I'm surprised that there haven't been more scenes like this. This accident seems extreme, but riding the Green line is always a dangerous, herky-herky, scary, amusement park ride. The T could really use some "automation."

It may be an issue with the emergency break. I believe those cars, like most modern trolleys, have an electromagnetic emergency break. When triggered it basically drops down from the bottom of the car onto the tracks and turns on, bringing the car to an instant halt. If that's the issue, its not likely something the driver would trigger - i.e. the car's computer triggers these things when the car stops operating in normal parameters (too fast, too much wheel slippage etc.) or when the computer thinks those conditions exist. If the car was moving at a decent clip and literally came to a complete halt instantly, I'd bet on the break.

The Tab follows up, finds out why the train suddenly stopped: Apparently, a woman told the driver she needed to get off right now, so the driver applied the emergency brake. The T told the reporter that's not appropriate; worker now faces disciplinary action.