system. if joe boardman and amtrak tell mess they'll beat the deadline of december then i'm confident that they will. >> let me ask you, because when you say positive train control, i spent half my morning reading about this. for people watching they may have no idea what that is. so let me have you just explain that what that is and why in such a busy area, you know this northeastern corridor, why it was absent on this particular curve. >> well positive train control in its simplest form overrides human error. it is built in along the trackside and on each locomotive so it can begin to slow and stop the train when human error occurs for whatever reasons. positive train control would obviously have prevented this accident but even positive train control is not infallible. but it would have probably prevented this accident. again, you start with that