Make motorway limit 80mph to cut jams, Ministers told

Motorists would benefit most if traffic travelled at a 'target speed' of 78mph, it said.

This would enable quicker journeys, without seriously jeopardising safety.

The report by the Highways Agency examined the overall costs and economic benefits of travelling at speeds of between 30mph and 100mph - taking account of time at the wheel, fuel burned and accidents.

It concluded that 78mph was the most economical and 'appropriate' average speed, despite a rise in fuel consumption and more 'costly' crashes when vehicles travel faster than the current 70mph limit.

Similar calculations were also conducted for dual carriageways, where the most beneficial speed was found to be 71mph.

But traffic on single carriageway trunk roads was found to be most efficient at 54mph - 6mph lower than the present 60mph limit.

The report said: "At these targets, the network would operate in a balanced, safe, reliable and economic way to benefit society and users."

However, the Highways Agency report stopped short of recommending the changes, due to associated rises in exhaust emissions from vehicles travelling faster.

Congestion is estimated to cost British industry £15 billion annually.

The report revealed that an accident typically causes an hour's delay for 1,300 vehicles at a cost of £12,280 in fuel, missed appointments and time catching up - around £10 each.

The report, entitled "Development of a speed limit strategy for the Highways Agency" was carried out by the Government's former transport research laboratory, TRL.

It was commissioned by the Highways Agency, which manages local speed limits.

A complicated calculation established the average cost per kilometre based on hours spent at the wheel, the price of fuel on the journey and the cost of accidents in terms of vehicle damage, delays and injuries.

Quicker journeys 'would benefit individuals and businesses', it found but there would be some trade-off in accident costs.

The Department for Transport, which sets national limits, said it will be studying the report.

A DfT spokesperson said: "There are no current plans to change national speed limits but the department will look at the findings of the report."

Last night the Association of British Drivers said the current limit was no longer viable, and called for a rise to 80mph.

"This archaic 70mph limit has been with us for over 40 years and is well past its sell-by date,' said ABD policy adviser Nigel Humphries.