Why is it a bad idea to drive a vehicle with anti-lock brakes (ABS) as if it does not have ABS?

ABS provides anti-skid protection only when the driver applies the brakes hard enough that the wheels would otherwise lock up. During firm braking, the ABS system rapidly releases and reapplies brake pressure dozens of times per second to keep the wheels rolling at the threshold of grip, preserving steering and reducing skids. If you brake lightly (or release the brakes when you feel them pulse), the ABS system never activates and you lose its benefit. The correct technique with ABS is to brake firmly and steadily during emergencies and steer where you need to go — the ABS will keep the wheels from locking up automatically. Pumping the brakes (the old technique for non-ABS vehicles) defeats the ABS system.