If you think that congestion on today’s roads is bad, take a deep breath: the worst is yet to come.

According to a report this month by the Royal Academy of Engineering, Britain’s road transport system, already one of the worst in Europe, can expect a 50% increase in cars over the next 50 years.

The report, entitled Transport 2050, says that congestion costs this country £15 billion a year — 1.5% of GDP, which is 15% worse than France and 40% worse than Germany. It claims that only a radical rethink can save the country from gridlock.

The looming crisis is thrown into sharper relief by the fact that Britain has comparatively low levels of car ownership: just 410 per 1,000 population compared with 540 for Italy, 470 for France and 520 for Germany. If Britain moves into line with these countries, gridlock will arrive that much faster.

Part of the problem, of course, is that there simply is not enough space on Britain’s roads. The construction of roads has not kept pace with the growth in traffic. In terms of motorway capacity per head of population

Britain ranks 14th in western Europe, ahead only of Ireland, and motorway coverage as a percentage of the country’s land mass puts us at 11th, just above Greece.

So how have the road planners got it so wrong? In the 1950s and 1960s planners tried to forecast traffic levels and build new roads accordingly. The policy saw the construction of the M1 begin in 1958, followed by assorted motorways and dual carriageways, until the 1990s when ever increasing numbers of cars forced policy makers to admit that they could not go on building themselves out of trouble. The 1992 Earth Summit also required national governments to consider transport planning in the context of sustainability.

Suddenly, rather than building roads, policy makers decided that culling the car and promoting public transport was the way forward. “I will have failed if in five years’ time there are not many more people using public transport and far fewer journeys by car,” said John Prescott, the deputy prime minister, in 1997 when he unveiled his plan for a “joined up transport system”.

The effects of this policy change on road construction were clear. The 1989 Roads For Prosperity programme contained more than 500 planned schemes; nine years later the 1998 New Deal for Trunk Roads programme contained just 37. The past 20 years have seen a 30% growth in car ownership with just a 0.06% increase in the network of major roads.

But the number of cars has continued to rise and by 2000 the government had to admit as much. The current transport policy is a long way from Prescott’s vision of reduced car journeys.

In fact the government has reverted to a road building programme on a scale not seen since the 1980s. Some £59 billion has been allocated to roads over the next 10 years and everywhere stretches of dual carriageway used as bypasses or relief roads are being joined up to form new trunk roads traversing the countryside. At the same time formerly much-vaunted public transport schemes, such as an integrated road and rail network, are being shelved as too expensive.

The Highways Agency was recently criticised by the National Audit Office for being over-cautious and not introducing traffic management schemes such as car sharing that have been successful in other countries. But under the guidance of Denise Plumpton, its newly installed director of information, the agency says it is determined to improve the quality of information it provides to help drivers beat congestion.

For many this is all too little late. “The key requirement to build a sustainable transport system is true cost charging,” says the Royal Academy of Engineering report.

And that means a system of pay as you go.