it a positive train control system. that type of system it is designed to enforce the civil speed to keep the train below its maximum speed. and so we have called for positive train control for many, many years. congress has mandated that it be installed by the end of this year. so we are very keen on positive train control. based on what we know right now we feel that had such a system been installed in this section of track, this accident would not have occurred. >> had the system been installed, this crash would not have occurred? this is not a history and this is not hard. this is not rocket science. this is not curing cancer. we also know that we need to do it.