going 106 miles an hour in a 50 mile-per-hour area? >> certainly the things that we usually look at and just big categories generally speaking the human, the machine and the environment. were when i talk about environment, we're talking things like visibility and rain and sleet and snow and obviously we didn't have rain sleet or snow the other night but want to make sure visibility or whatever was not a factor. mechanical issues. look at mechanical conditioning of the train. the braking system. the mechanics of the track, signal system and finally when it comes to the human, we're talking about the human performance. fatigue an issue? distractions an issue? was the engineer on a cell phone? those are generally the three disciplines we're going to look at in trying to put together a puzzle such as this. >> mayor nutter announced not long ago that as far as philadelphia knows, the city of philadelphia knows, everyone has now been accounted for.