Vehicle traffic congestion is one of the serious problems facing municipal administrators. The search for increased efficiency has led to the development of traffic engineering as a science.The digital computer as a traffic engineer's instrument is relatively new, but appears to be a natural successor to analog systems, which have in turn sprung from fixed time systems and noncoordinated devices. Today's computer systems are the first to link all the elements of a closed-loop automatic control system; namely, information gathering, decision-making, execution, verification, and evaluation.In particular, the system at San Jose has shown that a computer system can be readily adapted to handle different control techniques, and give almost immediate feedback in concrete terms. A system of measuring stops and delay, developed at San Jose, can be used to evaluate traffic in both a microscopic and macroscopic sense. The use of these values has demonstrated how seemingly small improvements can have a very large effect on the costs to the motoring public.