Regarding the safety system son trains mentioned by some of you:
A friend of mine studied aeronautical engineering and ended up in constructing trains (they 'use' aerodynamics as well). He told me that the locomotive drivers developed the strangest ideas in order to circumvent the system.
When it used to be a pedal, they put a brick on it.
When it was a button, the made the button stick with paper or some scotch tape.... One even devised a spring loaded system to push and release the pedal, because the system would also shout the alarm when the pedal remains pushed all the time.
Generally speaking, I see no problem to sleep if certain technical and human precautions are in force - JUST DO NOT TELL THE PAX. No matter how safe it is, it would be picked up by some newspaper sooner than later.
Regards, Bernhard