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Speed Table Installation Overview
What is a speed table and are they effective?
Speed tables are elongated speed humps with a flat 10' wide area on top with similar design as a raised marked crosswalk. They are typically placed upon low-speed, straight residential streets that do not have intersections to reduce vehicle speeds and neighborhood cut through traffic.
How does the City decide where to install traffic circles?
The Traffic Safety Committee found the need for traffic calming on neighborhood streets based upon documented conditions. These streets are typically wide, straight/flat neighborhood streets conducive to cut-through traffic and/or speeding. All roadways evaluated for speed tables have a posted speed limit of 25 mph. The streets selected all have a larger percentage of drivers traveling well above the posted speed limit. The goal of traffic circle installation is to reduce vehicle speeds through neighborhoods and discourage drivers from using these streets to cut through neighborhoods.
Where are traffic circles now in place? Are they effective?
The City has installed three (3) sped table projects:
- 25th Ave NE (north of 176th ST NE)
- 116th ST NE (east of 51st Ave NE)
- 121st ST NE (east of 51st Ave NE)
The speed tables have been successful in reducing traffic speeds, especially Excessive Speeds defined as drivers traveling greater than 10 mph over the speed limit.
Speed Table Installation Results
Location | Average Daily Traffic (ADT) |
Average Speed (mph) |
85% Speed (mph) |
% of vehicles traveling greater than 10 mph over 25 mph speed limit |
---|---|---|---|---|
All Locations Average (Pre-installation) |
1728 | 29.4 | 38.1 | 21.2% |
All Locations (Post Installation) |
1642 | 25.1 | 29.6 | 2.3% |
Decrease | 86 | 4.3 | 8.5 | 18.9 |
% Decrease |
5.0% | 14.6% | 22.3% | 89.2% |