That was one of the games we played on the long drives we made every summer from DC to Maine and back again: Zip Zap Zam Zooey.
Zip = VW bug = 25 pts. Zip Zap = red VW bug = 50 pts. Zip Zap Zam = VW van = 75 pts. Zip Zap Zam Zooey = red VW van = 100 pts.
We also played "Find the letters of the alphabet in order one by one on signs you pass". And then I personally played a game called, "Try Not to Get Carsick", which I invariably lost, often more than once.