US study finds obeying speed limits could save up to 70 L of fuel per vehicle each year

Researchers examined more than 120 million trips made by light‑weight gasoline vehicles on U.S. roads. They found that 43.2 % of journeys included at least one speeding episode, with drivers exceeding limits for about 11.7 % of travel time.

Simulating a scenario in which no driver exceeded the posted limits predicts a 2.4‑3 % reduction in fuel consumption. This translates to roughly 70 liters of fuel saved per vehicle per year, or about 25 million liters per day across the U.S. light‑vehicle fleet—equivalent to over 9 billion liters annually. The reduced fuel burn would cut CO₂ emissions by around 57 000 tonnes each day, or more than 20 million tonnes per year, and generate monetary savings estimated at $22 million (≈€19 million) per day.

The authors note that the time penalty for obeying speed limits is minimal—adding less than a minute to the average daily travel time—suggesting that slower driving is a straightforward, low‑cost measure to improve fuel efficiency and reduce greenhouse‑gas emissions.