The two people, whose names were not immediately released, suffered serious leg injuries and were taken by helicopters to Allegheny General Hospital, Pittsburgh, state police said.
Police closed the southbound lanes in North Strabane Township between the Racetrack Road and Houston exits for several hours while troopers investigated the crash.
Police began pursuing the motorcycle shortly before noon near the Carnegie exit in Allegheny County when a trooper there attempted to stop the vehicle for speeding at 105 mph, said state police Cpl. Barry Gaston. Three state police cruisers from the Moon Township barracks followed the motorcyclist south into Washington County until other police cars attempted a rolling roadblock ahead of the motorcycle to slow it down near the Racetrack Road exit.
The driver instead turned around on the interstate and began driving in the wrong direction, Gaston said. The motorcyclist missed the first cruiser, but crashed into a second police car, which sustained damage near the driver's side bumper.
The motorcycle driver and passenger were thrown into the grassy median. Both were wearing helmets at the time of the crash. Their conditions were not immediately known Friday.
None of the troopers involved in the chase was injured, said Capt. Sheldon Epstein, the commanding officer of Troop B in Washington.
J.T. Himmelrick said he was working at the McDonald's restaurant on Racetrack Road when a state constable he knows came in with a hand-held police scanner that started squawking.
Himmelrick said he saw two or three police cruisers attempting to barricade the road. When he and the constable were able to get outside to the parking lot, the sounds of crunching metal and sirens reached a crescendo.
"By the time I looked up, you could just hear cruisers and sirens coming through there," Himmelrick said. "Everything just seemed to happen at once."
Within minutes, troopers had surrounded the scene, he said.
A reporter responded to the scene but was ordered to leave the crash site by a state trooper on motorcycle. The reporter subsequently was issued a citation for parking on the highway.
State police earlier this month released a report on police pursuits statewide, which dropped slightly in 2008.
According to the report, police departments across Pennsylvania were involved in 1,809 that year, down from 1,931 in 2007. However, police pursuits involving motorcycles increased from 184 in 2007 to 201 last year.
Nine people died in pursuit-related crashes in 2008.
Staff writer Amanda Gillooly contributed to this story.