Metro Crash in DC claims seven lives and could take more. It could have been a lot worse. The way the crash took place between Takoma Park and Fort Totten stations on the Red Line on the inbound, that is coming into Washington DC, side of the track means that the train was not nearly as crowded as it could have been if the accident had happened on the outbound half, which during evening rush tends to be the far more crowded trains.
While we don't know for sure what happened just yet, my bet is that there is going to be a combination of signaling error and operator error. Metro simply can't afford to have the "automatic" safety program to be declared a problem because it is the heart of the Metro system's operation.
That being said, even operator error is going to be hard to take and not just because it is hard to speak ill of the dead. The stretch of track invovled here has a curve which can been seen from the photos of the scene and if a train is coming in at normal operating speed, the curve would hide the stationary train until it was too late to prevent a crash.
Of course, this is all speculation.
My heart goes out to the families of those who are gone and those who are injured.
If you look at this photo, you can imagine how much momentum has to have been carried by the striking train. That front car had the bottom ripped out and the top of the car shoved some nearly 50 feet over the back of the last car of the stopped train. The train cars are about 60 feet long or so and there are three doors on each train with the middle door being about 30 from either end. The ladder in teh background is set at the middle set of doors, 30 feet or so from either end of teh train. That is a lot of force to be carried through.
From here you can get a sense of the curve.
Finally, you can see the upper shell of the striking train's first car.