Monday, April 30, 2007

Traffic calming

Traffic reassuring is a set of strategies used by urban planners and traffic engineers which aims to slow down traffic and improve safety for pedestrians and bicyclists, although some of these features can also be dangerous to cyclists. It is now relatively common in Europe, especially Northern Europe; less so in North America.
Traffic calming has traditionally been justified on the grounds of pedestrian security and reduction of noise and local air pollution which are side effects of the traffic. However, it has become increasingly apparent that streets have many social and recreational functions which are severely impaired by fast car traffic. For example, residents of streets with light traffic had, on average, three more friends and twice as many acquaintances as the people on streets with heavy traffic which were otherwise similar in dimensions, income, etc. For much of the twentieth century, streets were designed by engineers who were charged only with ensuring traffic flow and not with fostering the other functions of streets. The rationale for traffic calming is now broadening to include designing for these functions.
Displaced traffic is not fully pushed onto other routes, as some travelers may begin to walk or use other modes such as public transit and bicycles to get where they are going. Still, in most cases the affected motorists have few alternatives aside from either navigating the newly erected obstacles or finding a more palatable route. This happens because high traffic tends to be generated by motorists passing through the area and not by the local residents.

It should be noted the some of these measures have a tendency to irritate and annoy drivers rather than calm them and others can actually increase traffic throughput. Some drivers who slow down at calming points, however, accelerate and speed after passing them in order to "catch up for lost time". For this reason, more advanced methods integrated into the design of the street, which make slower speeds seem more natural to drivers and less of an artificial imposition, are now preferred - the goal is to slow down the driver through psychological, at least partly subconscious means instead of simply forcing him to do so.

One major side effect of traffic reassuring is the impedance to emergency services. A police car can easily navigate most traffic reassuring measures. The same cannot be said for fire trucks and ambulances, however. They often have to slow down to safely cross speed bumps or chicanes. In some locales, the law prohibits traffic calming measures along the routes used by the urgent situation services.
There are 3 "E"'s that traffic engineers refer to when discussing traffic reassuring: engineering, education, and enforcement. Because neighborhood traffic management studies have shown that often it is the residents themselves that are largely contributing to the perceived speeding problem within the neighborhood, it is strained that the most effective traffic calming plans will entail all three components, and that engineering measures alone will not produce satisfactory results.

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