Near-Road Measurements of Turbulence Generated by Passing Vehicles

Motor vehicle emissions, such as nitrogen oxides and particulate matter, pose a major environmental and public health concern. These pollutants are strongly influenced by traffic-induced turbulence—eddies generated by moving vehicles—which controls how emissions disperse near roads. To better understand this turbulence, we conducted a field experiment along the shoulder of a major highway using three high-frequency (20 Hz) ultrasonic anemometers in a triangular setup. All sensors were mounted 1.5 meters above ground; two were adjacent to the roadway, and the third was 9 meters away. Over a three-hour period on a hot spring afternoon, we recorded 3D wind velocities and temperature fluctuations. We analyzed mean flow, Reynolds stresses, turbulent kinetic energy, and mixing scales. Temporal segmentation captured the unsteady nature of vehicle-induced disturbances relative to background turbulence. Spectral analysis revealed wake signatures and interactions with ambient flow. These findings provide new insights into the structure and anisotropy of traffic-generated turbulence and its role in near-surface pollutant dispersion.