Drivers could save 2.4 billion gallons a year by obeying speed limits, study finds

A study by the University of Minnesota Twin Cities says drivers could collectively save about 2.4 billion gallons of fuel each year by simply obeying posted speed limits. Researchers assessed speeding’s effects on fuel use, pollution, and costs using real driving data from more than 120 million trips on four different days in 2021, one per season. They compared recorded behavior with scenarios where vehicles never exceeded limits, linking routes to U.S. Geological Survey data on road type, speed limits, and elevation. On a single day, staying within limits reduced fuel by 6.7 million gallons and lowered carbon dioxide by about 62,800 U.S. tons (57,000 metric tons), worth nearly $22 million. The report also found that driving 10 mph above the limit can raise fuel and carbon pollution by up to 21%. Time impacts were small—about 54 seconds longer per day, or roughly 6.3 minutes per week—yet speeding was linked to 11,775 road deaths in the U.S. in 2023.