PITTSBURGH — About 2,200 bus and trolley drivers, mechanics and clerks say they'll stop working Dec. 1 if the Pittsburgh area's transit agency imposes a new contract on them that day.

The Port Authority of Allegheny County Board last month voted to approve the new contract after declaring an impasse with its union.

If the drivers walk out, they'll strand customers who take about 230,000 rides a day.

The Port Authority says the new deal includes 3 percent annual raises. It also raises the cost of health care and retirement age for its employees.