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Traffic Calming Program: Physical Traffic Calming Devices

The following physical traffic calming devices, traffic circles, chicanes, and speed humps, are installed on non-arterial streets that are also non-emergency routes.  The appropriate device depends on the roadway geometry, sight distance, and the traffic characteristics such as speed and volume.

Traffic Circles - Used primarily to reduce collisions at intersections, traffic circles can also reduce speeding along residential street corridors and improve bicycle and pedestrian safety.  In addition to these safety benefits, many circles can be landscaped, which can provide aesthetic enhancements to the street.

ChicaneChicanes – A series of 2 or 3 curb bulbs, chicanes slow traffic by creating a narrow, winding section of roadway.  Like traffic circles, many chicanes can be attractively landscaped.  Since they result in eliminating some parking, they are generally only installed where there is low demand for on-street parking.

Speed humpSpeed Humps – 12’ long, 3” high mounds that extend the full width of the street, speed humps can be effective at reducing speeds. They are generally only used when speeds are very high as they can divert traffic to adjacent streets.


The following physical traffic calming measures, speed cushions, radar speed signs, and road rechannelizations are installed on arterial streets and non-arterial emergency routes.

Speed cushionSpeed Cushions –  Similar to speed humps, speed cushions  are divided into sections so that wide wheelbase vehicles can straddle them.  As such, they can more easily accommodate transit, fire engines, and other emergency response vehicles.

Radar speed signRadar Speed Signs – By displaying the speed of oncoming vehicles, these signs provide direct feedback to drivers and remind them to slow down.  This can also be an effective device for multi-lane arterial streets.

Road Rechannelization – Sometimes referred to as “road diets”, a typical rechannelization project reconfigures the street from four multi-purpose lanes to two multi-purpose lanes, a center left turn lane, and bicycle lanes. This lane combination can decrease vehicle collisions, reduce vehicle speeds and improve pedestrian and bicycle safety.

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