Due to the nature of rail transportation, it's pretty unusual to hear of a three-train crash, but one happened today about 11 miles north of Valparaiso, Indiana. One train crashed into the rear of another, apparently causing cars to jackknife and push a passing train off the neighboring rails. They all seem to be CSX trains.
Two crew members were injured (presumably the ones operating the train that hit the rear of the other one), but none of the others were hurt. Residents have been evacuated from the area, however. At least one of the trains had some tank cars, some chemicals appear to have spilled, and a fire was triggered by the crash.
I am baffled why rear-end crashes like this still happen with trains, though. I don't know enough about how electronic signaling systems work, but coming from my computer and networking background, it seems like detecting the presence of two trains on a single segment of track really shouldn't be hard. Seems to me that each locomotive should broadcast its presence along the rails and listen for any others. Simply finding if two trains occupy the same segment of track isn't sufficient to prevent a collision, but would usually slow trains down before a collision occurred (repeaters connecting adjoining track segments would be needed to create a zero-collision system).
Well, I'll save further pontification for later. For the moment, here are a few links related to the crash: