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The changing face of traffic lights with SCOOT and MOVA

Traffic lights are a vital part of modern-day street furniture that allow us to safely navigate junctions. And while we’ve all complained about getting stuck at lights or lamented how traffic would flow better if the traffic lights were removed, we probably can appreciate how these systems allow us to drive more safely.

What we probably don’t appreciate however is the amount of change traffic light technology has undergone since the first lights were installed in London in 1925. Or that continual improvement is still very much underway. Current improvements focus on Adaptive Signal Control, which adjusts the timing of traffic light phases in accordance with changing traffic patterns to minimise congestion.

SCOOT, or Split Cycle Offset Optimisation Technique, is one method of adaptive signal control where vehicles are detected as they approach a signalised junction well in advance of the stop line. This detection, from multiple junctions, is fed into a central system, which models the flow of traffic in the area. This intelligence is used to adapt the phasing of the traffic light signals in accordance with the flow of traffic, thus minimising unnecessary green phases and allowing the traffic to flow most efficiently. In this way connected traffic lights operate as a whole system to optimise the flow of traffic through an area.

When junctions are further apart, isolated junction control using MOVA is a more appropriate method of adaptive signal control. MOVA (Microprocessor Optimised Vehicle Actuation) is similar to SCOOT in that it is a method of controlling the traffic signals based on the presence of vehicles detected on the approach to a signalised junction, but this method controls one junction at a time rather than looking at traffic flow as a whole. Again the green timing at the traffic lights is adjusted according to the number of vehicles approaching the junction, and again, congestion is reduced.

So why aren’t all traffic lights using SCOOT or MOVA?

There can be additional costs associated with upgrading traffic light control to become more adaptive to the traffic approaching the junction. The standard method of traffic light control depends on the detection of vehicles at the stop line. But both SCOOT and MOVA require detection on the approach to the traffic lights. Taking this vehicle detection further up the road can have an additional cost associated with it.

But this cost can be minimised by moving away from traditional loop based vehicle detection to wireless vehicle detection. Traditional inductive loops require a large amount of expensive and time-consuming ducting and trenching. This is compounded when adding in loops further in advance of the stop line for SCOOT or MOVA as the tail from the loops needs to run from the loop back to the traffic lights. In urban areas in particular, the trenching needs to be dug by hand to avoid existing utilities pipework and cabling, which increases the cost of installation further. In contrast, wireless vehicle detection systems such as the Clearview Intelligence M100 System comprise of a sensor installed in a small (100mm x 50mm deep) hole in the centre of the carriageway, which communicates wirelessly to an access point mounted on the signal head. This significantly reduces the installation cost and disruption.

This is why TfL utilised the M100 System in their program to systematically upgrade signalised junctions in the Capital to SCOOT and how Blackburn with Darwen Borough Council were able to make savings of over £60,000 just in installation costs when they upgraded three junctions to MOVA. Similarly, Aberdeen City Council and Slough Borough Council benefited from reduced traffic disruption and traffic management costs when they upgraded to SCOOT.

So while there could be some additional costs associated with getting traffic moving quicker through adaptive signal control, these can be minimised with the use of wireless vehicle detection. And with resent research suggesting the average time British motorists spend waiting at red lights is eight minutes every day (over 2 days a year!) surely the extra investment is worth it.

Uploaded 28/11/2016