Granite Geek: The Tech That Makes Trains Stop

May 19, 2015

Last week’s deadly Amtrak derailment outside of Philadelphia has prompted serious scientific inquiry into the nature, effectiveness, and cost of the safety mechanisms in use in some of these trains.

For more on a braking system that could have slowed the train down is David Brooks. He writes about science in his weekly Granite Geek column for the Nashua Telegraph and Granitegeek.org. He spoke with NHPR's Peter Biello.

What is this breaking system called and how does it work?

Positive Train Control (PTC) is the name that’s used in the system as a general name for it and it uses data gathered locally in the train itself and data from satellites to make decisions about what to do. So basically what it does is it has a satellite system that’s keeping track of the train and taking a look at what the speed is and comparing it to a database about what part of the track it’s on and what should be happening on that part of the track, and if those two figures are off, or if it’s going much faster than its supposed to, in theory it can autonomously apply brakes on the train, regardless of what the engineer does.

Amtrak’s “Downeaster” line which runs from Boston up to the Seacoast area in NH into Maine does not have this system. Why not?

It’s not slated to even get the system down the road because it doesn’t have enough traffic. Basically the system is very expensive, it’s difficult, the equipment is moderately expensive, but the hard part is setting up the databases, integrating the databases so that all the train companies using the line can have it, and in buying the spectrum so that the signals can be maintained, which is one of those things that’s actually quite difficult. There’s not a lot of it out there and everybody wants to make use of it for something that’s making money, like broadcasting television or wireless internet, and so getting spectrum is difficult and Amtrak has said that’s one of the issues on why it wasn’t turned on yet in Philadelphia at the time of the accident.  So anyway, all of that’s expensive so they only do it in places where they think the return is really worth it and they’re just aren’t enough trains running every day between northern Boston to justify it.

So the reason that trains like the one in Philadelphia that do need it but don’t yet have it or don’t have it fully activated is largely a question of money.

That’s what it seems to be and logistics. With any large computerized data system, any company, any government agency, any organization will know it’s difficult turning on systems that involve lots of other different systems working together, which is what this is, so I’m sure there were logistical issues as well, but as far as I can tell it’s mostly money.

And coincidentally David, Science Café New Hampshire, which you moderate, is scheduled to talk in Nashua this week about the technology of trains. This was planned before the disaster outside of Philadelphia. How is the talk going to change given the recent events?

As always, the Science Café is driven by questions from the audience. As everybody knows, we’ve been doing this for four years now. It’s not really a lecture. It's basically a couple of experts that get together in a bar and people show up and ask them questions about the topic at hand. So I’m certain that many of the questions will be about brakes and braking systems and automated systems and safety whereas it might not have been before. For example I did an interview and one of the panelists, and he is an engineer expert on train systems down in Massachusetts for 15 years and so I did an interview with him last week in preparation for a column I wrote. I didn’t talk about brakes at all and then, of course, the accident happened, so I called him back and talked to him again and he’s quite knowledgeable about it. So whatever people want to talk about, we’ll talk about, but I suspect that many questions will be about that.

The Science Café is convening Wednesday, May 20 from 6-8 p.m. at Killarney’s in Nashua.