All traffic signals are timed with two goals in mind: 1) to make the traffic system as safe as possible for all users; and 2) to improve traffic flow. In Southern Nevada, our traffic signals typically operate under a semi-actuated coordinated schedule.  Each traffic signal controller is programmed with different timing settings, depending on time of day (morning or afternoon rush hour) or according to what is happening at the intersection at that moment. Semi-actuated operation is used to provide progressive vehicle flow through a series of controlled intersections. Each intersection controller in the coordinated system operates within a common background cycle length.