Speed limits are established to provide motorists with clear direction to drive at a speed that will facilitates safe and orderly flow of traffic under normal conditions.
California has a “Basic Speed Law” that states “No person shall drive a vehicle upon a highway at a speed greater than is reasonable or prudent having due regard for weather, visibility, the traffic on, and the surface and width of, the highway, and in no event at a speed which endangers the safety of persons or property.”
The maximum speed limit on most California highways is 65 mph. Unless otherwise posted, the maximum speed limit is 55 mph on two-lane undivided highways and for vehicles towing trailers.
Speed zoning is the practice of establishing speed limits that are reasonable and safe for specific sections of roadway. Non-statutory speed limits are established by an Engineering and Traffic Survey. This Survey determines an appropriate speed limit considering factors such as the type of adjacent development, pedestrian and bicycle activity, roadside conditions, reported collision history, and the prevailing speed of traffic. The prevailing speed is that speed which 85 percent of the motorists are traveling at or below. The prevailing speed is utilized as a reference to establish speed limits based on the concept that most motorists can be relied upon to drive at a reasonable speed. Studies have shown that setting arbitrarily low speed limits results in wholesale violations, and does not necessarily result in lower driving speeds.