Play stupid games with whoever your in the car with like A-Z bands, footballers, movie stars etc.
Take some playing cards. You can play that, but obviously not with the driver!
Take some crosswords or suduko.
Actually, if I were you I wouldn't go to sleep the night before and stay up watching telly or something, and then sleep on the journey haha.
Just talk to who your in the car with. You've got 16 hours, you can go through your life stories lol.
Oooh, sweet and sour, that's a good game. You wave to people in cars and if they wave back they are sweet, if they look at you like you're a psycho they are sour. Sounds childish, but it's amazing what bordem can do to you.
Erm...are you a girl? If you are you could paint your nails.
Yeahhhh, you're gonna be really bored lol. Just think of things to talk about with whoever your in the car with. I find some right stuff out about my Mum on long-distance journeys!