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Both trains in the Metro crash were being operated on automatic mode, which meant the computerized system was supposed to determine if conditions on the track were safe for travel. Metro trains are operated on automatic mode during rush hour.

The Washington Metro has used the automated system since its inception in 1976. Similar automated systems have existed in rapid-rail systems in various cities across the United States and abroad for more than 30 years. The idea of an automated train control system hasn't changed much, but the hardware and technology in the control rooms have been improved.

"It fundamentally works," said Louis Sanders, chief engineer at the transportation association. "It's a very efficient system. Just because it was designed 30 years ago doesn't mean it's not a good system."

There is no federal agency that mandates technology standards for rapid transit systems. The standards are regulated by local jurisdictions.

In an automated system, a control room houses electronics that regulate the movement of trains. The control rooms send electronic signals to sensor-like devices located between the train tracks.

When a train crosses over one of these devices, the device relays critical information to the train's lead car, telling the train when to slow down, speed up and stop. When trains are running on automatic mode, the operator's main task is to open and close the train doors.

"The design of the system is set up to keep trains separated, to have positive separation between trains, to control speeds, to give them speed information. And so what we're trying to figure out is what happened in this accident," National Transportation Safety Board member Debbie Hersman told CNN's "American Morning" on Wednesday.

The automated system includes safeguards for the train operator, including an emergency, or mushroom-shaped, brake which can be applied when the train is running both in manual and automatic mode. NTSB officials say the train operator appeared to hit the "mushroom" brake before the crash.

On Wednesday, however, NTSB investigators discovered "anomalies" in an essential control circuit on a section of track where the accident occurred.

Hersman said the circuits are "vital providing information to the operators and the train itself when on automatic." NTSB officials wouldn't elaborate on the "anomalies."

A full NTSB report of the investigation won't be released until six to 18 months from now, but officials said they will simulate crash tests to determine what caused the accident. Until the report is released, transit authorities say they won't be likely to know what improvements or changes need to be made in other urban rail systems.