Read "The Hitchhiker's Guide to the Galaxy" by Douglas Adams online for free on Textopian. Full text with search, annotations, highlights, and AI-powered reading aids.
The aircar rocketed them at speeds in excess of R17 through the steel tunnels that led out on to the appalling surface of the planet which was now in the grip of yet another drear morning twilight. Ghastly gray light congealed on the land.
R is a velocity measure, defined as a reasonable speed of travel that is consistent with health, mental well-being and not being more than, say, five minutes late. It is therefore clearly an almost infinitely variable figure according to circumstances, since the first two factors vary not only with speed taken as an absolute, but also with awareness of the third factor. Unless handled with tranquillity this equation can result in considerable stress, ulcers and even death.