Traffic Calming Defined:
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.

Traffic Calming Sum: Oregon Department of Transportation Bicycle and Pedestrian Plan

"Citizens are often concerned about excessive traffic volumes and speeds on residential streets. Local streets are intended to serve the adjacent land use at slow speeds, yet they are often designed so that high speed travel is accommodated. Well-designed traffic calming devices effectively reduce traffic speeds and volumes while maintaining local access to neighborhoods.

Motorists often choose short-cuts through residential areas when the arterial or collector street system isn't functioning properly. Traffic calming should be viewed as an area-wide treatment, rather than a solution for only one or two problem streets, so that through traffic is not diverted onto other residential streets; this may require improving the arterial street system.

Public involvement is needed for residents, businesses, planners and engineers to understand the issues and agree with the proposed changes.

The benefits of traffic calming for bicycling and walking are:

• Reduced traffic speeds and volumes allow bicyclists to share the road with vehicles;
• Quieter streets and increased ease of crossing enhance the pedestrian environment;
• Lower traffic speeds increase safety (high speeds are responsible for many pedestrian fatalities); and
• Parents will be more likely to let their children walk or ride a bike in the neighborhood if the streets are made safer.

Some earlier attempts at traffic calming in this country have not proven effective for several reasons:

• The technique slowed cars down excessively, encouraging drivers to accelerate to higher speeds to make up for lost time, which increases noise and air pollution. For example, speed bumps are uncomfortable to cross at even very low speeds, and are unpopular with bicyclists.
• The technique was a misuse of traffic controls, breeding disrespect for their legitimate use; e.g. four-way stop signs are often ignored where there is no perceived danger.
• No further efforts were made beyond placing speed limit signs. Most drivers travel at a speed they feel comfortable with, which is usually a product of roadway design.

Effective traffic calming techniques rely on these general principles:

• The street design allows drivers to drive at, but no more than, the desired speed;
• The street design allows local access, while discouraging through traffic; and
• Traffic calming works best when roads are properly designed in the first place.

Traffic calming can be viewed as a method to help reestablish the proper hierarchy for streets:

• Local streets should carry local traffic at slow-speeds, with bicyclists sharing the road and pedestrians crossing freely.
• Collector streets should carry traffic to and from local streets and arterials, at moderate speeds. Bicyclists should be able to share the road or ride on bike lanes. Pedestrians should be provided with buffered sidewalks and frequent crossing opportunities.
• Arterial streets should carry mostly through traffic. Bicyclists should be accommodated with bike lanes. Pedestrians should have buffered sidewalks and be offered reasonably-spaced crossing opportunities." See the Oregon site for more information

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