Overview
- The peer‑reviewed study was published July 16 in Communications Sustainability after researchers modeled more than 120 million real vehicle trips recorded over four days in 2021.
- Using those trip reconstructions, the authors estimate that if light‑duty gasoline cars obeyed posted limits on roads of 45 mph or higher, the U.S. could save about $22 million a day in fuel in 2021 prices and 6.7 million gallons of gasoline while cutting roughly 57,000 metric tonnes of CO2 daily.
- When adjusted for higher 2026 pump prices, reporting noted aggregate savings rising to roughly $26 million and about 7.2 million gallons of fuel per day.
- The study finds speeding is common—over 43% of trips had at least one speeding event and drivers spent nearly 12% of driving time above the limit—and shows clear state differences such as high excess speeds in Nevada and high prevalence in Florida, Georgia and North Carolina.
- Authors caution the analysis omits how slower driving might change traffic flow and the effects of aggressive acceleration, so they are launching instrumented electric‑vehicle tests and micro‑scale driving studies to refine estimates and gauge real‑world policy impact.