Critical systems meant to deter a Metrorail disaster failed in the moments before and after one six-car Red Line train rear-ended another at high speed near the Fort Totten station, records and interviews show.

Reams of documents released Tuesday by the National Transportation Safety Board, collected during an eight-month investigation into the June 22 Red Line crash that killed nine, bear out Metro's struggle to maintain its infrastructure, from complex electronic signaling equipment to simple radios.

A maintenance crew noted five days ahead of the crash that a critical track circuit was malfunctioning, but the transit system allowed trains to continue running. The circuit was "bobbing" -- one moment it might pick up a train's position, the next it might not.

A work order then was created 6:50 a.m. June 17 for "intermittent" failure in a high-frequency track circuit.

A similar work order for the same circuit was opened Feb. 28, 2008, and closed Sept. 26, 2008, but the NTSB found no information on the remedial action taken.

Metro mechanics performing scheduled testing June 18 recognized the same problem. They made no adjustments because "the weather was turning bad" and they issued no report "because the problem cleared itself while they were troubleshooting," according to the NTSB.

The track circuit sends its signals to transmitter and receiver modules in the Fort Totten control room. Those "were of early 1970s vintage," the NTSB reported, and were scheduled to be replaced the week of the crash.

Outside of the track circuits:

»  Train 112, consisting of six 1000 Series cars, the oldest and most damage-prone in Metro's fleet, was not equipped with on-board data recorders, challenging investigators to determine its speed. Within eight seconds of the crash, according to circuit data, the head of Train 112 was traveling between 48.3 and 56.3 mph.

»  Radio communication was patchy as staff in Metro's operations command center struggled to hear the "black/black" call of a collision from the operator of the train that was struck, Train 214. Bernard Floyd, a command center controller, told investigators that the problem is "not unusual."

»  On April 24, a Metro "track walker inspection report" noted a blind spot in a section of curved track near what would later be the crash site. It is not clear whether Metro installed an advanced warning device there, as the system aims to do.

»  A review of a telephone system that allows personnel in one train control room to communicate with personnel elsewhere found inoperative jacks, disconnected wiring, and broken terminals.