Traffic Calming Issues
When any new traffic management approach is introduced, issues, concerns, and questions are bound
to arise. Design decisions related to traffic can have far-reaching consequences. Lives, economic well-being, and urban livability are directly affected.
Professional engineers, planners, government, and the public all are aware of and sensitive to proposals
for changes in the traffic environment. Roadway congestion, air quality, traffic safety, street crimes,
and the high cost of new improvements are among the most-widely debated issues in America today. New design ideas are, and should be, subjected to rigorous testing and evaluation before being accepted as
part of the standard engineering and transportation planning tool kit. Traffic calming is not a panacea for
urban transportation woes, but it can have significant benefits in many situations.
In considering the application of traffic-calming techniques, what specific issues are likely to arise? The discussion on the following pages focuses on traffic-calming issues.
1. Traffic safety.
The Issue: Encouraging people to walk, play, and bicycle in and next to the streets is just asking for trouble. They will have a false sense of security and accidents will increase. They will develop bad habits that may increase their when they leave the neighborhood.
Comment: Traffic-calming measures have been implemented in many European cities. In the Netherlands and Germany, extensive research has been conducted to evaluate the safety and impact of traffic-calming techniques and devices.
2. Impact on traffic volumes, distribution, and operations.
The Issue: Traffic calming will never work on anything except very low-volume residential streets. It will substantially reduce the amount of traffic that a street can handle efficiently and this is counterproductive.
We need to move vehicles, not restrict them. Furthermore, if we slow traffic on one streets, the traffic will simply be diverted to another street. The net result will be increased congestion and more problems overall.
Comment: A 5-year German Federal Government evaluation of traffic calming and follow-up research
found:
• Little change in overall traffic volumes.
• Reduction in average vehicle speeds by almost 50 percent.
• Average increase in motorist trip time of only 33 seconds.
3. Lack of proven design standards.
The Issue: There are no uniform, accepted, and legally defensible standards to follow. If we want to try traffic calming, where can we get specific information about design?
Comment: Many U.S. cities are now developing and testing design guidelines for traffic-calming improvements. Although uniform, national standards have yet to evolve, valuable experience is being gained. The list of references in this blog provides a starting point for further exploration of
specific design approaches.
4. Liability.
The Issue: These traffic-calming ideas may be accepted in Europe, but they haven’t really been tried here. Are we opening the door to all kinds of legal problems if somebody crashes on a traffic circle or a speed table and sues us?
Comment: When considering the use of any new design approach, concerns about liability can be addressed somewhat through performance of “due diligence” on the part of the engineer, planner, or other professionals involved in the design. Research into the experiences of other U.S. cities, European standards, and evaluation studies should be thorough and followed up with a first-hand look if possible. Construction of a pilot project or other testing of proposed designs can benefit, as can ongoing and systematic valuation of the improvements once installed.
5. Emergency and service vehicle access.
The Issue: Construction of speed bumps, neckdowns, medians, and traffic circles will increase response times for emergency vehicles and may restrict access for garbage trucks, delivery vans, and other large vehicles.
Comment: Studies in Berkley and Palo Alto, CA, show that traffic management measures (e.g., traffic diverters, bicycle boulevards) have not impaired police or fire emergency response times. • The Seattle Engineering Department works closely with its Fire Department to design and field-test traffic circles on a site-specific basis to ensure good emergency access.
6. Impacts on bicycling.
The Issue: Pavement texturing, speed tables, wider sidewalks, “bulb-outs” at corners and similar
improvements may make things better for pedestrians, but may have a negative impact on bicycling.
Emergency vehicle access should always be considered when incorporating traffic-calming
measures.
Comment: A 5-year German Federal Government evaluation of traffic calming and follow-up research found doubling of bicycle use over a 4-year period.
• Implementation of traffic management strategies in the downtownarea of the Dutch City of Groningen contributed to a substantial increase in bicycling and walking. Bicycle use is now well over 50 percent of all trips.
• Studies of traffic-calming areas in Japan show increases in both bicycle and pedestrian traffic volumes along most routes.