TRANSPORT chiefs have drawn up rules allowing a city-centre bridge in York to be shut for 18 months - but say the outcome of a controversial six-month trial closure is not a done deal.

Lendal Bridge will be closed to cars and motorbikes between 10.30am and 5pm every day from August 27 to next February, with the Labour-controlled authority saying it hopes the move will speed up bus times, cut pollution and encourage more people to walk, cycle and use public transport.

City-centre businesses, backed by the York and North Yorkshire Chamber of Commerce, have said the scheme will damage their trade and opposition parties claim it will cause congestion chaos in other parts of York.

The council has now published an “experimental traffic order” designating the bridge as a “local bus lane” from next Tuesday to February 26, 2015, a year after the trial ends and its impact is assessed.

Conservative councillor Chris Steward said: “It seems everything is pointing in the direction of extending this closure rather than reducing the trial if it is not working after two or three months, and that minds are made up without even knowing the criteria by which the success of this trial will be judged.

“People need to know how it will be monitored and what arrangements are in place for calling it off if it is not working. There have been no answers about precisely what the council wants to achieve and how success will be measured, and nothing to say that it wants, for example, bus passenger numbers or city-centre footfall up by a certain amount. The outcome of this trial increasingly seems pre-decided”.

Darren Richardson, the council’s director of city and environmental services, said: “Temporary traffic restriction orders [TROs] allow implementation for up to 18 months, but the trial will be for a six-month period.

“After six months, should the decision be taken to extend the trial following a planned review of learning from the trial, the TRO in place means the council will not have to apply for a new order and therefore not incur the extra cost associated with this.”

Coun Dave Merrett, cabinet member for transport, said: “Officers have been working with the independent Institute of Transport Studies at the University of Leeds on developing and finalising a set of monitoring criteria which will be used in assessing the Lendal Bridge trial.

“The report on this is due this week and will be made public so everybody can see how the trial will be measured and evaluated.”