Rhyming Chain
Cat, hat, mat, flat. Keep going until you run out.
Find A, then B, then C, on every sign you pass.
The classic car game. Needs nothing, works from the age of four, and lasts a surprisingly long stretch of motorway.
Rien du tout.
Scanning the environment for a specific letter is exactly the visual discrimination that early reading depends on, and children will do it for far longer in a car than at a table. The strict ordering also adds a working memory load.
The driver does not play.
None.
Cat, hat, mat, flat. Keep going until you run out.
One of you thinks of something. The other has twenty yes-or-no questions.
A list of things to spot, and quiet for twenty minutes.
Ten words, one code, and a conversation nobody else can follow.
You give three random words. They build a story around them.
Close your eyes. What made that noise?