A new study by Dr Omid Ghaffarpasand and Professor Francis Pope from the WM-Net Zero project analysed over 50,000 real-world vehicle emission measurements from Birmingham to understand whether a car’s market price can predict how much pollution it produces. Using remote-sensing data and a machine-learning model trained on more than 108,000 UK used-car listings, the authors estimate each vehicle’s retail price and compare it to its emissions.
The results reveal a clear and consistent pattern: cheaper cars emit more air pollution. This applies even when comparing cars within the same Euro class. The study finds a strong inverse relationship between vehicle price and emissions of NO₂, NO, CO, and PM. For diesel cars, the correlation is extremely strong (R² up to 0.97), and the effect is much larger than for petrol. Each £1,000 increase in diesel vehicle price is associated with a 0.44 g NO₂/kg-fuel reduction, while petrol shows only 0.02 g improvement.
A key insight for equity and public health is that the lowest-priced cars (£1,000–£5,000) emit roughly twice as much as cars in the £15,000–£20,000 range. This means lower-income households—who tend to own these cheaper vehicles—may involuntarily contribute more to local air pollution, reversing the usual pattern seen in greenhouse gas emissions. As the authors note, this reveals “a previously overlooked transport-related emission inequality,” where affordability aligns with disproportionate pollution.
The findings highlight important implications for clean-air zones, scrappage schemes, and net-zero transport policy, suggesting that price-based indicators could help better target high-emitting vehicles.
Read the full paper here:
https://www.sciencedirect.com/science/article/pii/S0959652625024333