Speed Limits
Establishing speed limits and signs are part of state law complying with California Vehicle Code (CVC) and federal law complying with Manual of Uniform Traffic Control Devices (MUTCD). In California, an Engineering & Traffic Survey (E&TS) that establishes a speed limit for any roadway at the 5th mph increment of the 85th percentile speed needs to be conducted to justify posted speed limits. These E&TS need to be conducted every five up to seven or ten years on particular criteria per CVC.
FAQ-Why not keep the existing speed limit signs arbitrarily low to slow the speed of traffic?
Question: Why not keep the existing speed limit signs arbitrarily low to slow the speed of traffic?
Answer: This is a misconception. Many before and after studies have found that changing the speed limit signs does not change how fast Americans drive. The best known study is the “Parker Report”, (Report No. FHWA-RD-92-084: The Effects of Raising and Lowering the Speed Limit). The federal Department of Transportation hired a consultant to prove that low speed limits slowed traffic and improved safety. The study looked at data from 100 sites in 22 states where speed limits were either raised or lowered. Counter to the hypothesis of the federal DOT, the study found low speed limits had no effect on traffic speed.