Metro's alert system continues to fail periodically in the area of track where one Metro train crashed into another last month, killing nine and injuring more than 70 people.

A component of the automatic train alerting system that may have failed to prevent one train from knowing another was stopped ahead on the track continues to flicker intermittently in that same spot even when new equipment is used, National Transportation Safety Board member Debbie Hersman testified Tuesday. The device removed just five days before the crash as part of routine maintenance doesn't fix the problem, either.

The revelations were part of a three-and-half hour congressional oversight hearing in which officials testified about the deadly June 22 crash and the transit system's overall funding shortages and lack of regulation.

The continuing problem at the crash site is why Red Line riders are still experiencing delays along the line more than three weeks after the crash.

"It's serious enough for me that we are running an 'absolute block' there. Operators have to go at a slower speed," Metro General Manager John Catoe later told reporters.

That means trains are only allowed one at a time through the stretch of track near the Takoma station to avoid any crashes in the area. Therefore, the transit system cannot run as many trains on the line, leading to backups, crowded cars and delays that have left riders grumbling.

Jackie Jeter, president of the union representing Metro train operators, testified that some train operators have told her since the crash that they have had similar signal problems in the past.

Catoe said he has seen no records showing any prior problems like that. He said he was "unable to give any legitimacy" to her comments.

Metro tested all 3,000 circuits in the system after the crash, Catoe said, and repaired three circuits that did not perform at the level Metro would like. However, Catoe said they did not have the same flickering problems as the one near the crash site. Two of those circuits were in rail yards, while one was along the Blue Line.

But neither Metro officials nor the NTSB investigators currently know how to fix the problem of the flickering device.

That is why the NTSB gave Metro an urgent recommendation Monday to continuously monitor the train alert system instead of checking it daily as they have done since the crash. Previously, they had checked it monthly.

Metro officials have said such a monitoring system does not exist and they will have to build one. Catoe said he plans to meet with a vendor Wednesday morning to discuss creating such a system for the agency.

He also said meeting the NTSB's safety recommendations would be his first priority if Metro receives more federal stimulus money or $150 million that a congressional subcommittee appropriated late Monday.