City of Chula Vista
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Speeding
Speed Studies
When Traffic Engineering receives a request related to elevated speeds on a road segment, staff first reviews the collision history to see if there were recent crashes on the street. Then, staff typically installs a low-profile radar speed data collector that drivers rarely notice to gather objective speed data.
If the 85th percentile speed (the speed 85% of vehicles are traveling at or below) is 10 mph or more above the posted speed limit (or 35 mph on a residential street), or if two or more collisions occurred on the segment in the last three years, staff considers modifications to potentially slow traffic. For all speed requests, Traffic Engineering staff notifies Chula Vista Police for enforcement and reviews existing signage and striping to see if it meets City and California standards.
Speed Humps and Other Traffic Calming Measures
As mentioned above, there are certain conditions where traffic calming measures such as speed humps are applicable. Staff follows City Council Policy #576-18 "Installation of Speed Humps for Residential Streets" (PDF) to determine whether speed humps are applicable. Please fully review this policy at the above link if you are interested in having speed humps on your street.
How Speed Limits Are Determined
The California Vehicle Code sets general speed limits throughout California. Most residential streets that do not have a posted speed limit have a "prima facie" speed limit of 25 mph, meaning that is the speed limit if there is no sign and the street meets the conditions for a residence district. All other speed limits are determined by an Engineering and Traffic Survey, which is an engineering document of existing traffic volume and speed, collision history, road conditions, and land uses on a road segment.
The California Vehicle Code and the California Manual on Uniform Traffic Control Devices provide the rules and guidelines for how an Engineering and Traffic Survey is prepared. The starting point is the 85th percentile speed (the speed 85% of vehicles are traveling at or below) when there is no congestion on the road. That speed may then be adjusted based on the above conditions and state regulations to arrive at the official speed limit that is recommended to the Traffic Safety Commission and City Council.
For more information about speed limits, please see the below references:
- California Vehicle Code
- California Manual on Uniform Traffic Control Devices
- Caltrans Reference for Setting Speed Limits
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