Question to the Department for Transport:

To ask the Secretary of State for Transport, if he will make an assessment of the effect of traffic lights at four-way junctions where only one light is green at any time on (a) capacity and (b) flow at those junctions.

The management of traffic light junctions, including operational strategies and timings, is a matter for local traffic authorities. As such, the Department does not carry out such assessments.

The Department has always advocated the use of traffic responsive systems, and junction designs that optimise operation to reduce unnecessary delays and maximise junction capacity as far as possible.

The Department has recently updated its guidance on the design of traffic light junctions, in Chapter 6 of the Traffic Signs Manual. This makes clear that the most efficient way to operate a junction is to adopt sequences and techniques that allow one or more arms to run at the same time, to keep traffic moving safely. Chapter 6 is available to download from:

https://www.gov.uk/government/publications/traffic-signs-manual