(Reuters) - Public transportation workers in Philadelphia went on strike at midnight on Monday after they were unable to reach a contract agreement with the transit system that provides almost one million rides a day in and around the fifth largest U.S. city.

Some 4,700 workers represented by the Transport Workers Union Local 234 went on strike after their contract with Southeastern Pennsylvania Transportation Authority (SEPTA) expired, the transit system said in a statement.

RELATED: Your complete guide to navigating the city during the strike

The strike will shut down bus and most trolley routes in Philadelphia, leaving hundreds of thousands of workers and students to find different ways to get to their jobs and schools on Tuesday.

"We ask everyone to be prepared for very crowded trains and travel inconveniences," SEPTA said on its website.

The School District of Philadelphia said late on Monday night that all of its schools would remain open and students and employees were expected to report to work and school on Tuesday.

About 60,000 public, private and charter school students use the public transportation system each day, local media reported.

The contract expired at midnight on Monday after union members and system officials were unable to reach an agreement over health care benefits, pensions and issues involving worker conditions, local media reported.

The strike drew concerns from city officials over what interrupted public transit could potentially mean for voters on Election Day when they go to the polls next Tuesday to elect the next U.S. president.

“We’ve always had difficulty, on a good day, to be able to have enough support to move people to polling places,” City Council President Darrell Clarke told PhillyVoice.com. “So if there is not public transportation we will clearly have a problem.”