Liability
Community groups and others seeking traffic calming for their neighborhoods often hear that legal liability-both for individual engineers and the City-is a big problem. This is simply not true. No NYCDOT engineer has ever been held personally liable for damages arising from traffic calming, and in the four years that NYC has had speed humps, the City has only paid one liability claim, for a broken muffler, because a warning sign was mistakenly installed after a speed hump. Nationwide, thousands of speed humps and traffic calming devices have been installed since the 1970s, with only six liability verdicts. Compared to the steady stream of liability cases that cities face from simple road maintenance and construction, speed humps and traffic calming devices-have minimal liability risk.

Noise
Another concern that residents often express about traffic calming-and especially speed humps-is an increase in noise in the area. However, experience has shown that the lower speeds resulting from traffic calming actually decrease noise. As reported in Traffic Calming: State of the Practice by the Institute of Transportation Engineers, Charlotte NC, San Jose CA, and Boulder CO all performed extensive tests before and after the installation of speed humps, and in each case, found that noise levels had actually dropped. NYC DOT's own speed hump before/after noise tests in the mid-90s showed reduced noise as well.

Air Quality
Opponents of traffic calming assert that traffic calming devices increase local air pollution by decreasing the efficiency of traffic flow. This has never been proven true, and ignores the established fact that traffic calming encourages non-polluting cycling and walking and reduced car trips, thereby decreasing automotive pollution.