Megabus officials confirm the incident happened about 6 p.m. Monday near the Bedford exit as the bus was westbound from Philadelphia to Pittsburgh.
James Grantz, a pastor of the City Reach Church on Pittsburgh's North Side, told KDKA-TV he noticed the driver was incoherent and he grabbed the wheel. Passengers told reporters that two semis, whose drivers apparently noticed the bus was weaving, blocked the bus from going off the road until Grantz gained control of the vehicle.
"I said, 'Ma'am, you need to pull over,'" Grantz told KDKA, adding the driver didn't respond and seemed "out of it."
"She was still sitting on the seat. I kind of leaned on her and grabbed the wheel," Grantz said. "I felt the adrenaline. I was shaking."
Grantz said the driver told him she needed to change her eyeglasses and indicated she had forgotten her blood-pressure medicine. Another passenger, Stefon Braxton, confirmed that account.
Braxton said Grantz "jumped on her lap and started steering the bus, and the other passengers, they pulled her out." The driver mentioned her blood-pressure medicine when she regained consciousness.
"I think she thought she could make it to Pittsburgh to get her medication, but it just didn't work out that way," Braxton said.
Megabus officials said the driver has been checked by doctors and is doing well. A relief driver was brought in to complete the trip to Pittsburgh.
"Safety is our absolute priority and, as a matter of course, we are investigating the incident," Megabus said in a statement. "We apologize to Megabus.com passengers for the disruption to their trip."
Grantz didn't immediately return a message left by The Associated Press at his church Wednesday.