Belfast taxi drivers are campaigning to be allowed to use bus lanes on a permanent basis, citing improved traffic during a three-month trial, the Belfast Telegraph reports.

The 12-week trial allowing taxi drivers to use the bus lanes to bypass traffic in the Northern Ireland city kicked off on Feb. 20. Taxi companies say the transition was smooth, and that they already see benefits in terms of quicker traffic and reduced congestion.

The owner of one of Belfast’s biggest taxi companies, Fona Cab, says allowing taxis to use bus lanes helps customers reached their destination quicker and more cheaply, and allows drivers to complete more journeys each day. The owner, William McCausland, also says taxis provide an important transportation service for people who are physically unable to go stand at a bus stop, like some customers who need to get to hospital appointments.

Detractors of the move decry McCausland’s assertion that taxis provide “a vital public service,” and say that allowing taxis into bus lanes will, in the long run, slow down buses and cyclists. Cycling advocate Jonathan Hobbs of bikefast.org says the brief trial is being used to gather one-sided evidence to support the switch.

“A decade of departmental research says allowing private taxis to have the run of bus lanes will have long-term negative effects, he says. “The trial will have to show something amazing to shift that position.”

Bikefast released a “survival guide” for cyclists for the 84-day trial, urging cyclists to not stay off the road during the trial and to report all collisions and dangerous incidents to make sure the trial does not become permanent.

A sustainable transportation charity, Sustrans, also released a statement against making the move permanent:

We all know that taxis are private hire vehicles which are not a substitute for an efficient public transport system. The purpose of bus lanes is to provide sustainable transport corridors to improve the efficiency of moving people around an urban area, while reducing congestion and air pollution. Belfast simply cannot support the predominance of private vehicles on our road, including taxis.

Once the trial wraps up on May 14, the city’s Department of Infrastructure will assess the impact of the change on traffic and bus times before deciding whether the change will be permanent.