(AP) -- Transit workers in Philadelphia are hitting the picket lines Tuesday and commuters are scrambling to make alternate plans after the city's main transit agency and a union representing about 4,700 workers failed to reach a contract agreement.

The union went on strike at 12:01 a.m. Tuesday, shutting down Southeastern Pennsylvania Transportation Authority buses, trolleys and subways that provide about 900,000 rides a day. The strike does not affect commuter rail lines and service in areas outside the city.

"Despite months of constructive and innovative proposals from our side of the table, management has refused to budge on key issues including safety issues that would save lives and not cost SEPTA a dime," said TWU Local 234 President Willie Brown, who heads the union's negotiating team. "There is no new agreement, so we are on strike."

Brown said union members will not report for their shifts at SEPTA, and will instead report for picket duty.

SEPTA expressed its disappointment in the decision in a statement released shortly after the strike was announced.

"The decision by TWU President Willie Brown leaves thousands of SEPTA customers without the transit services they rely on for travel to and from work, school and medical appointments," said SEPTA, adding that it remained "ready and willing" to continue bargaining.

Brown said the two sides remain far apart on pension and health care issues as well as noneconomic issues such as shift scheduling, break time and other measures that affect driver fatigue.

SEPTA said it is hopeful that a tentative agreement will be reached before Election Day.

"If we foresee an agreement will not come to pass, SEPTA intends to seek to enjoin the strike for November 8th to ensure that the strike does not prevent any voters from getting to the polls and exercising their right to vote," SEPTA said.

Businesses, hospitals and schools began preparing last week for a possible transit shutdown.

The strike will have a major impact on the Philadelphia school system, though it will remain open. SEPTA provides rides for nearly 60,000 public, private and charter school students.

Democratic Gov. Tom Wolf encouraged both sides early Tuesday to continue talking until an agreement is reached.

"Hundreds of thousands of Pennsylvania residents rely on SEPTA to travel each day to and from work and school and the inability of TWU and SEPTA to reach an agreement is devastating for many of these individuals and their families," Wolf said in a statement. "This will create extreme hardships for the city and for businesses."

Democratic Mayor Jim Kenney also urged SEPTA and the union to keep communicating despite the strike, and he urged residents to have patience.

In 2014, union members ratified a two-year contract that averted a threatened walkout. In 2009, a strike by SEPTA workers lasted six days.