Cutting journey times along the A12 by just one minute would cost at least £10 million, an inquiry heard yesterday.

The opening day of the independent A12 inquiry, chaired by former Department of Transport permanent secretary Sir David Rowlands, also heard that schemes such as introducing average speed cameras or banning heavy goods vehicles from overtaking could be introduced in the next few years.

But the hearing, at county hall in Chelmsford, was told that, even if the process towards the much-mooted widening of the entire Essex stretch to three lanes started today, work would not begin until at least 2017.

Tony Ciaburro, Essex County Council's director for development, highways and transportation, told the inquiry that traffic management could help keep cars moving at rush hours and reduce the number of accidents.

He said a short-term package of measures could include introducing average speed limits of 70mph, or possibly lower or variable speed limits along the most dangerous stretches, such as between Kelvedon and Hatfield Peverel.

"People are driving too fast and too close to each other, particularly in adverse weather conditions," he said.

"There are sections of the road where it would certainly be worth looking at whether a lower speed limit would be appropriate."

Other forthcoming changes could see the introduction of real-time information screens, allowing people to see how much congestion there is on the road.

But Mr Ciaburro warned road improvements would not be cheap.

"I wouldn't be surprised if it would be in excess of £10 million a minute," he said.

"If you want to cut journey time reliability by a minute on this road, you would have to do something substantial to improve the journey time."

Earlier, county council cabinet member for transportation Norman Hume, and his predecessor, Rodney Bass, told the inquiry that, although regional bodies in the East of England had been given responsibility to pay for any upgrades to the road, the hundreds of millions of pounds needed to carry out the work was simply not available.

The second day of the three-day inquiry will take place on May 1.