A725 central junction traffic light sequence: EIR release

Information requested

The following in relation to the central junction on the A725 that has the A8 Eastbound on/off slip roads:

1. how the traffic light sequence for the Right Signal in the Junction operates; and
2. failing the above info being available, how the traffic light sequence for all lights in the Junction operate.

Response

As the information you have requested is 'environmental information' for the purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations. We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA.

This exemption is subject to the 'public interest test'. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

Response to your request

An exception under regulation 11(2) of the EIRs (personal information) applies to some of the information requested because it is personal data of a third party and disclosing it would contravene the data protection principles in Article 5(1) of the General Data Protection Regulation and in section 34(1) of the Data Protection Act 2018. This exception is not subject to the 'public interest test', so we are not required to consider if the public interest in disclosing the information outweighs the public interest in applying the exception.

The timings of the traffic lights at this junction 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, Annexes A and B are two traffic signal staging diagrams that outline the sequencing of these traffic signals. In view of this, Transport Scotland is 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.

About FOI

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

EIR 202400432270 - Information Released - Annex A

File type

1 page PDF

File size

481.4 kB

EIR 202400432270 - Information Released - Annex B

File type

1 page PDF

File size

809.4 kB