In 1974 the speed limit on highways in the United States was reduced to 55 miles per hour in order to save fuel  In the first 12 months after the change, the rate of highway fatalities dropped 15 percent, the sharpest one-year drop in history  Over the next 10 years, the fatality rate declined by another 25 percent
It follows that the 1974 reduction in the speed limit saved many lives
The fatality rate in highway accidents involving motorists driving faster than 55 miles per hour is much higher than in highway accidents that do not involve motorists driving at such speeds.