Members of Transport Workers Union Local 234 could hit the picket line as soon as Friday if no deal is reached by then.
They voted last month to authorize a strike.
SEPTA said Wednesday that it expects negotiations to continue through Thursday.
The contract expires at 11:59 p.m. Thursday. SEPTA said it is not yet definite that the union will strike, saying that the decision will be up to union leaders.
SEPTA spokesperson Andrew Busch said that if the union does call a strike, it would shut down all bus, trolley and subway/el service within the City of Philadelphia.
Regional Rail would run into the city as normal, and the suburban transit services - buses, Routes 101 and 102 trolleys, Norristown High Speed Line - would operate.
SEPTA has released a guide with travel times for riders in the event of a strike. That guide is posted here at SEPTA.org.
After the strike authorization vote last month, union representatives said they are fighting for more pay and improved safety and security.
Members of the union said in October that ongoing violence around the city is becoming a major problem for them.
"Seems as though we are not as important as they like to say we are because if they were, safety would be paramount," said Andre Jones Sr., vice president of TWU Local 234, said at the time.
School District of Philadelphia planning for possible SEPTA strike
The School District of Philadelphia said it is making plans in the event a SEPTA strike starts Friday.
A strike would impact 55,000 students who commute on city bus and metro services, officials said.
The district released the following list of considerations in the event of a strike.
- The District is closely monitoring staffing levels and will deploy Central Office staffing support, as needed.
- In cases where student or staff attendance is dramatically affected by the strike, the District may recommend that a school move to virtual instruction.
- In such a case, District and school leadership will ensure that all students, including and especially those with special needs, are equipped with the digital and physical materials they need to participate in virtual learning. Teachers will not deliver in-person and virtual instruction at the same time.
- Students who are late or absent due to SEPTA-related travel challenges will not be marked late, or will be excused upon receipt of a note from the parent or guardian.
- Staff late arrivals due to SEPTA-related travel challenges will be recorded as excused.
- The District is committed to maintaining vital support for students and families such as technology services, safety and more.
School district officials will release another update on the situation Thursday.