Illustration of Positive Train Control system
Media playback is unsupported on your device
Video

Amtrak crash: How Positive Train Control system works

Following the fatal crash of an Amtrak train in Philadelphia, the spotlight is on the Positive Train Control (PTC) system.

This system prompts automated safety triggers when a train is nearing risky areas.

While parts of the US railway system have PTC installed, the area where the recent accident occurred did not.

The BBC explores how PTC is designed to operate.

  • 15 May 2015
Go to next video: Derailed train 'was speeding'