If you have a habit of pressing the gas pedal a little harder to shave time off your commute or run errands faster, new research suggests you may want to reconsider. Not only does speeding burn more fuel and pump more harmful gases into the atmosphere — it barely saves you any time at all.
The findings come at a particularly relevant moment, as gas prices have remained high through the summer and drivers are feeling the pinch at the pump during everyday travel and road trips.
A study published Thursday in the Nature journal Communications Sustainability found that if American drivers simply followed posted speed limits, the country could collectively save an average of $22 million per day in fuel costs — based on prices at the time of the study — along with 6.7 million gallons of fuel and 57,000 metric tonnes of carbon dioxide emissions daily. Researchers say that reduction in emissions would be roughly equivalent to removing about 5.5 million passenger cars from the road.
Researchers at the University of Minnesota examined data from 120 million vehicle trips taken across the country on four Wednesdays in 2021. They used information from national road networks, posted speed limits, and elevation data from the U.S. Geological Survey. The analysis focused on roads with speed limits of 45 mph (72 kph) or higher.
What they found was striking: more than 43% of the trips studied included at least one instance where the driver exceeded the speed limit, and drivers spent nearly 12% of their total time behind the wheel going faster than allowed.
Despite the common belief that speeding gets you there faster, the time savings turned out to be minimal. With an average daily driving distance of 28.6 miles (46.03 kilometers), sticking to the speed limit would only add about 54 seconds to a driver’s day.
“If your goal is to shave one minute off your time, then you’ve got to drive fast. If your objective is to get to your destination safely and to save fuel, then you might drive slower than the speed limit,” said William Northrop, a mechanical engineering professor at the University of Minnesota and co-author of the study.
The research also looked at battery-electric vehicles, though that portion of the analysis was limited to California given the level of EV adoption in the U.S. at the time. Northrop noted, “We find that driving slower is beneficial for EVs as well.”
The study also revealed differences between states. Nevada stood out for both how often drivers sped and by how much. Florida, Georgia, and North Carolina had high rates of speeding, though drivers there did not necessarily exceed the limit by as large a margin. Meanwhile, Montana, Wyoming, Idaho, and South Dakota showed the lowest rates of speeding overall.
The connection between speed and fuel consumption comes down to basic physics — the faster a vehicle travels, the more energy it requires and the more emissions it produces. While vehicle engines have grown more efficient over the decades even as cars have gotten larger and more powerful, speed limits have also risen since the 1970s, when the Emergency Highway Energy Conservation Act set a national 55 mph cap during the energy crisis of that era.
When factoring in today’s average gas prices and increased miles driven, researchers estimate Americans could save closer to $26 million and 7.2 million gallons of fuel per day this year simply by easing off the accelerator.
The study does acknowledge one limitation: driving more slowly across the board could affect traffic flow in ways that might influence overall efficiency.
The research is especially timely given that gas prices have climbed above $4 per gallon this year following disruptions tied to the war in Iran. Fuel efficiency experts have long pointed to speed reduction as one of the easiest ways to stretch a tank of gas further. If enough drivers cut back on fuel use, it could even influence broader demand in the oil market, potentially affecting prices.
Rob Middleton, an associate research scientist in mechanical engineering at the University of Michigan who was not part of the study, praised the work but offered some perspective on its scale. The fuel savings identified, while significant, still represent only a small portion of the roughly 375 million gallons of gasoline consumed in the U.S. each day.
“It’s a big number, but it’s a small fraction,” Middleton said. “This is a ‘freebie’ in that it doesn’t really cost anyone anything to do.”
He also emphasized the ongoing importance of fuel efficiency improvements as electric vehicles continue to make up only a small share of vehicles on the road. “The market penetration of selling EVs is still small, so we still need fuel, we still need ICE (internal combustion engine) vehicles, we’re still going to have them for a very long time,” he said. “Things that we can do to either make the new ones better or to improve our fuel supply, we need to do.”
