Poured in a low arc across parking lots, school approaches, and access roads that municipalities have decided are moving too fast for their own good, the speed bump is topography with a moral. It rises perhaps four inches, sometimes painted in fading yellow chevrons, sometimes left the color of everything else, a gray suggestion easy to miss until it announces itself through the suspension.
Its behavior is entirely reactive. It does nothing to a car that approaches slowly, offers only a gentle bureaucratic nod. To a car moving too quickly, it delivers a small, specific violence, a jolt to the undercarriage that seems designed less to prevent speeding than to punish it retroactively, once the crime has already been committed. Cyclists regard it with more caution than drivers, having learned that four inches is a different number depending on which vehicle you're in. Over years, it is worn smooth by traffic, its paint erased first at the crown, where tires visit most, so that by middle age it has a faint white stripe like a part in gray hair. Skateboarders use it as a modest jump; delivery drivers memorize its exact location the way sailors memorize a reef. It asks for twelve miles an hour and receives, on average, something closer to nine, out of spite.