The Traffic Calming Program (TCP) undertook a project in the Winter of 1994/95 to address traffic problems identified by residents along SE 58th Avenue between Division Street and Powell Boulevard.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using SE 58th closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only device considered for streets like SE 58th, which are classified as Local Service Streets, are not transit or primary fire response routes and have vehicle volumes between 400 and 1700 vehicles per day. Speed bumps have proven to be effective tools to reduce vehicle speed without impacting access. It is not an intended goal to reduce traffic volume on low-volume Local Service Streets.
SE 58th Avenue serves a mixed single family residence and apartment neighborhood. Division Street, to the North, is a Neighborhood Collector. Powell Boulevard, at SE 58th's South end, is a Major City Traffic Street. SE 58th has sidewalks and curbs. There are vertical curves which limit sight distances. A significant percent of the daily traffic on SE 58th is believed to be cut-through traffic due to SE 58th's proximity to Franklin High School and Atkinson Elementary School.
All residents along SE 58th were invited to an open house April 4, 1995 to review and comment on the proposed speed bump installation. Eighteen households were represented at the open house. The majority of those who attended expressed approval for the proposed project. A petition was available at the open house for residents along SE 58th to sign and was circulated after the open house by a local resident. Of the 101 households along the street, 68, or 67%, signed the petition requesting speed bump installation.
Six 14-foot speed bumps, at 400 to 500 foot spacing, were constructed along the 0.53 mile stretch of SE 58th in June of 1995 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously spread from 20 to 31 mph, have been concentrated into the range of 20 to 28 mph. The 85th percentile vehicle speed before the project was 32 mph. After bump construction the average 85th percentile speed was 24.9 mph and ranged from a low of 22 mph (near the bumps) to a high of 28 mph.
Traffic volumes measured before bump construction were 600-1100 vehicles per day (vpd), with higher volumes North of Woodward. Traffic volumes measured after bump construction showed no significant change from the pre-bump volumes. Adjacent streets identified as unwanted diversion routes showed no significant increases in traffic volume.
Traffic calming on SE 58th Avenue has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.