OTTAWA (CBC) - The union representing Ottawa's transit workers says the city will have to hire more bus drivers in the next two years to make up for restrictions in its new three-year contract.

In a binding decision handed down in October, an arbitrator ruled that OC Transpo bus drivers can't work more than 13 hours a day.

Scheduling had been the main issue behind the 53-day strike last winter by 2,200 OC Transpo drivers, dispatchers and maintenance workers.

On Tuesday, André Cornellier, the president of Amalgamated Transit Union Local 279, told CBC News the new rules are so restrictive that the city may have to hire as many as 100 new drivers to cover its transit routes.

"Before, people would take that overtime and go out and do that work. Now that the new work-rest rules are coming in they are going to have more drivers to cover that work."

Cornellier predicts that hiring additional drivers will cost the city millions, but without them, he said, there could be cuts in service.

Ottawa city councillors who received a confidential briefing on the matter Tuesday by OC Transpo officials have conflicting views on how the city will handle scheduling.

Coun. Diane Holmes expects to see more drivers hired, as well as service cuts, while Coun. Marianne Wilkinson said hiring more drivers is not an option.

"We've been told by our staff that we are not in the need to hire people at this point," Wilkinson said. "It's not in our budget to do that."

OC Transpo cannot hire part-time workers because the arbitrator's decision guaranteed a minimum workday a driver must be paid 7.5 hours compensation per day for even one hour's work.