Highways England is remaining tight-lipped about whether average speed cameras on the Sheppey Crossing have been switched on.

The speed limit on the bridge returned to 70mph after the temporary 50mph signs were removed on Tuesday, March 21.

Work on the £350,000 scheme, which began on March 13, was carried out after the agency completed a 17-month safety review of the crossing last year.

The digital cameras were due to be working by the end of March. However, this week Highways England refused to confirm if the cameras were on and, if not, when they would be.

A spokesman said: “We won’t be providing a running commentary on the speed cameras. The speed limit is enforceable already and the cameras will be switched on as soon as they have completed the necessary checks.”

Once testing has been carried out, the cameras will fall under the remit of the Kent and Medway Safety Camera Partnership, made up of Kent Police, Kent County Council, Medway council and Highways England.

The national speed limit will be enforced using a SPECS Vector camera system provided by Jenoptik.

Using automatic number plate recognition, they work by measuring the time it takes to pass between the cameras over a fixed distance, which provides an average speed for each vehicle.

The system passes the two images and details of any offences it records straight to police for processing.

"We won’t be providing a running commentary on the speed cameras. The speed limit is enforceable already and the cameras will be switched on as soon as they have completed the necessary checks" - Highways England

Drivers risk a minimum fine of £100 and three penalty points for breaking the limit. The alternative is a speed awareness course, costing £87. Anyone caught doing over 95mph will be summonsed to court.

Highways England imposed a 50mph maximum on the bridge and approaches in July 2015 after an inquest into the deaths of mother and son Deborah and Marshall Roberts.

However, it discovered the accident rate had increased since introducing the lower limit.

Arvind Patel, Highways England’s service delivery manager, said: “We are absolutely committed to ensuring that the Sheppey Crossing operates safely and, after a thorough independent review of its safety, we have decided to reinstate the 70mph national speed limit across the bridge.

“However, it is important that people stick to the speed limit, which is why we are introducing average speed enforcement cameras at the same time.

“The change is part of a package of measures that we are taking in the short, medium and long term to ensure that the Sheppey Crossing remains as safe as possible for the thousands of drivers that depend on it every day.”

The agency said it would also install variable message signs, a weather station to monitor wind and fog and CCTV to further improve the crossing’s safety costing a further £2 million.