News release

From: Springer Nature

Environment: Avoiding speeding could have saved US drivers $22 million daily in 2021

Approximately 25.4 million litres of fuel (6.7 million US gallons), 22 million US dollars, and 57,000 tonnes of carbon dioxide emissions could have been saved across the USA every day in 2021 if all light duty vehicles had driven at or below speed limits. The findings, published in Communications Sustainability, also suggest that this would have resulted in an average of only around 54 additional seconds of travel time per person per day.

Breaking the speed limit directly increases both a vehicle’s energy use and the emissions from internal combustion engine vehicles. Abrupt acceleration and deceleration when speed limits change also reduces efficiency. Although these relationships are well known, there has been limited quantitative analysis of the costs of speeding at a country-wide scale.

Bharat Jayaprakash and William Northrop analysed more than 120 million journeys taken on US roads by light duty vehicles (those weighing up to 3,860 kg, or 8,500 pounds). The data were recorded on four days across 2021 — one day per season. Overall, 43.2% of trips included at least one instance of speeding, and during these trips, vehicles spent around 11.7% of their journey time travelling above the speed limit. When the same trips were modelled without speeding, the authors report daily savings of around 25.4 million litres of fuel. This would have saved consumers approximately 22 million US dollars per day, based on the fuel prices on the specific days analysed, and would also have reduced daily carbon dioxide emissions by approximately 57,000 tonnes. Extrapolating these figures to a year, avoiding speeding would have saved the equivalent annual fuel consumption of approximately 5.5 million US cars, and more than 6.7 billion US dollars at 2021 average fuel prices ($3.10 per US gallon).

The research does not account for how such widespread changes in driving behaviour would affect traffic patterns, so further work is needed to understand the full real-world effects. However, as the analysis only included roads with a speed limit of 45 miles per hour (approximately 70 kilometres per hour), both the overall prevalence of speeding and the potential savings may be underestimated.