How Density based automatic traffic signals works fully animated.

Urban traffic control (UTC) systems are a specialist form of traffic management which integrate and co-ordinate traffic signal control over a wide area in order to control traffic flows on the road network. Integration and co-ordination between adjacent traffic signals involves designing a plan based on the occurrence and duration of individual signal aspects and the time offsets between them and introducing a system to link the signals together electronically. A traffic responsive signal control system is a means of adjusting the traffic signal settings (cycles, green splits and offsets), which optimise a given objective function, such as minimising travel time or stops, in real-time based upon estimates of traffic conditions. There are many different UTC systems in operation around the world, but they can provide the basis for an extended control system, generally termed Urban Traffic Management and Control (UTMC).

UTC systems can be used to obtain better traffic performance from a road network by reducing delays to vehicles and the number of times they have to stop. UTC systems also can be used to balance capacity in a network, to attract or deter traffic from particular routes or areas, to give priority to specific categories of vehicles such as public transport or to arrange for queuing to take place in suitable parts of the network.

Demand impacts usually reduce travel time, but reduced travel times and good network performance may increase road capacity. This may cause a shift in demand towards car use. UTC systems may not make a positive contribution to all policy objectives.