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 Shattuck Road and Scholl's Ferry 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 impacting access, though volume reductions are typical.
SW Hamilton, a Neighborhood Collector, provides access to several single family residence neighborhoods in a rural urban setting. Shattuck Road, to the east, is a Neighborhood Collector and Scholl's Ferry Road, at the west end, is a Major City street. 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. 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 47 households along the street, 32, or 68%, signed the petition requesting speed bump installation.
Five 22-foot speed bumps, at 450 to 1100 foot spacing, were constructed along the 0.75 mile stretch of SW Hamilton in May of 1994 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 34 and 37 mph, have been shifted toward 31 mph. The 85th percentile vehicle speed before the project was 40 mph. After bump construction the average 85th percentile speed was 34 mph and ranged from a low of 33 mph (near the bumps) to a high of 36 mph.
Traffic volumes measured before bump construction were 3500 vehicles per day (vpd). After bump construction volumes averaged 2600 vpd.
An analysis of reported accidents is presented in Table 1, below.
Table 1. Accident Review
Shattuck Rd to
Scholl's Ferry Rd
|Total Accidents||Property Damage Only||Injury
|12 Months Before Project||2||1||1||1|
|12 Months After Project||1||1||0||0|
Traffic Calming on SW Hamilton has reduced the 85th percentile closer to the posted speed, reduced traffic volumes, and enhanced street livability.