The Traffic Calming Program (TCP) undertook a Streamlined Speed Bump Project in the summer of 1996 to address traffic problems identified by residents along SE Harney from 82nd to 89th Avenue.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using SE Harney closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only devices considered for streets like SE Harney, 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 affecting access. It is not an intended goal to reduce traffic volume on low-volume Local Service Streets.
SE Harney serves a primarily single family residence neighborhood. 82nd Avenue, to the west, is a Major City Traffic street. 89th Avenue, at SE Harney's east end, is a Local Service street. SE Harney has neither sidewalks nor curbs. A portion of the daily traffic on SE Harney is believed to be cut-through traffic due to traffic congestion on 82nd Avenue and SE Flavel Street, a parallel street to the north.
Residents along SE Harney were invited to an open house January 23, 1997 to review and comment on the proposed speed bump installation. Three attended the open house. All of those who attended expressed approval for the proposed project. A petition was available at the open house for residents along SE Harney to sign and was circulated after the open house by a local resident. Of the 46 households along the street, 40, or 86.9%, signed the petition requesting speed bump installation.
Four 14-foot speed bumps, at 420 to 460 foot spacing, were constructed along the 0.34 mile stretch of SE Harney, 82nd to 89th Avenue, on May 18, 1997 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 26 and 31 mph, have been shifted into the range of 17 to 25 mph. The average 85th percentile vehicle speed before the project was 35.7 mph. After bump construction the average 85th percentile speed is 25.6 mph and ranges from a low of 22 mph (near the bumps) to a high of 27 mph.
Traffic volumes measured before bump construction averaged 670 vehicles per day (vpd). After bump construction volumes measured 520 vpd, with higher volumes near 82nd Avenue. Traffic volumes measured on side streets parallel to SE Harney showed no significant increases from volumes before speed bump construction.
Traffic Calming on SE Harney, 82nd to 89th Avenue has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.