MOVA (Microprocessor Optimised Vehicle Actuation) uses an online microprocessor to optimise green stage, cycle time, and control strategy to minimise traffic queues at signal-controlled junctions according to prevailing traffic conditions. This self-optimising traffic signals control system was developed at the Transport Research Laboratory (TRL), and is now coming into use at free-standing junctions in the UK. This paper reports its application to a signalised roundabout, at Junction 24 on the M4 motorway, which was formerly controlled by conventional cableless linking. It also describes how two signal controllers there were replaced by one controller operating two linked MOVA units. The introduction of these improvements brought significant improvements at this junction: (1) reduced delays and increased capacity in peak periods; (2) when lamps are not normally timed to be on, detecting queues and automatically controlling signals to clear queues quickly and effectively; and (3) flexibility to control the formation of residual queues, to prevent roundabout and motorway blocking near access roads. The resulting junction control strategy has been adaptable and very effective, and much better than traditional cableless linking. It was made possible by the recent MOVA3 enhancement to MOVA.
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