Safety investigators don't know why the train was speeding, but the circumstances suggest precisely the sort of event the automatic system — known as "positive train control" (PTL) Digital communications combined with GPS can monitor train locations and speeds, talk to trains and automatically take charge when a train needs to be slowed.
In December 2013, a Metro-North commuter train derailed on a section of track in the Bronx, killing four, after the engineer headed into a 30-mph curve at 82 miles per hour. That track also lacked the automatic control system.
Congress mandated that all railroads install an automated braking system that could have prevented the crash. The deadline is 2015, but many railroads — wary of the cost — have failed to comply and are pushing for delay.
