Yeah - funny thing, when I find I'm dead tired (the 2 times this happened), I've found even 15 minutes with the eyes closed helps. It's usually on a LONG drive home, into the sun - I'm not sure if the 15 minutes is rest, the sun moving, or what. Thankfully, I tend to know where the legal rest areas are, and I'm not so stupid as to insist on driving if I'm tired - I will pull over to rest