The train hit the man about 4:15 p.m. as he was working on the power lines on the inactive trolley tracks near the station at 22nd and Market streets, said Jerri Williams, a SEPTA spokeswoman.
The trolley lines have been closed in recent days as the transit authority completes its renovation of the tunnels serving them.
Williams said that the worker was part of a full crew of laborers working to finish that project ahead of its deadline next week.
The worker "misjudged the distance" between the active tracks of the El and the trolley tracks, Williams said.
As he was leaning into the El track area, his back was hit by the passing train, which dragged him several feet before stopping.
"Our main concern now is the investigation," she said. "With an employee injured like this, it's very important that we find out exactly what happened."
Part of that probe will include reviewing footage from nearby security cameras, and ensuring that all signals and other equipment were in working order at the time, Williams said.
Service on the El was suspended for about an hour after the incident, Williams said.
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