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.

The most fundamental traffic-calming goal is to reduce the speed of vehicular traffic . With the reduction of speed, the following important objectives can be realized:

1. Improved “feel” of the street.

This objective calls for increased community involvement in and “ownership” of the street. If people feel more comfortable on the street, they are more likely to walk or bicycle there and to engage in other street oriented activities with their neighbors. A key aspect of achieving this objective is reducing the perceived threat of danger from motor traffic.

2. Enhanced aesthetic values and a sense of nature.

Several traffic-calming techniques, such as street landscaping, pedestrian amenities, and reclamation of roadway areas can serve as community open space.  Not only do these techniques make the neighborhood more attractive, but they also break up long, uninterrupted street vistas conducive to speeding and convey the message that “this is a pedestrian place.”

3. Reduced crime.

It’s harder to make a speedy getaway if a fleeing felon has to deal with speed humps, woonerfs, and traffic circles. It’s harder to get away without being spotted if there are “eyes on the street” – if the street is a positive, community focus.

4. Equitable balance among transportation modes.

With reduced motorist speeds, safety is improved. Pedestrians and bicyclists have more time to detect and avoid motor vehicles. Traffic calming sends the message that “motor vehicles don’t exclusively
OWN the roadway” – that other modes have equal rights. Studies that evaluate traffic-calming improvements show increased levels of walking, bicycling, and transit use following installation.

5. Increased safety/decreased severity of injury in traffic crashes.

With reduced speeds comes a significant reduction in the number and severity of crashes involving motor vehicles. Traffic-calming facility evaluations uniformly show fewer crashes, fewer fatalities, and less severe injuries.

6. Improved air quality and noise levels.

Slower moving vehicles make less noise and, generally, emit fewer pollutants.

7. Decreased fuel consumption.

With more trips made by walking, bicycling, and transit, and with slower traffic speeds, fuel consumption reductions of 10 to 12 percent have been reported.

8. Continued accommodation of motor vehicle traffic.

An important objective is the continued accommodation of motor vehicle traffic. Although traffic calming shifts the balance among travel modes, this shift should not result in severely restricted traffic volumes or in shifting traffic problems from the traffic-calmed area to other streets.

This list of six traffic calming objectives comes from the U.S. Department Of Transportation Federal Highway Administration Website.

Six Main Objectives of Traffic Calming

1. To encourage public involvement in the traffic calming process by incorporating the preferences & requirements of the citizens,
2. To reduce vehicular speeds,
3. To promote safe & pleasant conditions for motorists, bicyclists, pedestrians, & residents,
4. To improve the environment & livability of neighborhood streets
5. To improve real & perceived safety for non-motorized users of the streets,
6. To discourage use of residential streets by non-citizens cut through vehicular traffic.

Sounds good in theory but how does all this work practically.  Please provide your comments and experiences.

Traffic Calming? What is it?

According to our friends at the Instutute of Transportation Engineers:

Traffic Calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior and improve conditions for non-motorized street users.¹

Traffic calming goals include:

• increasing the quality of life;
• incorporating the preferences and requirements of the people using the area (e.g., working, playing, residing) along the street(s), or at intersection(s);
• creating safe and attractive streets;
• helping to reduce the negative effects of motor vehicles on the environment (e.g., pollution, sprawl); and
• promoting pedestrian, cycle and transit use.¹

Traffic calming objectives include:

• achieving slow speeds for motor vehicles,
• reducing collision frequency and severity,
• increasing the safety and the perception of safety for non-motorized users of the street(s),
• reducing the need for police enforcement,
• enhancing the street environment (e.g., street scaping),
• encouraging water infiltration into the ground,
• increasing access for all modes of transportation, and
• reducing cut-through motor vehicle traffic.

¹Lockwood, Ian. ITE Traffic Calming Definition. ITE Journal, July 1997, pg. 22.

This excellent article just about says it all.  It not only defines what traffic calming is it also provdes the objectives and goals of traffic calming devices.

As I am sure you can tell from this excerpt, the ITE traffic calming website is an excellent resource to use when you need information about speed bumps, speed humps, speed tables or any other type of traffic calming device.  So check it out!