More and more lorry drivers are manipulating the on board computers which measure their driving time - putting their lives and the lives of other road users at risk. The DVSA has told 5 live Investigates there has been a 21 per cent increase in the number of drivers caught using cheat devices. But the so-called 'interrupters' don't just allow drivers to drive tired - they stop speedometers and anti-lock braking systems from working which could have catastrophic consequences on the roads.