OXFORD’S busiest park-and-ride site is set to be expanded by more than 500 spaces because it is “swamped” with motorists.

Oxfordshire County Council officers have recommended another 540 spaces are added to the 850-vehicle Thornhill site following investigations into how many motorists use the car park.

If councillors back the idea, a planning application for scheme, which would cost between £3m and £4m, could be submitted in the spring.

Councillors will also be asked to consider introducing an as-yet unspecified charge for drivers who use the car park to travel to London and to airports, to protect the “core use of the site” – allowing motorists to use it for access to Oxford.

The idea will be put to the council’s transport decisions committee on Thursday, January 7. County council spokesman Paul Smith said: “Anyone who regularly uses Thornhill will tell you there is clearly a need for more parking spaces.

“Thornhill is unique among Oxford’s park-and-ride sites in terms of the high demand for travel into London, and while this has become an important feature of the site, our priority remains to protect core use for travel into Oxford at all park-and-ride sites.

“As such we feel that introducing a small fee for motorists travelling to other destinations represents the most viable option.

“It is not clear at this stage exactly how that charging system would work or what the costs would be.

“But it makes sense for our officers to start looking into this in addition to preparing a planning application.”

Charges at all five of the city’s park-and-rides were scrapped in 2008 when County Hall took over the running of the sites.

A report to councillors said while there is increasing demand at all five park-and-ride sites, Thornhill experiences by far the greatest pressure, with the car park filling up to capacity almost every weekday by about 9.30am.

Officers said there was currently a high unmet demand, which would rise to a need for more than 500 parking spaces by 2026.

Oxford Civic Society has been pressing for an expansion of Thornhill for years and its chairman, Tony Joyce, welcomed the news.

He said: “We are absolutely delighted that the county council is able now to move ahead in increasing Thornhill’s capacity.

“The demand for this has been obvious for some time.

“The park-and-ride system was originally planned to meet the needs of those wanting to visit Oxford.

“It is important that this function can been maintained.

“Clearly, in recent years, Thornhill has been swamped by those wishing to use it to travel to London and the airports.

“It has seriously lost its proper first function.

“It is of such use to travellers that a reasonable charge for those wishing to use it for other purposes seems entirely reasonable.”

Mr Joyce said having a permanently full park-and-ride meant it was not able to adequately serve patients wanting to reach Oxford’s main hospitals in Headington or people who worked in the area.