"Studies on railwaymen......any bearing on flight crew..?" Apples and oranges, save that, if the suggestion is that such levels of rest are "safe", it's worth observing that even the comparatively low-level mental task of recognising and acting on a red danger signal is not achieved. As recently as the 90's there was still a shockingly high incidence of SPAD (signals passed at danger) events. Back in the days of steam these mostly weren't even recorded unless they resulted in an accident.
Last edited by ShotOne; 11th August 2016 at 18:29.