An empty Metro train drove through a red light, mangled a switching apparatus, and entered the tracks used by oncoming trains near the McPherson Square station on July 15, Metro officials confirmed yesterday.

They blamed the incident on human error and a breakdown in an automatic safety system.The driver was suspended and the defective fail-safe system is being investigated.

The incident occurred two weeks ago on a stretch of track linking the Red and Blue lines of the subway shortly after passenger service had ended for the day, according to Ralph Wood, director of rail service.

The train was crossing a short segment of track linking the subway's Red Line with the month-old Blue Line, on its way to the National Airport station.

The train passed through the red light at 5 to 10 miles an hour and over a partially closed switching apparatus leading to the Blue Line. The fail-safe system designed to stop trains from entering the Blue Line when the switch is not fully open failed to check the train, Wood said.

The train performs the same exercises throughout the day, and is often making the cross from Red Line to Blue Line at peak traffic hours, bringing additional cars into service, Wood said.

Another fail-safe device prevents trains operating manually from exceeding 15 miles per hour, he added.

The driver, who was suspended for five days, told Metro authorities that she did not see the signal, Wood said.

"She shouldn't have been able to get across from th Red into the Blue Line. If nothing else she should have been derailed," he said.

"I'm having an investigation into why the yound lady didn't stop before she got to the Blue Line," he said.

General superintendent of Rails Anthony Stefanac said that passing through the "red light was an absolute infraction of the rule. You can be damn sure no one else is going to run through any red signals."

"I honestly can't say that," he added a moment later.

Stefanac said there could not have been a collision under any circumstances because the Blue Line's fail-safe system would have stopped all oncoming trains from hitting any train that might be in its path.

He acknowledged that the errant train, which was operated manually, would not have been subject to any safeguards but would be dependent upon its operators' visual sighting of oncoming trains.