SPEED camera bosses today defended spending £70,000 on an enforcement system that will only be in place for the next eight weeks.Suffolk SafeCam said the devices, which measure the average speed of motorists between two fixed points, are the best way to ensure the safety of workers on Ipswich's Orwell bridge.

SPEED camera bosses today defended spending £70,000 on an enforcement system that will only be in place for the next eight weeks.

Suffolk SafeCam said the devices, which measure the average speed of motorists between two fixed points, are the best way to ensure the safety of workers on Ipswich's Orwell bridge.

The system, which would cost at least £250,000 to install permanently, is designed to deter drivers from traveling more than 40mph.

The Speed Check cameras were chosen instead of the common £50,000 Gatsometer fixed cameras, installed at nine sites around the county. These would have cost about £340 a week to hire.

Michelle Finnerty, of the group, said: "This is the first time that this camera system has been used in Suffolk and was selected because of the importance of enforcing the 40mph speed limit throughout the whole safety zone.

"A disadvantage of fixed cameras is that some drivers choose to speed up immediately after they have passed them. The cameras in place on the Orwell bridge ensure that a continuous safety zone is created."

Ms Finnerty added the nature of the work being carried out on the 22-year-old structure means it is vital people keep within the limit at all times.

She said: "The ongoing maintenance work may not be immediately obvious to road users, as much of the inspection is taking place inside the bridge and underneath it, utilising teams of abseilers.

"To ensure the safety of road users and the workforce, it's vital drivers adhere to the speed limit for the entire section of the safety zone. One of the most effective ways this could be done in this instance is with the cameras that measure average speed between two set points."

This is the first time this type of camera has been used in Suffolk and they will be removed when the safety work is complete. It is expected to take between six and eight weeks.

There are no current plans to install them at other sites in the county, although there are currently 40 elsewhere in the UK.

Suffolk SafeCam, which paid for the installation of the cameras, is funded through speeding ticket fines, with any excess going to the Treasury.