That's because all roads leading to the eastbound lanes of the bridge have been shut down, the Delaware River Port Authority said Tuesday afternoon.
The closures include the ramp from the Vine Street Expressway (I-676) eastbound to the bridge.
Drivers are urged to take either the Walt Whitman Bridge or the Betsy Ross Bridge for travel to New Jersey.
The westbound lanes of the Ben Franklin Bridge, from New Jersey into Philadelphia, remain open.
The debate between fmr. President Donald Trump and Vice President Kamala Harris will be held at the National Constitution Center.
Coverage begins at 8 p.m. on 6abc. The debate starts at 9 p.m.
More Philadelphia Street Closures and Traffic Impacts for Presidential Debate
There will be closures for vehicular and pedestrian traffic, mass transit detours, and possible rolling street closures related to the event.
The following details were released by the city:
Tuesday, September 10 - Wednesday, September 11
Street closures are in effect from Arch to Market Streets, between 4th and 7th Streets.
Vehicular and pedestrian traffic will be allowed on 4th Street and Market Street.
No one will be permitted inside those secure closure points. Arch and Race Streets will remain closed throughout the duration of the event.
The 6th Street exit of I-676 eastbound is also closed. I-676 westbound is expected to remain open but may close if necessary.
Closures will remain in effect until the event area is cleared, which is expected Wednesday.
Employees who work inside the secure zone should access their building through an entry point at 7th and Arch Streets.
Public Transit
Due to road closures, several SEPTA bus routes will be detoured from their normal routes early Tuesday morning through Wednesday morning.
Buses will not stop at Market St. stops from 5th to 7th Streets in both directions due to fencing blocking the sidewalks.
The Market-Frankford Line will stop at the 5th Street Station, but only on the east side; the west side will be closed. SEPTA personnel will be on location all day to direct riders and monitor crowds.
SEPTA recommends visiting septa.org and following @SEPTA for the most up-to-date information as additional detours may occur due to unscheduled road closures.
PATCO train service will not be impacted by the road closures.
Stay Updated
Road closures, reopening, and other information related to the debate will be published on the Philadelphia Office of Emergency Management, City of Philadelphia, and the Philadelphia Police Department's social media pages. People can also sign up for free ReadyPhiladelphia alerts by texting READYPHILA to 888-777.