What metaphors are used in The Hitchhiker's Guide to the Galaxy by Douglas Adams?

"When you're cruising down the road in the fast lane and you lazily sail past a few hard-driving cars and are feeling pretty pleased with yourself and then accidentally change from fourth to first instead of third thus making your engine leap out of your hood in a rather ugly mess, it tends to throw you off your stride in much the same way that this remark threw Ford Prefect off his"

This is an apt metaphor to suggest how Ford thought he was in control of the situation and assumed nothing could surprise him—after all, he knew Zaphod—but then abruptly realizes things are going very astray. He is not, in fact, in control at all.