Final Project Evaluation
The Traffic Calming Program (TCP) undertook a streamlined speed bump project in the Summer of 1996 to address traffic problems identified by residents along NE Fargo from 117th to 122nd Avenue.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using NE Fargo closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only devices considered for streets like NE Fargo, 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.
NE Fargo, 117th to 122nd Avenue, serves a single family residence neighborhood. 117th, to the west, is a Neighborhood Collector street. 122nd, at NE Fargo's east end, is a Major City Traffic street. NE Fargo, 117th to 122nd Avenue, has both sidewalks and curbs. There is also a horizontal curve at the west end. A large portion of the daily traffic on NE Fargo is believed to be cut-through traffic.
Residents along NE Fargo were invited to open houses' September 9-11, 1996 to review and comment on the proposed speed bump installation. Seven households were represented at the open houses. The majority of those who attended expressed approval for the proposed project. There was concern expressed that the bumps were too abrupt. A petition was available at the open house for residents along NE Fargo to sign and was circulated after the open house by a local resident. Of the 28 households along the street, 20, or 71.4%, signed the petition requesting speed bump installation.
Three 14-foot speed bumps, at 400 to 480 foot spacing, were constructed along the 0.23 mile stretch of NE Fargo, 117th to 122nd Avenue, in May and June of 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 85th percentile vehicle speed before the project was 33 mph. After bump construction the average 85th percentile speed is 26 mph and ranges from a low of 24 mph (near the bumps) to a high of 28 mph. Before installation of the speed bumps 64% of drivers exceeded the posted speed limit of 25 mph and 9.8% exceeded the limit by 10 mph or more. Since bump construction 20% of drivers exceed the posted speed limit and 1.4% exceed the limit by 10 mph or more.
Traffic volume measured before bump construction was 570 vehicles per day (vpd). After bump construction volumes averaged 460 vpd. Traffic volumes measured on side streets adjacent to NE Fargo showed no increases from volumes measured before speed bump construction.
Traffic Calming on NE Fargo, 117th to 122nd Avenue has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.