Dead tired or dead drunk? Fatigue kills - The 'morning after' drill

Rightly, more attention is now paid to the effects of drink on our driving the next day, but our research shows that a bad night's sleep can also take its toll.

Peter's final test was at 7.10am. By then, his blood alcohol was below the UK limit, but at the 50mg threshold enforced by most other European countries and under consideration by the UK government.

He was still 26% worse at holding a steady distance than he had been when sober and rested, and 18% worse at staying in lane.

In fact, Peter almost drove into the back of a truck before taking avoiding action at the last moment. 'This was closer to an accident than at any other point in the trial,' says Professor Parkes.

After just four hours' sleep, David's driving suffered, too. His ability to stay in lane and hold a steady 60mph through the bends was worse than at 2am.