Speed Cushions Slow Cars, Not Emergency Vehicles

In early November, the Ada County Highway District installed speed cushions to slow traffic on Bison St. in Boise, ID. The devices were installed in response to resident complaints of speeding vehicles. While the first request for traffic calming was denied, the residents appealed the decision and the district's commissioners unanimously approved the appeal.

When a new development was built on the ridge above Bison, the formerly quiet neighborhood street became a through street for new residents. At least one incident was formally reported of a driver unable to make a turn due to excessive speed, who instead drove over the sidewalk and onto someone's property. Several similar episodes were reported anecdotally.

The average speed of vehicles was 28 mph with some cars going as fast as 40 mph on this quiet community street. The goal was to slow vehicles to a more reasonable 22-26 mph.

Traffic Logix rubber speed cushions were selected for this project. Since Bison is used by emergency vehicles headed to the above development, it was imperative that the devices not slow response time. While speed humps cause all vehicles to slow down, speed cushions are constructed as several small humps with spaces between them. Cushions force cars to slow down while riding over them, while the wider wheel base on EMT vehicles can straddle the middle cushion without slowing down.

The Boise Fire Department approved the Traffic Logix rubber speed cushions for use due to their compatibility with primary response vehicles. While humps slow response time to 6-7 minutes, the cushions allow emergency vehicles to obtain a more typical response of 4-5 minutes.

The rubber cushions are prefabricated since cushions can be difficult to create and maintain with asphalt. The simple installation process ensures that products can be easily moved and relocated. This is particularly advantageous on Bison since the city plans to eventually turn the street into a cul-de-sac and will then reinstall the devices on other local streets.

The city intends to use additional Traffic Logix products as the need arises. When complaints are received from residents and a traffic study verifies the need for traffic calming, the products will be used on minor collectors or on streets where response time is a concern. The Boise Fire Department has been pleased with the speed cushions and may be interested in having them installed along additional fire routes in the future.

While a formal traffic study will not be conducted until the Spring, Assistant Traffic Engineer John Wasson reports that residents are happy with the products and the resulting 15-18% reduction in vehicle speed.

The two local commissioners, President John Franden and Commissioner Rebecca Arnold, who were inundated with complaints regarding Bison Street, are quite satisfied as well. As Mr. Wasson reported, in place of complaints, the commissioners are now receiving thank yous.

To find out more about the Boise, ID traffic calming program, contact: John Wasson jwasson@achd.ada.id.us .