A £2m plan to improve Oxford's busiest roundabout will attract more traffic, transport planners have admitted.

Yesterday, the county council's executive board approved plans for the "Hamburger", a redesign of the Green Road roundabout in Headington, the county's biggest accident blackspot. A £40m flyover has been ruled out.

Eddie Luck, assistant director of transport development, told the committee that the traffic lights, and the hamburger design, a new lane through the middle for A40 traffic from London to Kidlington, would make the junction safer to use and easier to access.

He said there was a strong possibility that traffic flows would increase once the changes were made, because so many cars avoid the roundabout at the moment, choosing instead to use other routes or local rat-runs.

Mr Luck said: "I'm sure we'll see some growth in traffic as we improve it.

"People will no longer rat-run through Wheatley and other places."

The plan, which could be completed by February 2005, following public consultation, should help to reduce the accident rate.

There are 6,000 vehicles using the junction in peak hours, with one accident a month over the past three years, although none of them have been fatal.

Margaret Godden, the council's deputy leader, said she did not understand how the roundabout would work, but accepted the highway officers' recommendation.

She added: "I hang on to my seat when I'm driven around the roundabout now, but the hamburger design looks even more terrifying."

Several measures will also be taken to give buses more priority in an area which is on the route to Thornhill park-and-ride.

These will include:

The provision of a bus lane on the A420 London Road eastbound to reduce delays for buses leaving Oxford centre.

Traffic signals at the junction of Bayswater Road and Waynflete Road with priority for buses leaving these routes.

Giving buses traffic signal priority on the A40 westbound on the approach to the roundabout.

David Robertson, the council's executive member for transport, added: "This innovative scheme will reduce congestion and accidents as well as giving us the chance to give buses priority in the area."

Sylvia Tompkins, a county councillor for Headington, hoped the new measures would also reduce congestion on North Way, which leads to the roundabout from Barton.