down. if he runs past a red signal, the it will automatically stop him. it s based on technology that s been around for decades. now, that would only occur if this were a situation, again, like the may 2015 philadelphia amtrak crash where the train operator was going around a curve much too fast or the one back in 2013. it would slow it down. but if there was a rail break, like the rail broke under the train or an axle broke, positive train control isn t going to do anything. i also want to bring in on the phone former ntsb investigator in charge and a railroad accident investigation expert. we were reporting just a little bit earlier, russell, that the ntsb has of course launched their go team. explain to us exactly what that is and what they ll be doing. a go team is a set number of specialists in different aspects