How are speed limits decided?
Most residents know that there are certain prima facie speed limits established by California law, including the 25 MPH speed limit in residential neighborhoods, and the 25 MPH limit in school zones when children are present. However, understanding how speed limits are determined on other roadways is not as universally understood.
California law, primarily housed within the CVC, requires speed limits be set based on Engineering and Traffic Surveys, with some exceptions such as residential roadways, alley ways, and school zones as noted above. The CVC requires speed limits be set near the 85th percentile speed
The 85th percentile speed is the speed at which 85 percent of drivers are currently traveling at or below. There following parameters are required when determining the 85th percentile:
- Actual speeds at which drivers are currently traveling on the roadway are measured to calculate the 85th percentile speed.
- All data for recommended changes was collected during normal operations (before COVID).
- City staff have very little leeway to adjust the recommended posted speed limit from the measured 85 percentile speed.
Traffic engineers can reduce posted limits by a 5 mph maximum, if justified by certain roadway conditions such as crash history, driveway density, as well as pedestrian and bike activity.
The Citrus Heights City Engineer continues to recommend the lowest posted speed limits allowable under the current State requirements and law.