Monday, December 09, 2013
Positive Train Control and Commuter Lines: A Train Wreck of Another Kind
Early Sunday morning, Dec. 1, dozens of people living in Westchester County and points north of New York City along the Hudson were riding in a southbound Metro North commuter train driven by veteran engineer William Rockefeller Jr. The scenic rail line follows the east bank of the Hudson and makes a sharp curve just north of the Spuyten Duyvil station. According to information leaked by a union official later, Rockefeller "basically nodded" at the controls in his booth at the front of the train, which was electrically linked to the locomotive that was pushing the train from behind. Whatever Rockefeller's state of mind was, the speed recorder recovered from the train verified that it hit the curve at 82 MPH (131 km/hr), well above the 70-MPH (112 km/hr) speed limit for the straight stretch of line north of the curve, and way too fast for the 30-MPH (48 km/hr) zone in the curve. The result? The locomotive and all seven cars derailed, four persons were killed, and over 60 were injured. As bad as this literal train wreck was, it highlights a different kind of train wreck that is taking place at commuter lines across the U. S.: one involving a federally-mandated system called Positive Train Control (PTC).
There is little doubt that if the Metro North train operated by Mr. Rockefeller had been equipped with PTC, the accident would never have happened. As passed into law by Congress in 2010 and required in all trains by the end of 2015, PTS is a system that takes information on a train's location and automatically enforces speed limits in accordance with track regulations, operating conditions, and other factors. (Think of it like a car equipped with a cruise control that would automatically slow you down to 20 MPH (32 km/hr) in a school zone even if you stomped on the gas.) So even if Mr. Rockefeller had fallen asleep with his foot on the "dead-man" control (which automatically stops the train if a driver lets go of it), the train would have slowed down safely before it reached the 30-MPH zone.
So why didn't Metro North install PTC already? Many freight lines have completed their installations, and even the Brotherhood of Locomotive Engineers and Trainmen, a union which does not happen to count Mr. Rockefeller as one of its members, has issued a call for PTS to be installed as soon as possible in all commuter trains.
There are a couple of reasons, which can be summarized as suitability and cost. PTC was developed and intended mainly for long-distance freight lines to prevent derailments and other accidents involving hazardous cargo. Freight-train engineers are often on 24-hour call, and so sleep-deprivation-induced inattention is a real danger, which is one reason freight lines have adopted it so fast.
Commuter lines, with their regular schedules, frequent starts and stops, and much more dense traffic and line networks, are a different sort of problem. While PTC often relies on GPS for some of its functions, GPS doesn't work underground, which is where many commuter lines spend a good bit of time. It turns out that the unfunded mandate to install PTC on all U. S. commuter lines might cost as much as $2 billion, which is a lot of change for cash-strapped municipalities. Even before the crash, many commuter lines had given notice that they were going to miss the deadline, and there was talk of legislating an extension for such lines. But clearly, PTC was too late to help the four victims of Sunday's crash.
Not all engineering ethics issues are clear-cut, and rail safety is one of them. One of the first ethical cases to draw the attention of the IEEE, the largest professional organization of electrical engineers in the world, involved a commuter rail line. In 1972, as BART, the Bay Area Rapid Transit System of San Francisco, tested its new state-of-the-art automatically controlled train cars, a non-injury accident occurred which led whistleblowers to go public with their doubts about the design. There are similar concerns that PTC technology is not ready for commuter lines, and if fully installed would either slow down the trains so much that schedules would have to be changed, or might take automatic actions that could cause accidents instead of preventing them.
Metro North trains already have several safety systems installed such as the "dead-man" switch, but reportedly a second type of "alerter" system, which required the engineer to respond to a beep by tapping a control every 25 seconds, was available only in the locomotive itself at the rear of the train, not in the front cab where Rockefeller was. Investigations of many kinds of accidents often reveal that safety equipment was installed that could have prevented the mishap, but it was either not operating at the time, was disabled, or not available under the particular circumstances that prevailed.
As the controls and software capable of replacing some, if not all, of the functions of a human driver become more available, either economic forces or the force of law will push both private and public entities to adopt them. We are seeing this already with Google's self-driving cars, and while PTC does something close to the same thing, it has been out of the public eye until now. But the same type of tradeoff exists for both PTC and self-driving cars. The promise of much lower accident rates is offset by the expense and administrative headaches of implementing the systems.
The immediate cause of Sunday's accident is pretty clear by now. Mr. Rockefeller did the honest thing by admitting he was sleepy. When even locomotive-engineer unions call for the installation of potentially job-threatening systems such as PTC, it's a sign that the technology's time has come. As long as it can be adapted safely and economically to the demands of commuter lines, we can look forward to the chance that the four people who died on Dec. 1, 2013 might be the last lives lost in a U. S. train accident for many years.
Sources: I referred to reports on the accident carried in the New York Daily News on Dec. 5 at http://www.nydailynews.com/new-york/bronx/metro-north-engineer-sleep-disorder-article-1.1538717, a statement issued on Dec. 5 by the Brotherhood of Locomotive Engineers and Trainmen at http://www.blet.org/pr/news/newsflash.asp?id=5507, a CNN report on the crash published on Dec. 4 at http://www.cnn.com/2013/12/04/us/new-york-train-crash/, and the Wikipedia article on Positive Train Control.