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Positive Train Control


Positive Train Control

A Metrolink train approaches Pomona Station.

Christopher MacKechnie

Positive Train Control

What is Positive Train Control?

Positive train control is an active safety system that helps avoid train collisions. Data that shows information about the upcoming trip (speed limits, the presence of other trains, construction zones) is uploaded to the engineer's cab before the train departs. When the train is en route, GPS systems track the train's speed and location and compare it with the previously uploaded information. When it is time for the engineer to adjust the train's speed, a display in the cab informs him or her - and if they do not respond, the system can take over and engage in actions up to and including bringing the train to a stop.

By automating the train in a certain fashion, positive train control in effect brings commuter and freight trains closer to rapid transit systems such as BART in San Francisco and the Washington Metro. In the latter two systems, all train movement is - or can be - controlled by the transit system's headquarters. Of course, the magnitude of difficulty is much greater on a line that is not totally in segregated right-of-ways, as BART and Washington Metro are, but automated control is still easier along a track than it would be for a car, and we all know how far Google has come with its experimentations in driverless cars.

Why do we need Positive Train Control?

The recent push for widespread adoption of positive train control has come in response to the horrific Metrolink train crash in Los Angeles in September 2008 that killed eighteen and wounded many more . In that crash the engineer of the Metrolink train was texting and therefore missed a red signal, causing the train to crash head-on into an oncoming freight train. Positive train control would have averted the crash by automatically stopping the train after the engineer failed to do so.

Federal Action on Positive Train Control and Industry Pushback

After the Metrolink train crash, one of the improvements in passenger rail safety that came about was the Railroad Safety Enhancement Act, which mandated that all track in the United States be equipped with positive train control by 2015. Unfortunately, as I write this in February of 2012 industry lobbyists are fighting to get this 2015 deadline pushed back to 2020 or even beyond. The Association of American Railroads and the American Public Transportation Association argue that the $13 billion required to install this system nationwide is too high - especially for transit systems that have seen their funding drastically dissipate in recent years - given the rarity of train accidents. Accidents are rare - since 2001 only 21 accidents could have been avoided by this system; these accidents killed 53 people, injured 1,000 others, and caused $60 million in property damage. In other words, if we assume a 30-year lifespan for this technology than the cost works out to be about $81 million per death saved, a number that is very high from an economic perspective. From a business perspective, it would be cheaper to pay out damages when an infrequent death occurred, especially given that a 1997 federal law limited total railroad liability in any one accident to $200 million.

Los Angeles Metrolink is Pushing Ahead

While most of the industry is attempting to delay the implementation of positive train control, one agency - the Los Angeles Metrolink commuter railroad - is pushing ahead. Metrolink plans to have all of its network completely outfitted with positive train control by 2013, thereby becoming an industry leader in the process. Metrolink knows that for a commuter transit line the perception of safety is critical to the success of the line . The installation of the train control is proceeding concurrently with the construction of additional grade separations with an eventual goal of eliminating all grade separations along the track.

Other Benefits of Positive Train Control

In addition to safety benefits, positive train control can help to reduce travel time by allowing trains to operate closer together like subways and other rapid transit lines can. However, by itself this benefit cannot justify the technology.


Although the cost is high, passenger railroads have no alternative but to implement this system if it can save any lives at all. The rarity of train accidents causes each one, in a way similar to the rarity of airplane accidents, to be blown up in such as way that it makes train or plane travel seem more dangerous than automobile travel, even though deaths in auto accidents are orders of magnitude greater than deaths in auto or plane accidents. If we ever hope to see increased usage of public transit in this country then we cannot afford another disaster like the Metrolink crash of September 2008.

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