Cameras that can measure the average speed of vehicles passing through roadworks are due to be tested shortly at a site in Scotland.

Conventional speed cameras have been criticised for the bunching effect that results when drivers slow down to pass the measuring points.

These new cameras are more sophisticated and are able to detect if a vehicle increases speed along the measured stretch of the roadworks.

These units will be tested on roadworks being carried out by contractor Amey at a site near to the city of Glasgow on the M74 motorway that links Scotland and England.

The speed limit will be 40mph (64kph) and the installation is expected to increase safety levels for the construction workers.

Last year five workers were killed in the UK by vehicles being driven carelessly through road construction sites.