Speeding incurs substantial environmental and economic costs nationwide for negligible travel time savings

Abstract Speeding is a known contributor to high energy use and emissions in road transport, yet its large-scale impacts remain underexplored. Here, we analyze over 120 million vehicle trajectories from four representative days in 2021 to quantify energy consumption, costs, and emissions from speeding for light-duty internal combustion engine vehicles across the continental United States and Hawaii and for battery electric vehicles in California. Two speed limit interventions on highways and arterial roads are evaluated and extrapolated to the national vehicle fleet. We estimate that adherence to posted speed limits could save more than 6 million gallons of fuel, 18 million US dollars, and 50,000 metric tonnes of carbon dioxide per day, while increasing travel time by only 54 seconds per driving day. On an annual basis, these savings are comparable to removing about 5.5 million conventional passenger vehicles from the road.