This document summarizes a study that analyzed vehicle safety data to determine if vehicle size or weight has a greater influence on safety. The study found that reducing an SUV's weight by 20% through the use of aluminum slightly improved safety, but increasing the vehicle's size by only 4.5 inches through the use of aluminum improved safety even more, reducing injuries by 26%. Therefore, the study concludes that size, not weight, is a better determinant of vehicle safety when it comes to protecting all passengers in a crash. Aluminum allows automakers to increase vehicle size without significantly increasing weight.