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.
