been established by the Institute of Transportation Engineers (ITE) that should be incorporated wherever possible (Institute of Transportation Engineers 1992; Neuman 1985) They are:

1. Reduce the number of conflict points among vehicular movements.
2. Control the relative speed of vehicles both entering/leaving an intersection.
3. Coordinate the type of traffic control devices used (such as stop signs or traffic signals) with the volume of traffic using an intersection.
4. Select the proper type of intersection to serve the volume of traffic being served. Low volumes can be served with no controls, whereas high levels of traffic may require more expensive and sophisticated treatments such as turning lanes or even at grade separation structures.
5. When traffic volumes are high, separate right turn and/or left turn lanes may be required.
6. Avoid multiple and compound merging and diverging maneuvers. Multiple merging or diverging requires complex driver decisions and creates additional conflicts.
7. Separate conflict points. Intersection hazards and delays are increased when intersection maneuver areas are too close together or when they overlap. These conflicts may be separated to provide drivers with sufficient time (and distance) between successive maneuvers.
8. Favor the heaviest and fastest flows. The heaviest and applicable fastest flows should be given preference in intersection design to minimize hazard and delay.
9. Reduce area of conflict. Large intersections cause driver confusion and inefficient operations. When intersections have excessive areas of conflict, us channelization.
10. Segregate nonhomogeneous flows. Separate lanes should be provided where there are volumes of traffic traveling at different speeds. For example, separate turning lanes should be provided for turning vehicles. Design for access by pedestrians and bicyclists. for example, when there are pedestrians crossing wide streets, refuge islands should be provided so that a large number of travel lanes have to be crossed at a time (see section on pedestrian and bicycle networks).

REFERENCES

Institute of Transportation Engineers. 1992 Traffic Engineering Handbook, Fourth Edition, Washington D.C.
Neuman, T. 1985. Intersection Channelization: Design Guide, NCHRP Report 279, Transportation Research Board, Washington D.C., November.

p65
Arterial Access Management

Description: In a general sense, access management is the control of the spacing, location, and design of driveways, medians/median openings, intersections, traffic signals, and freeway interchanges. Access management elements often include one or more of the following:

• physically restricting left turns
• restricting curb cuts and direct access driveways
• separating obvious conflict areas
• eliminating parking
• locating intersections at no less than minimum intervals
• constructing frontage roads to collect local business traffic and funneling it to nearby intersections

The importance of access management is seen in the following statistics. Fifty-two percent of all accidents in Colorado were access-related; 32 percent of all fatalities. In Oklahoma, 57 percent of the accidents are access-related; in Michigan 55 percent. Better managing arterial access could thus provide significant safety benefits to a community.

p74
Arterials and Local Streets: Operations

Trends in urban traffic management suggest that one of the most important tools in the congestion management toolbox will be improving system operations.

Traffic Signal improvements

Description: Of the approximate 240,000 urban signalized intersections in the United States, about 148,000 need upgrading of physical equipment and signal timing optimization, while another 30,000 are only in need of signal timing optimization (Federal Highway Administration 1987). Traffic signal improvements generally provide the greatest payoff for reducing congestion on surface streets. There are a number of relatively basic improvements that can and should be made to improve traffic flow on arterials. They include:

Equipment update-In this case, an inventory of existing traffic control devices should be made to determine if new, more modem equipment can replace them. This would allow for the planning of a more comprehensive set of strategies to improve traffic flow.
Timing Plan Improvements-This action would require a data collection effort in order to update the traffic signal timing to correspond to current traffic flows. Appropriate pre-timing of signals has been very successful in improving traffic flows.
Interconnected Signals-Specific improvements could include one or more of the following: interconnected pre-timed signals, traffic actuated signals, interconnected actively managed timing plans, and master controls.
Traffic Signal Removal-Many traffic signals are no longer justified in urban areas due to changes in traffic patterns. Many of these intersections can be better controlled by two-way stop control. For those situations where peak traffic flows necessitate continued signalized control, but off-peak traffic does not, conversion of control from full to flashing operation can provide significant reductions in delay and congestion during the offpeak times. Removing traffic signals can reduce vehicle delay and decrease unwarranted stops. However, experience has shown that removing an existing traffic signal will likely be opposed by many groups, especially nearby residents.
Traffic Signal Maintenance-Traffic signals are often installed with little attention given to the cost and procedures required for maintenance. This is a problem that has become particularly critical in recent years as more sophisticated traffic control devices are installed. Several categories of maintenance should be considered: . Preventive maintenance, to be performed at regular intervals in order to avoid unnecessary problems;

• Response maintenance, which includes quick response to emergency situations as well as trouble shooting; and
• Design modification, which deals with the need to monitor new equipment as well as signals placed in new locations in order to ensure safe and effective operation.

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(second strategy-possible separate illustration)

Arterial Surveillance and Management

Description: Arterial surveillance and management is very similar in concept to the freeway and integrated freeway/arterial management systems discussed earlier in this chapter. This action could include the following kinds of efforts: . Incident detection and follow-up action to remove incidents:

• Service patrols
• Roving tow vehicles at key sites
• Motorist information system, including radio announcements, citizen-band radios and cellular phones
• Incident teams
• Real time transit passenger information systems at bus stops, kiosks, and via telephone
• Intersection surveillance and monitoring, using:
  • Loop detectors
  • Interconnected signal systems
  • Video monitoring of key intersections
• Parking control and management on key arterials, with greater enforcement of parking regulations on designated through arterials
• Integration of freeway and arterial management programs…
• Traffic surveillance and metering

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Turn Prohibitions

Description: Conflicts between turning vehicles and pedestrians and between turning vehicles from opposing directions can cause congestion delay and safety problems at intersections and driveways. Prohibiting turns is a means of eliminating such conflicts and reducing congestion and accidents.

The most cited reasons for prohibiting turning movements are:

• reduction in accidents
• increased intersection efficiency
• reduced delay
• reduced conflicts
• improved traffic flow