Before–after study of pavement roughness impact on vehicle fuel consumption and emissions

• Pavement rehabilitation reduced fuel consumption and CO 2 emissions by about 10%. • Connected vehicle data enabled high-resolution before–after analysis. • Greater savings observed on segments with positive longitudinal grades. • Daily savings exceed 540 L of fuel and 1.42 tonnes of CO 2 emissions. This study evaluates the impact of pavement rehabilitation on vehicle fuel consumption and CO 2 emissions along the M−50 motorway in Madrid (Spain) using a before-and-after approach based on connected vehicle data. The methodology integrates fleet composition analysis, filtering for free-flow conditions, segmentation into homogeneous sections, and the definition of a representative “design vehicle” to isolate the effect of improved surface condition. Complementary statistical tests and disaggregated analyses by vehicle type and road grade confirm that an average 27% reduction in pavement roughness led to approximately 10% decreases in both fuel consumption and CO 2 emissions per vehicle, with greater savings on uphill segments. When extrapolated to actual traffic volumes, the rehabilitated sections are estimated to save over 5.5 million litres of fuel and 15,000 tonnes of CO 2 annually in one travel direction. These findings highlight pavement maintenance as an effective strategy for improving transport energy efficiency and contributing to road transport decarbonisation goals.