Why We Sleep

Figure 12: Sleep Loss and Car Crashes
Drunk driving and drowsy driving are deadly propositions in their own right,
but what happens when someone combines them? It is a relevant question, since
most individuals are driving drunk in the early-morning hours rather than in the
middle of the day, meaning that most drunk drivers are also sleep-deprived.
We  can  now  monitor  driver  error  in  a  realistic  but  safe  way  using  driving
simulators.  With  such  a  virtual  machine,  a  group  of  researchers  examined  the
number of complete off-road deviations in participants placed under four different
experimental conditions: (1) eight hours of sleep, (2) four hours of sleep, (3) eight
hours of sleep plus alcohol to the point of being legally drunk, and (4) four hours of
sleep plus alcohol to the point of being legally drunk.
Those in the eight-hour sleep group had few, if any, off-road errors. Those in the
four-hour  sleep  condition  (the  second  group)  had  six  times  more  off-road
deviations  than  the  sober,  well-rested  individuals.  The  same  degree  of  driving
impairment  was  true  of  the  third  group,  who  had  eight  hours  of  sleep  but  were
legally drunk. Driving drunk or driving drowsy were both dangerous, and equally
dangerous.
A  reasonable  expectation  was  that  performance  in  the  fourth  group  of