Commuters experienced major delays during Wednesday morning’s rush hour on Metro’s Red Line, the busiest in the system, because of a track hazard near the Judiciary Square station.

An inspection vehicle known as a Sperry car detected a problem about 3 a.m., when the system was closed to passengers.

A switch point, which helps determine which direction a train will go, was found to be “flawed,” Metro spokesman Dan Stessel said.

Repair crews arrived at the scene with equipment by 5 a.m. and began working to replace the switch point and parts of the rail.

But it took three hours for the work to be completed and the track area to be tested.

Passengers on the Red Line at the Forest Glen station head toward downtown in April 2011. Metro riders on the red line experienced delays Wednesday morning because of a switch problem near Judiciary Square. (Michael S. Williamson/THE WASHINGTON POST)

In the meantime, trains on the Red Line had to single-track between Union Station and Farragut North. That lead to major backups up to Shady Grove on the west side of the line and Glenmont on the east side. At the height of the problems, riders were forced to wait up to 45 minutes.

By the time trains arrived from outer stops on the line, they were often packed with riders. Some trains, nearly full, bypassed stations where the platforms were too crowded.

Javier Homet, who boarded at Friendship Heights, said he saw the warnings at the station about delays but didn’t think it would be that bad. About 8:45 a.m., he started to worry that he would miss his 10 a.m. flight from Reagan National Airport to Phoenix.

“I would have taken a taxi,” Homet said as he stood shoulder to shoulder with other passengers.

Near him, Christopher Amherst, who had boarded a train at Shady Grove and was trying to reach Dupont Circle, said, “I’m looking forward to the [Capital] Bikeshare coming to Bethesda.

“Then I don’t have to deal with the delays of the Red Line,” he said.

“I’d rather pay Bikeshare than Metro.” At least, he said, “I can get to work on time.”

Metro sent its first alert to passengers about the problem near Judiciary Square at about 4:50 a.m., Stessel said.

Another alert at about 6 a.m. said crews were working to replace the rail and estimated that it would take two hours to fix.

Trains returned to normal service about 30 minutes later than expected, at 8:35 a.m., because large equipment had to be moved off.

Stessel said it is not yet known what caused the problem with the switch point. The incident is under investigation.

“It was certainly a very difficult morning for the Red Line,” Stessel said. “We certainly apologize to customers for the inconvenience. We know it was a rough morning.”