I find that the old "would you rather?" game helps liven up long motorway journeys. Here we go … "Would you rather that the car ahead of you was driven by Paul, who's just knocked back the hair of the dog at the motorway services pub before merging back into your lane from the slip road?" or, "would you rather be behind Rob, who is alert, has his eyes on the road, but shared a cannabis joint earlier in the day?"
The answer I'd expect is, "I'd rather drive behind Rob. He's probably as clear-headed as I am if a few hours have passed since the joint. Half-drunk Paul might be dangerous though. And what's a motorway services pub ? No one would allow that".