I work my police scanner to get situational awareness. Thinking about what's going on up ahead keeps my mind busy. If there's little traffic I'll scan for airplane transmissions or search for frequencies of the towns going by (if I'm in unfamiliar territory)

I'm far too nervous about what the other drivers are going to do next to get drowsy. Maybe you should be more fearful?

In truck driving school they advised a 30 minute nap. Less isn't as effective and more will put you into a groggy state when you try to get going again.