Speed Limits

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"How does the City determine speed limits?"

Speed Limit Sign

This is one of our most common questions. The process of setting speed limits is consistent with the legal requirements of the California Vehicle Code, so it is consistent across California. The process is as follows:

1. Staff collects speed data from 100 vehicles using a radar or laser gun. The vehicles included in the survey are free-flowing, and not during periods of traffic.

2. The survey identifies an 85th percentile of traffic, or the speed of 85% of traffic on the street. 15% of the traffic exceeds this speed.  

3. Staff investigates recent collisions and considers other factors, as allowed in the Vehicle Code.

4. The survey is put on a form, signed and stamped by a professional engineer.

5. The signs required by the survey are posted. 

This means motorists set the speed limits for segments of road. This survey occurs on all City streets except residential/local streets which meet the 25 MPH prima-facie speed. The speed limit for any segment of road is set at the nearest 5 mph increment of the 85th percentile speed of the speed survey.
For example, an 85th percentile speed of 41.5 on a speed survey would establish a speed limit of 40 mph. An 85th percentile speed of 43.8 on a speed survey would establish a speed limit of 45 mph. To read more about this process, see the manual distributed by Cal Trans on speed limit requirements. 
After the speed limit is adopted by City Council and appropriate signs installed, the police department can legally enforce the posted speed limits with the use of radar. If no physical changes occur on the roadway, the speed survey is considered valid for a period of 7 years and can be extended up to 10 years if conditions remain constant. The road survey process is repeated every 7-10 years for all City streets except residential/local streets which meet the 25 MPH prima-facie speed.

See the map on the Traffic Counts page for established speed zones in the city.


"What can be done to slow down speeding traffic on my street?" 

If vehicles seem to be going too fast on a City street, we'd like to know about it. First, staff will conduct a speed survey to quantify the speed of traffic. This is the same procedure used to set a speed limit.

 In some cases, speeding is not actually occurring on the street and the resident is informed of these findings. When the data shows speeds exceeding the speed limit, the education and enforcement process begins. The Transportation Division contacts the Traffic Safety division of the Police Department so we can work together and address the concerns. 

One resource utilized by Public Works is a Radar Trailer. This device encourages compliance with the speed limit and actively educates drivers. These devices are usually placed on the road for a week prior to or along with police enforcement. This device:Radar Trailer

  • Is easy to read
  • Attracts drivers' attention
  • Is Cost-effective
  • Is Mobile and simple to deploy on short notice
  • Does not issue automated speeding tickets


Speed Feedback SignSome areas have a permanent V-calm Radar sign, which accomplishes a similar goal to the trailer, but in a permanent installation. These signs are most effective in critical areas, such as school zones, or areas with unique roadway design.

Neither of these devices issue automated speeding tickets.

A permanent solution to speeding on major and collector streets could be striping modifications. One example of a striping modification is called a “road diet” or road narrowing. A road diet involves reducing the number of lanes, reducing lane width and/or adding edge striping to the roadway.