An especially ridiculous feature on older vehicles, vacuum-operated windshield wipers were a perfect example of a mechanical compromise that utterly failed under pressure. These wipers relied on the engine's vacuum pressure, meaning their speed was directly tied to the throttle. When a driver accelerated—the exact moment they needed clear visibility on a highway—the wipers would slow down, sometimes to a near-halt. When the driver let off the gas, the wipers would suddenly speed up. This unpredictable, frustrating operation made them inherently unsafe and led to their well-deserved replacement by reliable, electric motors.
