Last time I went on a road trip with 4 friends from uni we found that these songs get the best reactions from people sitting in the cars next to you in traffic jams when you open all the windows, turn them to full volume and sing and dance like tits:

Wham! - Club Tropicana
Aneka - Japanese Boy
Culture Club - Kharma Chameleon
N.W.A - smurf the Police
Carl Douglas - Kung Fu Fighting
Boston - More than a Feeling

I highly recommend all of them. Especially Club Tropicana, highlight of the journey being stuck next to some random guy in his Mercedes with his little sunglasses and smart shirt and tie on who started dancing like a total spastic along with us.