Safety and common sense should determine your driving speed, even if it means driving more slowly than the posted speed limit. Traffic engineers study streets and intersections to set speed limits. The analysis must conform to the parameters set forth in the California Vehicle Code. When determining your driving speed, it is important to remember the California Vehicle Code (CVC), Basic Speed Law:
"No person shall drive a vehicle at a speed greater than is reasonable or prudent and in no event at a speed which endangers the safety of persons or property."
All fifty states base their speed regulations on the Basic Speed Law. Under California law, the maximum speed limit is 65 MPH (55 MPH on 2 lane undivided highways). All other speed limits are called prima facie limits, which are considered by law to be safe and prudent under normal conditions. Certain prima facie limits are established by State law and include:
- 25 MPH speed limit in business and residential districts
- 25 MPH in school zones when children are present
- 15 MPH speed limit in alleys; at intersections and railroad crossings where visibility is limited and there is no railroad crossing signal device.
These speed limits do not need to be posted in order to be enforced.
Speed limits between 25 and 65 MPH are established on the basis of Engineering and Traffic Surveys. These surveys include an analysis of roadway conditions, accident records and a sampling of the prevailing speed of traffic. It is generally accepted that at least 85% of drivers operate their vehicles in a prudent, safe manner. For this reason, the speed limit is generally set at or below this speed, in 5 MPH increments. Increased safety and fewer collisions result when traffic flows at a uniform speed. Drivers are less impatient, pass less often, and tailgate less, which reduces both head-on and rear-end collisions.
The posting of the appropriate speed limit simplifies the job of enforcement officers, since most of the traffic is voluntarily moving at the posted speed. Blatant speeders are easily spotted, safe drivers are not penalized, and patrol officers aren't asked to enforce and defend unrealistic and arbitrary speed limits. Violations of unrealistic and arbitrary speed limit postings are usually dismissed when contested in court.
Speed limit misconceptions
When traffic problems occur, concerned citizens frequently ask the city to lower the speed limit. There are widely held misconceptions that speed limit signs will slow the speed of traffic, reduce accidents, and increase safety. Most drivers drive at a speed that they consider being comfortable, regardless of the posted speed limit. 'Before and after' studies have shown that there are no significant changes in vehicle speeds following the posting of new or revised speed limits. Furthermore, research has found no direct relationship between posted speed limits and accident frequency.