The union threatened a legal challenge under new human rights legislation because the vehicles could be tracked out of office hours. But Bill Edwards, managing director of Brunel Carriage, which runs a fleet of more than 200 Mercedes-Benz vehicles, said: 'All our vehicles are monitored by tracking devices, but it is not a way of spying on staff. 'It is simply a good way of managing your fleet, ensuring security because stolen vehicles can be tracked if they are stolen.
'Drivers do not have a problem with it because they know that by using the system they are more efficient and they get more work. We work 24 hours a day and seven days a week, so the system has to be used all the time, but drivers do not mind.'
Companies putting together plans to install the systems have also backed the technology. Barry Lingard, fleet manager of Burton-on-Trent-based Leisure Link, which has 1,300 vehicles, said: 'I don't see what the union has to complain about. These devices are multi-functional and a theft deterrent. With them the vehicle is protected at weekends.'