Sequence data for the traffic lights on the A725: FOI release

Information requested

The traffic light sequence data for the traffic lights on the A725 southbound, at the slip road to the M8 (marked on map attached to email), on 5/5/23 between 7am and 9am.

The traffic light sequence data for the traffic lights on the A725 northbound, approaching the junction to take the slip road onto the M8 (marked on map attached to email), on 5/5/23 between 7am and 9am.

Response

While our aim is to provide information whenever possible, in this instance Transport Scotland does not have the information you have requested. This is because the timings are controlled by a system called Microprocessor Optimised Vehicle Actuation (MOVA), which determines the amount of green light time to give to a particular direction. A more detailed explanation is provided below.

In addition, Scottish Roads Partnership (SRP), the project contractor for the M8 M73 M74 Motorway Improvement Project have attached a traffic signal staging diagram (see annex A) that outlines the sequencing of these traffic signals. In view of this, SRP are unable to determine the exact sequencing and timings of the traffic signals on any given date, as the MOVA system is variable depending on the traffic flows its sensors detect approaching the junction.

It may be helpful to explain that MOVA has two modes of operation depending on the road conditions – these are congested and uncongested (free-flowing). In free-flowing mode, the aim of MOVA is to disperse any queues which have built up on a red signal, it then assesses the traffic flows approaching on each arm of the junction and calculates if extending the current green light time would be beneficial.

If it is beneficial, then the current green light time is extended and the calculation is repeated. This continues until there is no benefit in extending the green light time and the signals move to the next stage.

When the network is congested, MOVA operates in a capacity maximising mode. This assesses which approaches are overloaded and how efficiently the green light time is being used and seeks to determine a set of signal timings which will maximise the throughput of the junction under the current conditions. Shawhead Junction (North, Central & South) is automatically controlled by three sets of intelligent traffic signal systems, microprocessor optimised vehicle actuation (MOVA), that are synchronised with each other. It should be noted that MOVA has no function which would allow the control of driver behaviour.

It should be noted that there have been no changes to the traffic signal sequencing here, including the green ‘Right Turn’ arrow since the traffic signals date of installation on 10 October 2017.

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The Scottish Government is committed to publishing all information released in response to Freedom of Information requests. View all FOI responses at https://www.gov.scot/foi-responses.

FOI 202400436085 - Information released - Annex A

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