Bar Code Racing 2

(Inspired by [popbottle]s Bar Code Racing - this is what I expected when I read the title.)

A toy car (with motorised drive and steering) has a bar-code reader mounted underneath. The toy-car-track has bar-code-like markings along the whole track.
The bar-codes contain data of the track ahead, much like a rally-car navigator's notes; degrees of incline, degrees of corner, length of straight, etc.
The toy cars drive themselves, using the available data to control speed and steering. But drive too fast, and you might not get a good "read", or your systems might not be able to respond fast enough to slow down for the next turn.