I know a narcoleptic who is able to drive in town, but absolutely cannot drive on the autobahn-style US interstate highways between cities for very long, at any time of day.<p>It has to do with orexin.  Orexin helps keep you awake.  But you produce less of it when you are sedentary or bored.  When there is mental engagement with a task, it is easier to stay awake.<p>The very qualities that make limited access highways useful for most of us, to get places more quickly, make them deadly for people with orexin-deficiency sleep disorders.<p>That&#x27;s why I hope polyphasic sleep experimenters only drive on the <i>interesting</i> or <i>challenging</i> stretches of road.