MARC service was halted from about 2:30 p.m. until shortly after 5 p.m. along the Penn Line and Amtrak service was shut down from Washington all the way to Philadelphia, said Craig Schulz, an Amtrak spokesman.
"Just because of the volume of trains, we're getting full in Baltimore and there's no where to go in Wilmington, so we're holding in Philadelphia where we have more room," Schulz said.
The service resumed just after 5 p.m. but at reduced speeds, he said, and passengers were told to expect "congestion-related delays."
"Obviously we're aware of the fact that its 4:30 on a Friday with high passenger loads," he said amid the shutdown. "We're at the mercy of the local authorities at this point. As soon as they say we can go, we'll go, but at this point we're hamstrung."
The Maryland Transit Administration said the incident occurred at 2:27 p.m. Prince George's County police said they were first dispatched to the 2000 block of Kenilworth Avenue in Capital Heights about 2:40 p.m.
Cpl. Nate Lewis, a police spokesman, said detectives were investigating why the man was on the tracks.
Assistant Chief Paul Gomez, of the Prince George's County Fire and EMS Department, said emergency personnel and police were called to Olive and S streets, south of the Cheverly Metro Station, for a report of a struck pedestrian.
The location is near the state line with Washington, south of where Kenilworth Avenue, Route 295 and Route 50 meet.
The Maryland Transit Administration reported about 3:25 p.m. that all Penn Line MARC service was suspended. About two hours later, at 5:25 p.m., the service was just beginning to resume.
"We are starting to move at significantly reduced speeds," said Paul Shepard, a MTA spokesman.