The MTA is speeding up its plan to install an advanced safety technology on its commuter rail lines. But there's no magic bullet when it comes to preventing train crashes.

The technology -- called positive train control -- is untested and unproven on commuter lines as large and complex as Metro-North and Long Island Railroad. And George Bibel, author of Train Wreck, reminds riders that it's not foolproof: in 2009, a version of the system was in use on the Washington DC Metro when two trains collided, killing nine people.

Still, safety inspectors say positive train control would probably have prevented the Spuyten-Duyvil crash. But there are still questions, such as, how much automation is too much? And, can taking control from human operators paradoxically reduce safety?

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