Leading Article: Old bangers and clean air

THREE years ago, 160 people in London died as a result of smog caused by atmospheric pollution. At the weekend, monitoring stations once again began to detect alarmingly high figures, and experts feared a repeat of the 1991 incident this week. Thankfully, that fear has now receded after yesterday's cooler weather. But the climatic dice may fall less fortunately next time.

Some environmentalists believe that only a reversal of the Government's road building policies, and a strict new set of controls on the use of private cars, can solve the problem. They are partly right. In the long run, we must be prepared to use our cars less, and our feet and bicycles more, if we want to breathe cleaner air. The limits on exhaust emissions just imposed by the European Union will undoubtedly have to be tightened before the decade's end.

But a dramatic improvement in Britain's urban air quality could still be achieved before the next election without putting many drivers to inconvenience. This is because the great majority of cars are tolerably clean; 70 per cent of those on the roads today account for only 18 per cent of the pollution. Simple arithmetic shows that if the dirtier cars could be brought up to that standard, the total amount of air pollution could be cut almost by half, even with twice as many cars in regular use. The question, therefore, is how to make the existing rules more effective.

The most daunting obstacle to change is the tradition that new controls only apply to new vehicles. Until this is changed, nothing can be done about dirty old cars and buses that meet the rudimentary standards that applied in the 1960s or even 1950s. The Government should apply emissions standards to all vehicles, old and new, from 1998 onwards - and give drivers four years to update or junk vehicles that cannot pass the test. Small subsidies to those who trade in old cars for new, perhaps on the French model, might help.

Reform is also needed to the way exhausts are tested. The test that cars must pass to win an MoT certificate should be carried out not at idling speed as now, but in conditions that better reflect normal driving. Tests on all public-service vehicles, including taxis, minicabs, delivery vans, coaches and buses, should be carried out quarterly to reflect the very high mileages these vehicles clock up, and their concentration in the centre of London.

The police are neither willing nor able to perform the roadside checks necessary to enforce the rules. Here a lesson could be learnt from the council-run system of parking enforcement that began in London this week. A properly managed organisation, given suitable incentives, could perform the tests - and could give tickets to the drivers of dirty vehicles, or clamp them until they can prove that payment for the necessary work has been made. The results of these reforms would become apparent within months. The capital's air would be sweeter, its streets more pleasant to walk in, and its inhabitants healthier.