or more and that force becomes much greater. gravity is low enough and it's heavy enough up here, it will stay on the tracks. that's not the case back there. the center of gravity is different back here. the weight distribution is different and that's why some passenger say they felt the car sort of flying up off the tracks. we know that can happen because we saw it happen in spain when this train crash occurred. the train was supposed to be going 50 miles per hour. instead, it was going over a hundred. watch you who it slings those passenger cars off behind it and they pull the locomotive off behind them. this is why investigators knew to look at excessive speed because it is something that they have seen before. >> with speed clearly being a major factor in this, a lot of people will be looking to the train engineer for answers. steven ditmeier is an adjust professor. >> he was involved in the creation of amtrak. he joins us now from alexandria,