A new study from the Insurance Institute for Highway Safety (IIHS) found that combining automatic braking with rearview cameras and sensors can cut reverse crashes by 78 percent. Rear automatic braking alone, which is an option in just 5 percent of new vehicles, is linked to a 62 percent drop in reported backup accidents in cars with that equipment. CBS News reports: Starting in May, all new cars in the U.S. will be required to have a rearview camera. Some automakers are going further by adding backup warning sensors and reverse automatic braking. For the first time, the Insurance Institute for Highway Safety tested that combination of technology. Two models -- the 2017 Subaru Outback and Cadillac XT5 SUV -- earned superior ratings. Four other vehicles scored an advanced rating for generally avoiding a collision or substantially reducing the vehicle's speed. But there's some room to improve. One vehicle did not stop automatically when backing up to a dummy car parked at an angle. Automatic braking in the front will become standard in most cars in 2022 but there's currently no plan to make it standard for backing up.