The Traffic Calming Program (TCP) undertook a Streamlined Speed Bump Project in the Spring of 1995 to address traffic problems identified by residents along Montana Avenue from Buffalo to Portland.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using Montana Avenue closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only device considered for streets like Montana Avenue, 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.
Montana Avenue serves a single family residence neighborhood. Buffalo Street, to the north, is a Local Service Street. Portland Boulevard, at Montana Avenue's south end, is a Major City Traffic Street. Montana Avenue straight, fairly level and has sidewalks and curbs. A significant portion of the daily traffic on Montana Avenue is believed to be cut-through traffic due to the Fred Meyer store just north of Buffalo Street.
All residents along Montana Avenue were invited to an open house December 6, 1995 to review and comment on the proposed speed bump installation. Seven households were represented at the open house. Those who attended expressed approval for the proposed project. A petition was avail
able at the open house for residents along Montana Avenue to sign and was circulated after the open house by a local residents. Of the 54 households along the street, 40, or 74%, signed the petition requesting speed bump installation.
Four 14 -foot speed bumps, at 430 to 490 foot spacing, were constructed along the 0.36 mile stretch of N Montana Avenue in April of 1996 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously spread between 23 and 28 mph, have been shifted into the range of 23 to 25 mph. The average 85th percentile vehicle speed before the project was 30 mph.
After bump construction the 85th percentile speed ranged from a low of 17 mph (near the bumps) to a high of 28 mph. The average 85th percentile for the street after speed bump construction is 23 mph.
Traffic volumes measured before bump construction were 1000-1100 vehicles per day (vpd). After bump construction volumes measured 900-1000 vpd. Maryland Avenue, to the west, was the only street identified as a possible diversion route. Volume counts on Maryland Avenue showed an increase of 50 vehicles per day, well below the allowable threshold of 150.
Traffic Calming on N Montana Avenue, Buffalo to Portland, has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.