No MARTA trains have collided in 30-year history

MARTA trains have been running for 30 years, and in that time no MARTA train has ever collided with another, officials said Monday.

Rich Krisak, assistant general manager of rail operations, would not speculate on what caused the fatal Metro train collision in Washington, D.C. But he said the rail transit systems in Washington, Atlanta, San Francisco and Miami “probably have the most sophisticated control systems in the U.S.”

MARTA uses an automatic train control system that’s designed to be fail-safe.

“As long as you’re running with that protection, it’s virtually impossible for you to hit another train,” Krisak said. “It’s actually regulating the speed of the train and won’t allow you to enter another train’s territory.”

The system separates trains by a safe braking distance.

“It depends on the speed,” Krisak said. “If you’re going 65 to 70 (miles per hour), it gives you a lot more braking distance. It assumes a worst-case rail adhesion, that the wheels are worn, the track is worn and it’s raining outside.

“It’s very conservative.”

The system has two elements: on-board technology and a network of trackside installations filled with communication and signaling equipment. Constant feedback flows back and forth.

The system also constantly checks trains for equipment malfunctions.

“If it senses one, it will stop the train,” Krisak said.

Contrary to what some may think, there is no huge central computer controlling everything.

“The fail-safe nature is in the wayside components,” Krisak said. “We could totally lose the control center and the system could run just as safely.”

Krisak noted, however, that with human intervention or human error, no system is 100 percent foolproof.