When I'm on a weekend road trip, I don't have any time for sleep. I want to get to my destination as soon as possible, enjoy my stay there for as long as I can, and then rush back just in time to go to my next class. Unfortunately, I don't function very well with no sleep, so I compromise by keeping the time occupied with sleeping and the activities accompanying it (ie, getting a hotel room), to a minimum. This is one of the reasons why I frequently sleep in my car during short Road Trips. (See Rituals for more) Consequently it usually takes me a week or two to recover my sleep pattern from a good Road Trip.
While on a recent road trip to Las Vegas, I was returning home along I-40 through Texas and Oklahoma, to I-35 north into Kansas. I had a good friend in Kansas, and my intention was to crash at her house for a few hours. It was about 4:00am, I had been driving for about 17 hours already, and I started to get rather tired, so I made the mistake of taking a Vivarin caffeine pill. I started to wake up a bit. I measured the time it took for the thing to hit me, and about how long it lasted. I started to get tired again after a while, and took another, planning to keep up a rhythm of caffeine to avoid tiredness. This turned out to be a bad call, as I started shaking and feeling really weird, almost hallucinating. By the time I got to my friend's house I had been driving for about 22 hours continuously, and I was starting to go into shock, or at least very messed up in the head. It would have been a better idea to pull off the road at a rest stop and sleep for a couple of hours, but I was too headstrong for that. Anyway, taking more than one or two Vivarin is a pretty bad idea. I used to drink Crappuccino (see Rituals) to stay awake while driving at night, and that worked pretty well. I've found that the sugar in soft drinks makes me really tired, so I always stay away from Coke at night when I'm driving.
A good way of staying awake without using chemicals is to crank up the music, roll down the window, and sing really loudly. Probably the best way to stay awake, however, is to have a good Co-Pilot to talk to, whose job is to keep you (the driver) awake. I'm never tired whenever I'm participating in an interesting conversation with someone, no matter what time it is or how long I've been driving.
Anyway, it's a good idea to constantly examine your own state of alertness when you're driving late at night, and find out what works best for you. And remember, it's always better to pull off the road and sleep at a rest stop for a few hours than to fall asleep while driving and trash your car.