MOTORISTS face many more years of traffic chaos because one third of planned road improvement schemes have been delayed by up to five years.

Costs for the Government’s road-building programme have risen so much that many industry experts believe that some of the most delayed schemes may have to be scrapped, despite long-term commitments to carry out the work. The total budget for more than 40 of the country’s most ambitious road projects has risen by two thirds, pushing the programme’s cost up by £1.5 billion.

Of those road schemes that are already over budget, at least 14 are subject to delays of between one and five years, according to information obtained by the The Times. More are likely to be postponed because of spiralling costs and prolonged planning problems.

One of the most controversial schemes — to build a road tunnel under Stonehenge — will cost an extra £345 million, three times more than forecast, and a decision on the plan has been deferred until October.

Chris Grayling, the Shadow Transport Secretary, said: “The Government continues to spend substantial amounts of taxpayers’ money with very little to show for it. They have made a whole series of promises about what they are going to do but these promises have not been realised.”

The Highways Agency is investing about £3.8 billion in road building over the next three years, out of a total expenditure on road improvements of £10 billion.

Of the 14 delayed schemes, some have overruns of more than £100 million. For example, construction of the A46 Newark to Widmerpool — a new 17-mile dual carriageway — was due to begin in 2006-07. Now, with a 168 per cent increase in budget — that is, a rise of £138 million — the start of works is programmed for 2008-09. Work on the A3 Hindhead upgrade should have begun last year, at a planned cost of £107 million. Now the project, the latest cost of which is £239 million, is due to start in 2008.

The Highways Agency said that the nature of the programme meant that some schemes could fall behind or progress quickly. But construction companies blame Treasury rules for budgeting, which force the Highways Agency to include a margin of error of up to 45 per cent.

The rules were introduced to try to secure realistic prices for projects, but contractors say that they have contributed to the delays. Some companies believe that the Government does not want to admit that some schemes may never be realised.

A Highways Agency spokesman said that the Government was committed to the programme of improvements and that all the roads would be built. The agency said that it was working with contractors to reduce costs. Where that was not possible, increases would be met from a special reserve.

But the Highways Agency website says that progress on some schemes is “subject to the availability of funds”.

The National Audit Office has begun an investigation into the road-building programme but is not expected to report until 2007.

Supporters of trams and light rail have seized on the cost overruns on road projects as evidence that the Government applied strict funding criteria to trams that do not apply to roads. Alistair Darling, Transport Secretary, withdrew £500 million in funding late last year from three tram projects.