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Science & Technology

Speed Control Technology Could Have Stopped Amtrak Derailment


Since the derailment, there's been a lot of talk about something called positive train control. It's a technology designed to automatically slow or stop trains before a derailment or a collision. In 2008, Congress mandated that positive train control be installed throughout the rail system by the end of 2015. It was not installed at the Amtrak crash site. Yesterday, the NTSB said had such a system been installed along that stretch of rail, the accident wouldn't have happened. For more on this, we're joined by Steven Ditmeyer. He's former director of research and development at the Federal Railroad Administration. Welcome to the program.

STEVEN DITMEYER: Thank you, Melissa.

BLOCK: And, first of all, do you agree with the NTSB that if there were positive train control along this stretch of track that this crash wouldn't have happened?

DITMEYER: Yes. If this train had been moving along - and because the engineer was not slowing down - the PTC system would have brought the train down to the proper speed to go through that curve.

BLOCK: How does the system work?

DITMEYER: PTC systems use positioning technology, digital data communications, onboard computers and computers at the control center. In the case of Amtrak's PTC system, they have installed transponders - radio frequency ID devices - between the rails at very specifically measured locations. And those transponders contain information about speed limitations ahead. And when a train passes over it, its radio receiver detects that and so the onboard computer knows that there is a speed restriction ahead. And if the engineer doesn't obey it, the system intervenes.

BLOCK: And is it only for excessive speed? In other words, if there were something on the tracks, would positive train control detect that and slow a train down?

DITMEYER: No. Positive train control doesn't have vision ahead to see if there's something blocking the tracks. However, if there is another train there, the nature of the Amtrak PTC system knows the location of trains ahead and stops the following train from colliding with it.

BLOCK: How complicated is it for railroads to put this positive train control system in place?

DITMEYER: PTC is a relatively complicated system. Amtrak's version of PTC was developed around the year 2000 so that they could install it and get permission to run their new Acela train sets at higher speeds than the traditional Northeast Corridor trains. They installed it between New Haven and Boston because Acelas would be traveling at 150 miles an hour over portions of that territory. And they installed it on other parts of the corridor where the Acelas would be running at higher speeds. There have been some problems encountered in the intervening years. For one was getting sufficient radio frequencies assigned to the railroads to handle these new systems. The radio frequency issues seem to have been overcome, and Amtrak has all along been talking of having PTC over the entire route implemented by the end of this calendar year, which is when the federal mandate required it.

BLOCK: And does that seem doable?

DITMEYER: Yes, it does.

BLOCK: Is it an expensive system to put into place?

DITMEYER: Yes, it is. It's hundreds of millions of dollars for Amtrak and for the commuter railroads that operate on Amtrak in the Northeast Corridor. The freight railroads are implementing a slightly different version of PTC that uses GPS positioning, and they have been spending something on the order of $5 billion for the freight railroads in the U.S.

BLOCK: You know, with any deadly accident like this, whether it's a plane crash or, in this case, the train crash, there's always a really brutal cost-benefit analysis that goes into safety measures and whether the cost is worth it given how rare accidents might be. Is there that sort of calculus going on with positive train control?

DITMEYER: Well, that calculus has been taking place over the years leading up to this incident. And there has been a general conclusion on the part of railroads, unions, the federal regulators and so on, that the safety benefits alone do not justify the very large investment in PTC. However, there are potential other benefits that derive from PTC, including the ultimate potential of improving train running times, reliability, asset utilization and track capacity. But the safety benefits alone - unfortunately, there appears to be agreement that they alone do not justify the capital expenditure.

BLOCK: Steven Ditmeyer, thanks for talking to us.

DITMEYER: Melissa, thank you.

BLOCK: Steven Ditmeyer is adjunct professor of railway management at Michigan State University. He's also former director of research and development at the Federal Railroad Administration. Transcript provided by NPR, Copyright NPR.