18 November 2002: Run-flat tyres could be underpinning an increasing number of new cars in coming years, but there are some safety concerns about the imminent end of the spare, which the boss of the Michelin tyre group says will have 'gone the way of the crank-handle' by 2010.

Using run-flats, in cars such as the Lexus SC430 and the new BMW Z4, frees up boot space and also cuts weight, helping fuel economy. The tyres don't collapse if punctured and can be driven up to 150 kilometres to be repaired.

But US safety experts at the National Highway Traffic Safety Agency (NHTSA) say they are uncertain about how cars will fare in crash tests if the spare is left out. Current tests are run with the spare in place, and in effect it is part of the design of most cars in safety terms, acting as a 'buffer' in a rear impact.

Bob Lutz of General Motors says the spare is still part of the 'rear crush system' on many cars, and Volvo also maintains that the spare is 'definitely' part of the rear energy absorbtion system.

Ford is investigating whether missing spare tyres contributed to policemen being killed in recent incidents when their patrol cars were hit from behind and burst into flames.