Flagship M1 car-sharing lane is brought to a standstill before it even opens due to safety fears

The High Occupancy Vehicle lane was to have been used by motorists carrying at least one passenger.

The lane - the first in Britain - would have occupied the outside of the M1 between St Albans and Luton.

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Scrapped: Work goes on to widen the M1 between St Albans and Luton and make room for a High Occupancy Vehicle lane, which has now been ruled impractical

The motorway is being resurfaced and widened from three lanes to four each way to make room for the HOV lane and improve flow.

The showpiece government scheme was meant to encourage car sharing and let multiple-occupancy cars speed past slower ones. It was to open in December this year.

But despite being heavily championed by ministers as a solution to congestion it has been quietly scrapped.

It has reportedly been ruled out as impractical and dangerous by the government's own advisers.

A study has warned it would make motorists crash as they swerved around slow-moving drivers on the road ahead. It also said the scheme was virtually impossible to police.

The death knell was sounded in a feasibility study - put on the internet by Transport Secretary Ruth Kelly as she announced her blueprint for a network of toll and car-share lanes this week.

It warned that if the HOV lane was in the outside lane of the motorway it would trigger crashes as drivers - frustrated by slow-moving cars ahead - swerved into inside lanes to "undertake".

It also said there were no refuge areas next to the outside lane for broken-down vehicles.

Moving the scheme to the inside lane was dangerous too - it would force drivers to cut across the HOV lane to leave the motorway.

The study warned there were "limited opportunities" for HOV lanes elsewhere. It said there were currently no cameras available to enforce the scheme which would rely entirely on the police.

But it would be dangerous for police to stop lawbreaking drivers in the outside lane.

Edmund King, AA president, said: "This proposal was the most important and radical car-share lane planned by the Government - it was their flagship. Now it's been ruled totally impractical and unsafe.

"These are problems already well known in the US where they call it the 'snail effect' - drivers sitting in their pickup trucks at slow speed in the HOV lane and holding everyone else up."

The AA said the only solution was to build a second HOV lane for undertaking but that this was prohibitively expensive.

The Department for Transport confirmed that the M1 HOV lane had been scrapped. It was "not the right solution for this particular location".

The M1 would now have variable speed controls similar to those on the M25 to "maximise traffic flows and improve safety" instead.

This week Miss Kelly also envisaged opening up hard shoulders on motorways, possibly allowing motorists who pay extra to use them.