In the 1960's and early 1970's, traffic signals and their controls consisted mainly of basic relay switches, transferring power to the signals in a pre-arranged sequence.  Today, the traffic signal controllers are computers that monitor over 300 data inputs from each signalized intersection.  Sensors buried in each lane and the approaches to the intersection send vehicle count data, arrival rates (density) and other information to the controller, usually located in a box on the corner of the intersection. 

 

Today, a modern traffic signal installation (equipment and labor) can easily cost $30,000.  The days of placing a traffic signal at any location (whether justified or not) are over. 

 

The Federal Manual on Uniform Traffic Control Devices (M.U.T.C.D.) has 11 warrants for the installation of a traffic control signal.  The warrants look at such items as traffic counts, delay and density of traffic, and accidents.  The warrants also consider intersection location, i.e. schools and their relationship to other intersections. 

 

The satisfaction of one of the warrants justifies consideration of, but do not mandate, placement of a traffic signal. 

 

For more information on traffic signals, please contact the City Engineer at (205) 333-3002 or e-mail.