Leading Article: Tolls that will tax the technologists

ELECTRONIC motorway tolls, whose introduction has been approved by the Cabinet and announced in the Budget, make good economic and technical sense. But they will be hard to sell to drivers. That is perhaps why John MacGregor, the Secretary of State for Transport, has taken a leaf out of the book of St Augustine, who asked the Lord for 'chastity and continency - but not yet'. The system he has in mind will not become a reality before the next election. Is this delay mere political cowardice?

At first sight, the idea of charging motorists a penny or two a mile to drive on a motorway, and deducting the price from an electronic 'smart card' in their cars, seems an extreme solution to the twin problems of congestion and underinvestment. Yet it is less bad than the alternatives. Issuing pounds 50 annual motorway driving permits to stick on car windscreens would raise revenue for the Government; but it would give people who bought the stickers no incentive to take the train. Old-fashioned toll-booths might work well in France or the United States; but building them in Britain would cost billions in compulsory land purchases, and would require the closure of scores of exits from British motorways. Doing nothing merely perpetuates the vicious spiral of building more roads, and seeing them clogged up within a few weeks of opening by new traffic.

Yet despite the attractions of electronic tolling systems, there is no hurry to introduce one. For one thing, the technical barriers remain daunting: an EC-funded pilot system in Cambridge went badly wrong in front of a visiting Independent journalist two months ago, even with only two cars and three electronic checkpoints. Opening a full-scale national system without long and careful trials might turn the public strongly against road pricing for good.

There are also economic arguments against haste. The current estimate is that a national network would cost pounds 1.2bn - a sum that will inevitably have to be recouped from drivers. By the turn of the century, everything may have changed. The prodigious computing power required will be cheaper. The smart cards needed in each car will be smaller. New kinds of wireless communication between cars and beacons will be feasible.

Tempting though it is to believe that Britain could gain a technological head-start over other countries that might wish to produce the equipment, the more likely outcome is that the innovator will suffer great inconvenience and wasted money. For once, prudence and political expediency go hand in hand.