Final Project Evaluation
The Traffic Calming Program (TCP) undertook a speed bump project in the Spring of 1996 to address traffic problems identified by residents along SW 61st Drive, from Barnes Road to Canyon Ct., as part of the Westside Corridor Traffic Management Plan.
The goal of the project was to mitigate high speeds of drivers using SW 61st Drive as an alternative to principal routes.
Speed bumps enhance street safety and livability by reducing the 85th percentile speed of vehicles using SW 61st Drive closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are effective tools to reduce vehicle speed without reducing access.
SW 61st Drive serves a single family residence neighborhood in a rural-urban setting. Barnes Road, to the north, and Canyon Ct., at SW 61st Drive's south end, are Local Service streets. SW 61st Drive has neither side walks nor curbs. Additionally, horizontal and vertical curves limit sight distances. A large portion of the daily traffic on SW 61st Drive is believed to be cut-through traffic due to construction on Highway 26 and a lack of alternate east-west traffic corridors.
A local resident circulated a petition in favor of the project. Of the 16 households along the street, 12, or 75%, signed the petition requesting speed bump installation.
Four 14-foot speed bumps, at 850 to 900 foot spacing, were constructed along the 0.58 mile length of SW 61st Drive, Barnes to Canyon Ct., on June 8, 1996 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 29 and 34 mph, have been shifted into the range of 23 to 28 mph. The average 85th percentile vehicle speed before the project was 35.3 mph. Since bump construction the average 85th percentile speed is 28.6 mph and ranges from a low of 24.6 mph (near the bumps) to a high of 30 mph. Before installation of the speed bumps 83% of drivers exceeded the posted speed limit of 25 mph and 27% exceeded the limit by 10 mph or more. Since bump construction 70% of drivers exceed the posted speed limit but only 3% exceed the limit by 10 mph or more.
Traffic volumes measured before bump construction averaged 800 vehicles per day (vpd). After bump construction volumes average 780 vpd. This change is within the expected normal daily fluctuation of traffic volumes.
Traffic Calming on SW 61st Drive, Barnes Road to Canyon Ct. has successfully reduced the average 85th percentile speed closer to the posted speed, enhancing street safety and livability.