Site of train disaster didn’t have speed control system

Aired: 5/13/2015 | 0:05:30 | Clip
Investigators says that the Amtrak train that derailed in Philadelphia was going more than twice the speed limit for that part of the rail before the engineer tried braking. Hari Sreenivasan talks to Robert Sumwalt of the National Transportation Safety Board about the monitoring system that helps stop trains traveling above the speed limit and what investigators are looking for.