CA AB1938

Authorizes Caltrans or local authorities to lower speed limits by 5 mph from the nearest 5 mph increment of the 85th percentile speed when rounding down, provided the reasons are documented in an engineering and traffic survey.

Caps the total speed limit reduction at 12.4 mph from the 85th percentile speed across all applicable provisions.

Allows local authorities to retain currently adopted speed limits or restore immediately prior adopted speed limits without further reduction under specified conditions.

Exempts speed limits adopted under Sections 22358.7 and 22358.8 from the definition of "speed trap," removing the requirement for engineering and traffic surveys to justify enforcement using radar or electronic devices.

Requires local authorities to issue only warning citations for violations exceeding the speed limit by 10 mph or less during the first 30 days that a lower speed limit takes effect under these provisions.