The multimillion-pound Viper project, run by the Vehicle and Operator Services Agency (VOSA), uses a combination of automatic number plate recognition (ANPR) software and 'weigh-in motion' strips embedded in the road. A network of 14 checkpoints is to be created by 2008. Vehicles are weighed as they cross the sensors and the information is cross-referenced with the lorry specification and loading limits provided through the ANPR system. Cameras also take a side-view photograph to provide further identification.

Trials of the technology, which concluded last year, showed a 700 per cent increase in detection of overloaded trucks in six months.

All lorries that are pulled over are automatically weighed, but previously Viper inspectors had to rely on sight alone to assess passing traffic, says VOSA senior business owner Kevin James. In the trial our success rate was 100 per cent - every vehicle detected as overloaded subsequently proved to be so," he said.

VOSA is working with the Department for Transport, the Highways Agency and police groups to implement the Viper initiative. The main aim is to improve safety, says James. Overloading a lorry changes its handling characteristics and that can make them dangerous," he said.

If the project is as successful as the trial, it could be expanded a further tenfold, says James.