The Traffic Calming Program (TCP) undertook a Streamlined Speed Bump Project in the spring of 1996 to address traffic problems identified by residents along NE Ainsworth from 42nd to Lombard Street.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using NE Ainsworth closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only devices considered for streets like NE Ainsworth, 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 are 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.
NE Ainsworth serves a primarily single family residence neighborhood. NE 42nd Avenue, to the west, is a Neighborhood Collector street. Lombard, at NE Ainsworth's east end, is a Major City Traffic street. NE Ainsworth has neither sidewalks nor curbs. A portion of the daily traffic on NE Ainsworth is believed to be cut-through traffic avoiding congestion on Lombard Street.
Residents along NE Ainsworth were invited to an open house November 20, 1996 to review and comment on the proposed speed bump installation. Nineteen people attended 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 NE Ainsworth to sign and was circulated after the open house by a local resident. Of the 148 households along the street, 106, or 71.6%, signed the petition requesting speed bump installation.
Twelve 14-foot speed bumps, at 420 to 670 foot spacing, were constructed along the 1.0 mile stretch of NE Ainsworth, 42nd to Lombard, in May of 1997 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 26 and 34 mph, have been shifted into the range of 20 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 26.1 mph and ranges from a low of 21 mph (near the bumps) to a high of 29 mph.
Traffic volumes measured before bump construction averaged 580 vehicles per day (vpd). After bump construction volumes averaged 400 vpd, with higher volumes near 60th Avenue.
NE Simpson has had an increase in traffic volume and will continue to be monitored to determine if mitigation will be necessary.
Traffic Calming on NE Ainsworth, 42nd to Lombard has successfully reduced the 85th percentile closer to the posted speed and enhanced the street's safety and livability.