One freight train sped through a stop signal before crashing head-on into another in the Texas Panhandle last month, killing three crew members, according to a preliminary report on the accident from the National Transportation Safety Board.
NPR's David Schaper reports the fiery wreck appears to be the type of collision that the NTSB and other safety advocates say might have been prevented by an automatic braking system called Positive Train Control.
The NTSB says that the stretch of track where the crash occurred does not currently have Positive Train Control installed but is due to have it by the end of the year.
The board has been calling on railroads to implement the safety technology for decades. In 2008, after a train crash killed 25 people, Congress required passenger and freight railroads to install the system, but the process has been delayed. An original 2015 deadline has been extended, at the railroad industry's request, to 2018.
As we've previously reported, Positive Train Control — also known as PTC — slows or stops a train if an operator is going too fast or misses a signal.
"Positive train control uses GPS track sensors and other sensors to determine both the speed the train is traveling and if there are any obstacles up ahead," the Two-Way wrote in 2015. "It knows the speed limit on every stretch of rail, so if a train is going too fast for whatever reason, it slows it down."
The implementation of the safety technology has been delayed for several reasons. One is the price.
As NPR's Jeff Brady reported last fall, the mandate to install the technology "is most expensive for freight railroads, which have tens of thousands of miles of track to include in their PTC systems."
But there's also a problem with radio interference, as David wrote last year:
"It's a problem that's bedeviled PTC from the start, says Karl Witbeck, an engineer who has worked on the system.
" 'Part of the challenge is that, in urban areas in particular, a lot of people are trying to access the spectrum,' he says. 'It's important to cellphone coverage, police and fire communications; stores even use it to track merchandise as it's scanned.'
"To use a subway-train metaphor, it's like each car is a band in the spectrum and you can put only so many people in each car before it is full. Once it is full, you can't put any more people, or communications, on that band.
"And no matter how badly you need to get on that train, Witbeck says, you can't just shove your way onboard. ...
"The obvious solution is getting railroads their own piece of the spectrum, Witbeck says, and the expectation was that the Federal Communications Commission would allocate sufficient spectrum for the nation's railroads to use. But that didn't happen, and instead the railroads had to buy it on their own."
And on top of that, there were delays in approving the thousands of trackside radio antenna towers required for PTC, David reports.
The result: Months after Congress' original deadline for all American freight and passenger railroads to have PTC installed, many sections of track still lack the technology.
That's why when the operator of a train near Panhandle, Texas, sped past a stop signal, there was nothing in place to stop a fatal crash. The NTSB says that train was going faster than 60 miles per hour as it headed toward the head-on collision.
The Amtrak derailment in Philadelphia last year, which killed eight and injured more than 200, could also have been prevented by the technology.