Sir - In the last fortnight there has been a significant tariff change at Oxford station car park.

Bona fide rail passengers need only pay £4.50 for a day's parking via a mobile phone-based service, which they should only use once they get into the station proper.

Other motorists arriving before 10am will however find that they need to pay £20 for a day's parking. This change is in support of the city's strategy to deter unnecessary car use and to bring the station car park into line with other Oxford parking facilities. The benefit to individual rail travellers is, of course, that the car park is freed up for their use.

This change is a significant one, which is why the mobile phone service, RingGo, has already been available for a month, supported by signage and leaflets handed to arriving motorists. I do apologise to anyone who wasn't made aware of the service through this publicity.

RingGo is itself not new. It has been available at over 60 FGW stations for over a year now, and similar special pricing for rail travellers was introduced at Bristol Parkway over two years ago.

The Oxford implementation was a carefully orchestrated change but we accept things can always be clearer.

For those planning to park and travel from Oxford station in future may I suggest three things to your readers: i) Register your details in advance on the web at www.RingGo.co.uk - this will assist and greatly speed first-time use.

ii) Please do ensure you have a charged mobile phone with you when you travel.

iii) If in any doubt, there are explanatory leaflets available at the booking office, and staff fully briefed at the information desk.

Most motorists are finding RingGo convenient and easy to use. Be assured we are intent on making that the overwhelming majority.

Harry Clarke, Commercial director, RingGo