mr. goglia said to make sure that they'll look at the mechanics. was there some mechanical malfunction in the braking system, for example that might have contributed to the accident or some other failure. >> now, the ntsb investigator also talked about a so-called deadman's switch which can stop a train if an engineer loses consciousness, for example. listen. >> oftentimes in place of the deadman switch they have an alerter. so if there is no taitt from the engineer within a certain period of time the aural and visual alerter will activate in the cab of the locomotive. >> what role could that play in alerting an engineer to a problem? >> well i think the idea is to essentially create a noise, or if he might have dozed off, to essentially wake him up and realize he's got the take control of the train. this train did not -- does not have the override capacity so that as some trains do. so if speeding excessively, to be able to slow it down. so i'm not that familiar with all of the mechanics of this. but an alerter system as i understand it essentiall