A BUS passenger group has called on operators to expand a landmark joint ticketing system in Oxford as they mark its fifth year.

The first of its kind in the UK, the Oxford SmartZone was introduced in July 2011 to make bus travel around the city simpler, cheaper and greener.

It saw Stagecoach Oxfordshire, Oxford Bus Company and Thames Travel agree to accept each other's tickets within a certain area and coordinate timetables, effectively creating one major bus network.

The zone's routes go out as far as Kidlington, Begbroke, Wheatley, Kennington and Cumnor but now Bus Users Oxford is calling on the firms to roll it out across the rest of the county.

Chairman Hugh Jaeger said: "In Oxford the SmartZone has led to quicker and more flexible services for passengers, who can catch whichever bus comes first.

"With the county council's cuts to bus subsidies, we may see usage of buses drop in some areas but joint ticketing might boost the number of passengers

"The SmartZone has been such as a success that we would now encourage operators to extend it to the rest of Oxfordshire."

Martin Sutton, managing director of Stagecoach Oxfordshire, said firms were "looking what future developments might be" but stopped short of saying the system would expand.

He also said a new operator was expected to join in the coming months but this had not been confirmed yet.

Mr Sutton added: "It has been a fantastically popular scheme, we are seeing passengers using buses much more frequently.

"What people wanted was a ticket that enabled them to get on the first bus that arrived and that is exactly what the smart zone allows them to do."

The SmartZone was the first of its kind to use powers under the Local Transport Act 2008, which relaxed competition laws and allowed councils and bus operators to work more closely together.

It has also taken hundreds of buses off city centre roads, through a combination of double-decker buses being used and joined-up scheduling between companies.

Mr Sutton said an example was services coming from Blackbird Leys. There were originally 24 buses per hour – 12 each via Stagecoach and Oxford Bus Company – but there were now 15 with twice the capacity.

Since the SmartZone has been introduced, he said passenger numbers had increased by about five per cent every year.

Oxford Bus Company managing director Phil Southall added: "We’ve achieved this without the need for a complex revenue allocation system which means administration savings are passed onto our customers keeping prices close to that of individual operator tickets."

And Ian Hudspeth, leader of Oxfordshire County Council, said: "The county council has always been very keen to encourage bus use and make it as easy as possible for people to get where they are going by public transport.

"SmartZone has done this very well and I am delighted to see it reach its fifth birthday."