The incident was the second in two days to affect Regional Rail service at a time when commuter trains are coping with extra passengers because of the strike by SEPTA's largest union. SEPTA officials said the accident was not attributable to the strike.

Kevin Sparks, 34, of Sharon Hill, was struck about 8:30 a.m. by a southbound train near the Philadelphia-Montgomery County line just south of the Melrose Park station. He died at the scene.

Sparks, an eight-year SEPTA employee, was part of a team inspecting tracks that normally carry northbound trains. It was unclear yesterday how fast the train had been traveling.

SEPTA officials said trains often switch tracks because of equipment issues, said spokeswoman Jerri Williams.

"It's a set procedure," Williams said. "The people working on tracks know that's a possibility at all times and assume trains will be coming from either direction."

One of the passengers reported hearing the train's horns blaring before there was a loud bump.

The incident disrupted the Warminster (R2), West Trenton (R3) and Lansdale/Doylestown (R5) lines north of Fern Rock.

On Wednesday, a fire forced the evacuation of about 500 passengers from a train on the R5 Paoli line. No one was injured, but service on the line was suspended for two hours. Flames broke out in the first of four cars as the train was leaving the Overbrook station about 7 a.m. Passengers had already been moved to other cars because of a burning smell.