A man who was walking in a southbound travel lane of Interstate-95 in Bucks County was killed about 3 a.m. Saturday when he was struck by an SUV, the Pennsylvania State Police said.

It was not immediately clear why the man was walking on the highway, just south of the Street Road exit (Exit 37). Police have not yet released his identity.

Part of I-95 South was closed, from Street Road to Woodhaven Road (Exit 35) for more than four hours, from 3 a.m. to 7:45 a.m., when vehicles were detoured off from Street Road. Traffic is now back to normal, police said.

The male driver of the SUV stopped at the scene and has been cooperating with investigators, police said. No charges were pending against him.