Individual driving style has a big influence on the climate impact of automobiles, one that is sometimes even a greater than the type of car being driven, according to a new analysis. The methodology suggests a route for drivers to reduce their environmental impact without having to buy a new car.

Transportation accounts for one-quarter of European greenhouse gas emissions, and passenger cars and buses are responsible for nearly half of that. But the transition to electric cars has been unfolding more slowly than expected, and some people cannot afford to buy new, more environmentally friendly automobiles.

Internal combustion engine cars will likely remain on the road for many years to come, so new strategies to make transportation more energy efficient and cut emissions that take this reality into account are needed, researchers from Politecnico di Milano in Italy argue in the journal Scientific Reports.

The researchers used data from existing emissions studies to develop a new methodology for estimating fuel consumption, carbon dioxide, and nitrogen oxide pollution from individual cars. Crucially, they linked these impacts to driver behavior such as how fast a person drives, how hard they brake, and how hard they accelerate. These simple measurements have a surprisingly robust correlation with actual tailpipe emissions—which would be impractical to measure directly at scale.

Then, the researchers collaborated with an Italian insurance company to access a database of information from “black boxes” containing a GPS unit and an accelerometer installed on over 8,000 private cars in Italy. They analyzed data on over 11 million trips totaling more than 190 million kilometers to assess the environmental impact of individual cars.

For example, fuel consumption and carbon emissions are minimized in a “green speed” range between 50 and 75 kilometers per hour.

“Our new methodology shows how to use known and well established models and combine them with the driving data and vehicles characteristics to generate a customized measure of environmental impact of any car,” the researchers write.

Current environmental standards for passenger cars in Europe are based on car technology and age. But the new methodology that takes driver behavior into account provides a more accurate measure of the actual environmental impact of driving than the current Euro Class rating system, the researchers found.

The cars in the insurance company database included 59 Euro Class 3, 1,283 Euro Class 4, 1,563 Euro Class 5, and 5,552 Euro Class 6 vehicles. “While it’s commonly assumed that higher Euro standards correlate with lower emissions, our analysis uncovers a more complex reality,” the researchers write.

They used their methodology to group the vehicles into 4 clusters based on environmental impact, finding 636 vehicles in the worst performing group, 1,688 in the next, 2,001 in the next, and finally 4,132 vehicles in the best performing group.

Some of the Euro Class 6 vehicles had worse actual environmental performance than some of the Euro Class 4 vehicles in the study. In other words, driving eco-friendly vehicles long distances in an aggressive, inefficient manner leads to greater greenhouse gas emissions than driving older vehicles in a virtuous, environmentally responsible way.

Policymakers could use this new methodology to, for example, manage access to car-restricted areas of city centers and set parking fees based on the actual environmental impact of vehicles.

The approach places greater responsibility on drivers, but also offers a fairer, more inclusive approach to sustainable mobility, the researchers argue, enabling incentives for virtuous driving without requiring people to purchase specific types of cars.

Source: Strada S.C. et al. “An innovative virtual sensing system for the vehicle-centric evaluation of emissions in the sustainable mobility transition.” Scientific Reports 2024.

Image: via Unsplash.