Philadelphia-area transit workers have voted overwhelmingly to ratify a two-year contract with the local transportation agency, averting a strike that threatened to cripple bus and rail lines and that their union warned would be long and contentious.

The contract, which puts off a final resolution on pension reform and medical benefits, was approved by about three-quarters of members of Transport Workers Union Local 234 who took part in the ratification vote on Friday, according to figures on the union's website.

Leaders of the local union had warned a strike would begin on Monday if the agreement, which they had urged members to approve, was not ratified.

The local represents about 5,000 bus, trolley and subway operators as well as mechanics and maintenance workers, and is the Southeastern Pennsylvania Transportation Authority's largest labor group, Jerri Williams, a spokeswoman for the agency, said on Saturday.

Under the transportation authority's collective bargaining system, the financial terms of the agreement with its largest union apply to the rest of the agency's workers, she said.

The agreement between the transportation agency and Transport Workers Union Local 234 provides a 5 percent pay hike over two years and a one-time "pension bonus" of $175 per year of service for any worker who retires in the next two years.

During the contract, the union and the transportation authority will negotiate over how to restructure pension plans and over medical benefits, because those issues were deemed too complex to address at this time, according to a union newsletter on the organization's website.

The newsletter, which went out last Monday, had warned members that a strike would "be a long and difficult one" if they did not ratify the contract on Friday.

A representative from the union could not be reached for comment on Saturday.

The Southeastern Pennsylvania Transportation Authority, which has an annual operating budget of $1.3 billion, is the sixth-largest transit agency in the United States, serving nearly 360 million riders a year, according to a report last year from the American Public Transportation Association.

The average pay of an operator for the Philadelphia-area agency is about $60,000 a year with overtime, Williams said.