Oxford looks set to be swamped with travelling pensioners when a free, national bus service starts in April.

The much-anticipated concessionary bus scheme - one of Gordon Brown's so-called "Brown's Bonuses", delivered in a budget when he was Chancellor - was said to herald a new era in bus travel for those aged 60 and over.

But for administrators, it has been a number-crunch- ing nightmare.

From April 1, pensioners will be able to travel where they like within England and Wales - and for the first time, totally free.

The scheme entitles those eligible to travel for free on local service buses, not operators like National Express.

The scheme is paid for by local authorities, with the councils in towns or cities to which OAPs have travelled picking up the cost for their journey home.

In truth, no one is exactly sure how much the scheme will cost to run - but it has concerned Oxford City Council so much some have estimated it could cost more than £3m-a-year.

And if many more people come to Oxford than expected, it could have serious implications on future budget plans.

Graham Smith, Oxford City Council's transport and parking manager, said: "Oxford is going to be swamped with journeys, that's for sure.

"But the only way of sorting (the cost of the scheme) out is to get the Government to pay for it, that way there is no problem - and that is what a lot of people think should have been done. If it goes completely wrong and we have a huge take up then I don't know what will happen, but until April arrives it's an unknown. New nationally-recognised passes to existing holders will be issued from February - pensioners don't have to reapply."

OAPs used to pay a reduced rate for bus travel, but it is currently free within local authority boundaries.

Confusion has reigned over free bus travel schemes since it was first ann- ounced.

Oxford's two main bus companies - Stagecoach and the Oxford Bus Company - lodged an appeal with the Department for Transport about proposals the city council put forward to reimburse them.

Oxford pensioner's spokesman Bill Jupp said: "I just can't see there is going to be much change from how it is now, because it would be too traumatic to travel across the country.

"Pensioners are not the kind of people who want to move about.

"But free travel within local authority boundaries has been great because it has enhanced people's lives and allowed people to get out of their homes."

Oxford Bus Company director Louisa Weeks said: "It's too early to predict what effect the changes will have, but we will respond to any increase in demand.

"Already, 50 per cent of journeys into the centre of Oxford are by bus and an increase in visitors will bring even more success to the city centre economy."

No one from Stagecoach was available for comment.