Installing a new traffic signal first requires determining if a signal is needed. If a signal is needed, then a method of funding and constructing the signal must be found. Evaluating the need for a traffic signal requires careful analysis of the accident history, the intersection geometry, and amount of traffic. The number of traffic accidents almost always increases when a signal is installed, as interruption of free flow results in an increased number of rear-end type accidents. Certain types of accidents that tend to be more severe can often be reduced by installing a signal. The analyst must weigh the different types of accidents and compare them to federal guidelines. There are certain requirements mandated by the Federal government that must be met before a signal can be installed. These requirements are called Warrants and are outlined in the California Manual on Uniform Traffic Control Devices (CA-MUTCD).
If a signal meets the warrants outlined in the CA-MUTCD, the next challenge is to find a method of funding construction and maintenance of the signal. One way this is done is conditioning new development to install a signal on a street that leads to a major subdivision. A new signal usually costs more than $250,000 to construct, and then additional dollars will be needed for annual maintenance. All intersections that meet signal warrants are put in a database and ranked corresponding to their fulfillment of warrants. Those intersections are signalized as funds become available, at a maximum of one per year. Requests for new traffic signals can be referred to the Traffic Engineering Division at 707-543-3814.