Increasing the fuel economy of motor vehicles means that they will be made lighter. Does that imply that there would be an increase in traffic deaths? As presented in a new study our answer is "no": if the weight reductions are made with safety in mind, they would substantially improve safety. The greatest challenge is probably to resolve the incompatibility of light trucks with cars, including making light trucks (and heavier cars) lighter - without reducing their safety dimensions. In addition, the lightest cars should be made larger in selected ways - which can be done without making them heavier. These changes would result not only in increased safety but also increased fuel economy.