Around-the-clock operational requirements of transport and communication systems may exceed the human capacity to work efficiently and safely. Nowadays, it is possible to be reached at all times, which brings the private and professional spheres closer together. Increased intensity in role overload of the professional and private life can entail psychological stress and sleep complaints. The consequence is fatigue, sleepiness, enhanced sensitivity to stressful or negative emotional stimuli and impaired alertness and performance due to being awake at times that are biologically programmed for sleep, prolonged wakefulness and restricted sleep over time. Sleep is all too frequently sacrificed in favor of other demands, desires, or dictates. The consequences of impaired alertness may be devastating in all kinds of drivers, truck drivers, pilots, train drivers where fluctuations in performance may present significant occupational safety hazards. It has been estimated that between 15 and 20 % of all motor vehicle accidents are attributable to fatigue and daytime sleepiness. Sleep disorders as obstructive sleep apnea, as well as restricted sleep may compromise an individual’s capability to maintain alertness over longer periods of time. In conclusion, experts agree that there is no substitute for sleep: “Sleep debt can only be paid back with sleep.”