SPEEDS on the northbound A34 west of Oxford will be reduced to improve safety.

The 50mph speed limit zone, which currently ends just north of the Botley interchange, will be extended north for half-a-mile, towards the Wytham slip road.

A number of other changes will be made as part of a seven-week long programme of work, which will start on Monday.

Road markings and signs will be altered and the cycle lane on the slip road from the roundabout will be improved.

An anti-skid surface will be laid on the northbound slip road on to the A34 and a layby alongside the northbound carriageway will be removed.

The Highways Agency said that the slip road was an “accident cluster”, with most incidents involving cars joining the A34.

Safety problems occur because vehicles using the slip road from the interchange roundabout are joining the A34 at the same point where traffic already on the northbound carriageway starts to speed up, because drivers see the signs marking the end of the 50mph zone.

Extending the zone further north will stop traffic accelerating and improve safety, according to traffic engineers who surveyed the area.

Highways Agency spokes-man James Wright said: “It’s not that the accident rate is high at this location, it’s just there have been a number in a relatively small area.

“There were a number of incidents caused when vehicles were entering the A34 from the slip road.”

The alterations will be carried out overnight, with lane closures to create a safe area for the workmen.

The slip road will be closed overnight for two nights but the dates for the closures have yet to be fixed.

Project manager Surinder Bhangu said: “We have planned this work carefully to keep disruption to an absolute minimum, and will be carrying out all our work overnight, when traffic flows are lowest.”

The work follows the installation of “smart” traffic lights at the interchange last summer, along with pedestrian and cycle crossings on the A420 dual carriageway.

Last month, the interchange’s northbound exit slip road was resurfaced.

Ian Hudspeth, Oxfordshire County Council’s cabinet member for infrastructure, said that the lower speed limit could improve journey times.

He said: “During the Wolvercote viaduct roadworks there was a reduced speed limit that was not detrimental to traffic flow.”

Mr Hudspeth said it was better to carry out work in one go but said he understood that funding for various projects was not also made available at the same time.