The Bureau of Transportation System Management undertook a Residential Speed Bump Purchase Project in the fall of 1998 to address traffic problems identified by residents along SE 71st Avenue from Division Street to Powell Boulevard. The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using 71st Avenue closer to the legal maximum speed limit of 30 miles per hour (mph).   It is not an intended goal to reduce traffic volume Collector Streets.

 

This section of 71st Avenue is in a single family residence neighborhood. To the north, Division Street is a Neighborhood Collector street. At 71st Avenue's south end, Powell Boulevard is a Major City Traffic street. There are sidewalks and curbs on this portion of 71st Avenue.

 

Residents along 71st Avenue were invited to an open house on October 21, 1998, to review and comment on the proposed speed bump installation. Most of the 25 people who attended expressed approval for the proposed project. A petition was available at the open house for residents along 71st Avenue to sign, and was circulated after the open house by a local resident. Petition results were as follows:

 

Vote	Amount	Percent of Total
Yes	43	67.19%
No	0	0%
No Signature	21	32.81%
Total	64	100%

 

On July 31,1999, the Bureau of Maintenance constructed six 22-foot speed bumps, at 400- to 450-foot spacing, along the 0.54 mile length of 71st Avenue from Division Street to Powell Boulevard.

 

As the graph shows, vehicle speeds that previously peaked between 26 to 28 mph, now peak between 20 to 22 mph. The average 85th percentile vehicle speed before the project was 30 mph. Since bump construction, the average 85th percentile speed is 25 mph. Before installation of the speed bumps, 15 percent of drivers exceeded the posted 30-mph speed limit, and 0.1 percent exceeded the limit by 10 mph or more. Since bump construction 2.3 percent of drivers exceed the posted speed limit and 0.1 percent exceed the limit by 10 mph or more.

 

Traffic volumes measured before bump construction averaged 3,204 vehicles per day (vpd). After the speed bumps were installed, volumes averaged 2,982 vpd.

 

Traffic calming on SE 71st Avenue from Division Street to Powell Boulevard has successfully reduced the average 85th percentile speed closer to the posted speed, enhancing street safety and livability.