Queensferry crossing speed restrictions: FOI release

Information requested

You stated "Can you explain the reason for the speed restrictions being constantly imposed on the Queensferry crossing, I know it states Congestion on the signage but that is not the case, leading up to the bridge speed restricted to 40 mph with tailbacks on the carriageways on the approach to the bridge for some considerable distance, half way over the bridge you can clearly see there is no congestion on the second half of the bridge as the speed restriction has been remove from there on the road ahead is also free flowing this is the same situation on both directions it is evident the congestion is being cause by the speed restriction leading up to the bridge because there are no adverse weather events no road works and no breakdown an explanation is required so I may put it to my local MSP, This has been an ongoing situation regarding the bridge"

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 information you requested is not collated in such a way as to answer your question. This is a formal notice under section 17(1) of FOISA that the Scottish Government does not have the information you have requested.

This exemption 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 exemption.

Notwithstanding the above, you may find the following information helpful.

At the Queensferry Crossing, an Intelligent Transport System (ITS) is in operation and includes overhead gantries, spaced regularly along the route. These gantries provide motorway signals and variable message signs to control traffic and inform road users. Mandatory variable speed limits are applied when necessary – e.g. during incidents or when significant congestion occurs. To support the operation of the ITS, CCTV cameras, journey time cameras and enforcement cameras including automatic number plate recognition are also used. The speed limits are set automatically using SSA (Signal Sequencing Algorithm) which is based on Chapter 8 Traffic Management of the Traffic Signals Manual (Traffic signs manual - GOV.UK at www.gov.uk)

The ITS allows mandatory variable speed limits to be applied so that vehicle speeds can be managed during congestion and in response to incidents such as breakdowns. Variable speed limits keep traffic moving by controlling the flow of vehicles when a road is congested. This should reduce the number and speed of vehicles reaching a congested location, which should improve safety and prevent the congestion/queue increasing. Using CCTV cameras and data from traffic flow detectors, Traffic Scotland’s National Control Centre can monitor traffic levels and lower speed limits to reduce traffic build-up. These restrictions are set by the Traffic Scotland System, which conforms to Chapter 8 standards and deployed in a consistent manner for safety reasons. Depending on the circumstances, restrictions can extend / retract based on impacts occurring in real-time and therefore can change depending on roadside conditions.

Transport Scotland acknowledge that it is important that dynamic messaging is timely and accurate, however understands that driver frustration should be avoided where possible. We are aware of an issue with a traffic flow detector on the M90, which has been activating the reduced speed limit when this was not required by traffic conditions. This detector has been deactivated and is now being programmed for repair by a specialist contractor. In addition, Transport Scotland has instructed Traffic Scotland to undertake sample checks of sign setting and removal on the motorway network, including between Fife and Edinburgh. That process is on-going. Traffic Scotland welcomes reports, which are helpful, as any specific examples, particularly during weekdays, allow it to pinpoint the exact issues so that the system can be refined / improved where needed.

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