Speed table installation overview

In 2017, the City, for installation on roadways where traffic circle installation would not be recommended per City policy, performed pilot studies of speed tables on three streets.  The speed table pilot was effective and the devices are an accepted City option where traffic circles are not appropriate.

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. 

Speed Table Standard Detail

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 many speed table projects, some locations include:

  • 25th Ave NE (north of 176th ST NE)
  • 116th ST NE (east of 51st Ave NE)
  • 121st ST NE (east of 51st Ave NE)
  • 60th DR NE (Grove ST to 88th ST NE)
  • 92nd ST NE (State Ave to 46th DR 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

Average Daily
Traffic (ADT)
Speed (mph)
85% Speed
% of vehicles
traveling greater
than 10 mph over
25 mph speed limit
All Locations Average
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%