The Traffic Calming Program (TCP) undertook a speed bump project in the Fall of 1993 to address traffic problems identified along SW Hamilton Street between Dosch Road and Shattuck Road as part of the Westside Corridor Traffic Management Plan.
The goal of the project was to mitigate high speeds from expected use of Hamilton 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 Hamilton closer to the legal maximum speed limit of 30 miles per hour (mph). Speed bumps have proven to be effective tools to reduce vehicle speed without limiting access, though volume reductions are typical.
SW Hamilton, a Neighborhood Collector, provides access to several single family residence neighborhoods in a rural urban setting. Dosch Road, to the east, and Shattuck Road, to the west, are both Neighborhood Collectors. SW Hamilton has neither sidewalks or curbs, and is a designated transit and primary fire response route. Additionally, there are vertical curves which limit sight distances, and a 20 mph school zone and school cross walk within the project limits. A significant portion of the daily traffic on SW Hamilton is believed to be cut-through traffic.
A petition for residents along SW Hamilton to sign was circulated by a local resident. Of the 62 households along the street, 49, or 79%, signed the petition requesting speed bump installation.
Six 22-foot speed bumps, at 470 to 870 foot spacing, were constructed along the 0.9 mile stretch of SW Hamilton in November of 1993 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 35 and 40 mph, have been shifted into the range of 26 to 34 mph. The 85th percentile vehicle speed before the project was 43 mph. After bump construction the average 85th percentile speed was 33 mph and ranged from a low of 31 mph (near the bumps) to a high of 38 mph.
Traffic volumes measured before bump construction were 2600-3300 vehicles per day (vpd). After bump construction volumes measured 2000-2700 vpd. Volumes tend to increase near Shattuck
A summary of reported accidents is presented in Table 1, below.
Table 1. Accident Review
Dosch Rd to W/Shattuck
|Total Accidents||Property Damage Only||Injury
|24 Months Before Project||6||5||1||3|
|24 Months After Project||5||3||2||3|
Traffic Calming on SW Hamilton has successfully reduced the 85th percentile closer to the posted speed, reduced traffic volumes and enhanced street livability.