A black Volkswagen Golf rolls along at 12 mph on an empty road in the heart of Virginia’s horse country. Suddenly the dashboard lights up, and there’s a warning sound. The driver ignores it. A moment later, the VW brakes hard—all on its own—and comes to a stop a foot in front of an inflated box painted to look like the rear end of a car. The Insurance Institute for Highway Safety (IIHS) has been running tests like this a few times a month at its research center in Ruckersville, Va.