U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
In their meetings with the scanning team, the Swedish hosts discussed a number of intersection safety improvements. To avoid eliminating any potential safety improvements, the team chose to include some treatments that might be considered high-cost safety improvements in the following list:
Use 100-second-maximum cycle lengths to improve pedestrian, bicycle, and motorist compliance with the red phase.
Use a pocket transmitter to extend a signal's green time for school groups or other special users. This approach could be used to comply with Americans with Disabilities Act requirements without providing unnecessarily long pedestrian clearance intervals when they are not needed.
Provide audible pedestrian-crossing signals to reinforce visual signals and address the needs of the hearing impaired.
Adopt intersection design and operational concepts based on approach speeds. For example, all signalized intersections with an approach speed limit greater than 70 kilometers per hour should be provided with exclusive turn lanes and perhaps have protected-only phasing for left and right turns.
Implement the LHOVRA system at isolated high-speed intersections where safety problems have been demonstrated and signal synchronization is not a concern.
The German hosts presented several intersection safety improvements. To avoid eliminating any potential safety improvements, the team chose to identify the following safety improvements regardless of their costs:
Determine clearance intervals based on conflict points and approach speeds. Doing so can be incorporated into design or signal-timing modifications inexpensively.
Develop and implement multidisciplinary (enforcement, education, and engineering) traffic safety commissions to identify, study, and recommend improvements at high-accident locations. The success of these commissions requires adequate training and/or traffic safety background for members and a strong leadership committed to improving traffic safety.
Publicly identify high-accident intersections through distinctive signing (similar to the curve warning sign).
Consider prohibiting left turns at congested intersections and instead install signing to reroute traffic to make three right turns.
Install "please wait" signals at pedestrian crossings to indicate that the pedestrian button has been activated.
Complete detailed, well-documented phasing and timing plans to ensure that change intervals can accommodate vehicles approaching the intersection. Such plans would ensure that motorists could stop with a reasonable deceleration rate or proceed and clear potentially conflicting traffic safely.
Perform safety audits as part of regular design and evaluation of high-accident locations.
Install photo enforcement equipment at high-crash locations. The German approach is to reduce motorists' speed on intersection approaches to minimize the consequences of potential conflicts.
Enhance intersection pavement markings for bicycle and pedestrian crossings. (Members of the German delegation disagreed about the effectiveness of additional pavement markings. One school of thought says the most effective way to improve nonmotorized safety is to provide protected phasing for pedestrian and bicycle traffic.)
Develop speed-related (rather than traffic volume-related) warrants for exclusive left-turn lanes and protected phasing requirements.
Eliminate right turns on red, particularly when pedestrian crossings are present.
Install pedestrian fences, or staggered crossings, so that pedestrians must turn when crossing a street and face oncoming traffic.
The team identified a number of low-cost improvements the Dutch implement to make signalized intersections safer. Many are aimed at improving the safety of pedestrians and bicyclists, since walking and biking are such significant means of travel, particularly in urban areas. Low-cost safety improvements include the following:
Limit maximum cycle lengths to 90 to 120 seconds to minimize delay and maximize compliance. In the case of actuation and demand control, cycle lengths are substantially shorter. Shorter cycle lengths tend to reduce the level of red-light running of both motorized and nonmotorized traffic.
Consider the effects of placing signal heads on the near side of the intersection so crossroad drivers cannot anticipate the end of a conflicting phase and pedestrian walkways are kept clear.
Suggest protected left-turn phasing, which may be helpful when opposing vehicle approach speeds are in excess of 50 kilometers per hour.
Target traffic law enforcement and automated enforcement actions based on speed and red-light-running violations at high-accident locations. Dutch officials strongly emphasized the importance of a coordinated public awareness program in conjunction with an automated enforcement program.
Provide countdown clocks at pedestrian and bicycle crossings.
Consider the use of large signal back plates to increase visibility.
Provide dynamic, radar-controlled speed signs at high-speed intersections.
Provide speed tables on intersection approaches to control speed.
Consider using punitive signalization ("cut-off" signals) to reduce high speed. If a vehicle is detected traveling more than 10 miles per hour over the posted speed limit, the signal changes to red before the vehicle enters the dilemma zone.
Develop a multidisciplinary (enforcement, citizens, universities, etc.) task force to target high-accident locations and the driver behavior associated with severe intersection accidents.
To the extent possible, provide consistency in intersection design and operation to minimize driver confusion.
The team observed a number of low-cost safety improvements in the United Kingdom:
Use short cycle lengths to encourage driver and pedestrian compliance with signal controls.
Provide dilemma zone protection through appropriate detector placement and settings for speeds greater than 35 miles per hour.
Deploy PUFFIN and TOUCAN technologies where pedestrian and bicycle traffic is present.
Provide zigzag pavement markings at lane edges approaching pedestrian crossings.
Use the speed discrimination and extension (SDE) strategy on high-speed approaches to vary green extension and minimize vehicles caught in the dilemma zone.
Use speed and red-light-running cameras where accidents are related to such violations.
Use road safety audits at preliminary design, final design, implementation, and follow-up levels.
Install high-friction surfaces in the dilemma zone at high-speed intersections.
Install offset crosswalks with staggered crossings to force pedestrians to face oncoming traffic.