New park-and-ride sites in Witney, Bicester and Abingdon are being examined as part of a multi-million pound investment in Oxfordshire's public transport.

Car use and traffic jams on the county's main roads are becoming such a problem that Oxfordshire County Council has commissioned a study to look at the possibility of building three new satellite park-and-rides to ferry people in and out of Oxford.

Although no sites have yet been identified the idea is to have a countywide public transport infrastructure the envy of the UK in place by 2010 the time Oxford's Westgate project is due to open.

And with proposed increases in patrolled on-street car parking particularly in and around Headington additional park-and-ride capacity is seen as vital.

There are currently five park-and-ride sites in the county, all of which surround Oxford.

Thornhill and Water Eaton are run by the county council while Seacourt, Redbridge and Pear Tree are run by Oxford City Council.

In a report to county councillors, the authority's sustainable transport manager, Noel Newson, said: "Use of the Thornhill and Water Eaton car parks has been growing steadily, with the former often operating close to capacity for much of the week.

"Use of Pear Tree and Seacourt has been fairly stable, but they are close to capacity at time of high demand.

"There has been a fall in use of the Redbridge car park, which in part reflects the growth in use of local bus services between Abingdon and Oxford."

Since park-and-ride was first introduced in Oxford in 1992, the average weekly use has increased from 22,990 to a figure of 28,055 last year.

And with the Highways Agency stating the clogged-up A34 will receive no new investment until 2016 at the earliest, a realisation has dawned that something needs to be done.

County councillor and Witney resident David Robertson, cabinet member for transport, said: "Certainly Bicester and Witney are being looked at.

"Witney is getting to the stage where a local park-and-ride would benefit people travelling to Oxford instead of driving miles to use one. We have got to make things useable for people and encourage them to leave their car.

"You will never force people out of cars simply because they have the comfort, but park-and-ride has been fantastic for Oxford and now we are moving on to look at a different strategy."

Although £8m has been earmarked for park-and-ride expansion, money would also be gained from developer contributions and on-street parking surpluses.

Barry Norton, the leader of West Oxfordshire District Council, said: "There is absolutely no doubt an edge-of-town site would tick a lot of boxes.

"It would really help with persuading those who drive in to Oxford to leave their cars and catch a bus. Anything that helps relieve congestion on the A40 we would welcome with open arms.

"A park-and-ride might even provide us with the opportunity for a lorry park, so it makes a lot of sense."