Philadelphia ? The union representing Philadelphia subway, trolley and bus workers walked out of contract talks Friday, days before a threatened strike that would leave hundreds of thousands of passengers to find alternate ways to travel.

The city is preparing for a possible strike on Monday by setting up extra bicycle racks and allowing more parking. City schools, which don’t provide bus service for high schoolers, plan to remain open, but could reconsider if there is a prolonged strike.

The last Philadelphia transit strike, in 1998, lasted 40 days.

The union, which represents 5,000 transit workers, has already authorized its leaders to call a strike if needed.