The Traffic Calming Program (TCP) undertook a speed bump project in the Spring of 1994 to address traffic problems identified on SW Shattuck Road between Hamilton Street and Patton Road as part of the Westside Corridor Traffic Management Plan.
The goal of the project was to mitigate high speeds from expected use of Shattuck Road as an alternative to principal routes due to congestion caused by light rail construction on Highway 26. Speed bumps enhance street safety and livability by reducing the 85th percentile speed of vehicles using SW Shattuck closer to the legal maximum speed limit of 35 miles per hour (mph). Speed bumps have proven to be effective tools to reduce vehicle speed without impacting access, though volume reductions are typical.
SW Shattuck, a Neighborhood Collector, serves as access to several single family residence neighborhoods in a rural urban setting. Patton Road, to the north, and Hamilton Street, to the south, are also Neighborhood Collectors. SW Shattuck is located in an area of many hills and it's grade varies from 3-10 percent. SW Shattuck has neither curbs or sidewalks, and is a designated transit and primary fire response route. A significant portion of the daily traffic on SW Shattuck is believed to be cut-through traffic.
A petition for residents along SW Hamilton to sign was circulated by a local resident. Of the 25 households along the street, 17, or 68%, signed the petition requesting speed bump installation.
Three 22-foot speed bumps, at 330 to 370 foot spacing, were constructed along the 0.5 mile stretch of SW Shattuck, where street grades allowed, in June of 1994 by the Bureau of Maintenance.
As the graph shows, vehicle speeds previously ranged between 35 and 41 mph. Since speed bump construction, speeds have been shifted into the range of 29 to 35 mph. The average 85th percentile vehicle speed before the project was 42 mph. After bump construction the average 85th percentile speed was 33 mph with a low of 32 mph to a high of 35 mph. Speeds were typically higher in the southbound (downhill) direction.
Traffic volumes measured 3200 vehicles per day (vpd) before bump construction. Traffic volumes averaged 3400 vpd after bump construction.
An analysis of reported accidents is presented in Table 1, below.
Table 1. Accident Review
Hamilton St to Patton Rd
|Total Accidents||Property Damage Only||Injury
|18 Months Before Project||1||0||1||1|
|18 Months After Project||1||0||1||1|
Traffic Calming on SW Shattuck has successfully reduced the 85th percentile closer to the posted speed and enhancing street safety and livability.