No it's not. Positive train control is universal on high speed lines. As soon as the train approaches a red or yellow without slowing the brakes will go into fu

No it's not. Positive train control is universal on high speed lines. As soon as the train approaches a red or yellow without slowing the brakes will go into full emergency. Most such systems will also enforce a full stop if the speed limit (which the train knows, and is based on the derailment speed with a healthy margin). The only real credible threat is mass violence against the passengers. That could just as easily occur in any crowed public space.