An automated safety system would have been active in the rail terminal where one Norristown High Speed Line train struck another last week, but its effectiveness may have been limited by the conditions at the end of a line, SEPTA officials said Tuesday.

For the first time since the crash, SEPTA managers detailed the Automatic Train Control system that works to maintain safe conditions on the 13.4-mile route. They would not discuss specifics of the crash, citing an ongoing National Transportation Safety Board investigation. But they did speak in general terms about how the system worked.

A single-car train carrying 42 people ran into an empty parked train about 12:15 a.m. Aug. 22 at the 69th Street Transportation Center, the last stop on the line. Thirty-two on board, including the train's operator, suffered injuries. The crash raised questions about the line's safety from lawyers representing one of the people hurt, and U.S. Rep. Robert Brady (D., Pa.) even proposed a temporary end to service on the route, which connects 22 stops from Norristown to Upper Darby.

The passenger who is suing SEPTA has contended the train appeared to be speeding as it approached the terminal.

The NTSB has not ruled out anything as a possible cause, a spokesman said Tuesday. The federal agency has said, though, that it would notify any transportation agency if its investigation revealed a systemic safety problem. SEPTA officials said they had not received any information since the crash that would prompt them to shut down or curtail service on the line.

SEPTA conducted an inspection last week on the brake systems of all cars used on the line and found no defects, general manager Jeff Knueppel said.

The Norristown High Speed Line has ATC active on every portion of the track traveled by passengers, said Mike Montasero, SEPTA's chief engineering officer for communications and signals. That includes the terminal at 69th Street. ATC, he said, has five principal functions: preventing speeding, maintaining a safe space between trains, ensuring stops at signals, alerting a train to broken rails, and ensuring the safety of workers on the rails.

Along with providing a safety net for train operators, ATC's protections allow rail agencies to run a busier railroad, said Narayana Sundaram, director of engineering and commuter rail for the American Public Transportation Association, an advocacy group promoting public transit.

"It allows you to be much more efficient, and actually have shorter headways and run more trains in the same amount of time," Sundaram said.

There are elements of the system that work differently in a terminal like 69th Street, though, officials said.

"Terminals are complicated," Knueppel said. "ATC is meant to slow things down as you get to the terminal. Then, as you get to a terminal, there are specific operating rules."

The speed limit approaching a bumper, or the end of a line, on the Norristown High Speed Line is 15 mph, he said. Within the terminal, an operator will typically call in for permission to enter, but the way trains move through the terminal can vary, with operators and yard personnel potentially having greater influence.

While ATC should alert an operator to the presence of another train on the tracks, that control operates differently within a terminal, where trains are moving at slow speeds, there is a higher density of vehicles on the tracks, and tracks are configured with crossovers and stopping areas.

SEPTA officials said they would not be more specific about the way ATC works in a terminal, out of concern about speaking on matters that may be under NTSB investigation. If the NTSB, or SEPTA's own review, revealed a systemic mechanical problem, officials would move quickly to address it, Knueppel said.

"It's not our style to wait," he said. "We see something that's an issue, we'll be moving on it."

SEPTA has spent about $750 million on its signaling system, which includes automatic safety protections, since the early 1990s, he said. That work means all but two spans of track in SEPTA's network — the Media/Sharon Hill Line and the Broad-Ridge Spur — have signal systems that have been installed within the last 30 years. Those two areas are undergoing signal improvements.

The Norristown High Speed Line was the first route in SEPTA's network to be installed with ATC after multiple accidents, including one at 69th Street in 1986 that was similar to last week's crash. SEPTA installed ATC on the route from 1991 to 1996 for $30 million. Before it was installed, the signal system worked like traffic lights on a road, with the operator solely responsible for ensuring a train was traveling at a safe speed and stopping properly.

More recently, SEPTA has spent more than $300 million to install Positive Train Control, a more advanced protection, on Regional Rail. That work is largely complete, Knueppel said, with work focusing now on ensuring SEPTA's system can interact with Amtrak-controlled lines and freight trains that use SEPTA tracks.