During a pilot study conducted by the Federal Highway Research Institute (BASt) in collaboration with the company HEAT and DTV Traffic Consulting Ltd., the feasibility of remote sensing for measuring vehicle emissions on German highways was investigated. The study employed the EDAR (Emission Detection and Reporting) system, which captures license plates and real‑time exhaust data as vehicles pass a fixed sensor array. Over twelve measurement days at a single site on a federal highway, the system recorded more than 120,000 individual vehicle passes. Of these, 84 % were classified as valid, and 82 % of the valid records corresponded to vehicles registered in Germany. The remaining third of valid data came from foreign‑registered vehicles, for which only limited technical information was available.

The average speed of vehicles at the measurement point was 100 km h⁻¹, with a slight positive or negative acceleration due to the site’s slope. The system proved capable of capturing up to 10,000 vehicles per day, demonstrating high productivity for statistical analysis. The data were linked to vehicle technical characteristics supplied by the German Federal Motor Transport Authority (KBA) database, allowing classification by emission standard, engine type, and vehicle class. Among passenger cars (class M1), the fleet was roughly evenly split between gasoline and diesel engines, with an average age of eight years. Gasoline cars had a mean power of 94 kW and a curb weight of 1,800 kg, while diesel cars averaged 113 kW and 2,400 kg. Hybrid vehicles represented 4.3 % of the passenger fleet, and 68 battery‑electric cars were also detected.

For heavy goods vehicles (class N3), the study provided the first real‑time emissions data on German autobahns. NOx and particulate matter (PM) concentrations measured by the EDAR system were consistently higher than the values predicted by the HBEFA 4.2 model for highway traffic. The discrepancy suggests that current emission factors may underestimate real‑world emissions, especially for older or non‑Euro‑VI compliant trucks. The data also revealed that foreign‑registered vehicles exhibited higher NOx and PM levels on average, underscoring the need to identify major emitters for targeted regulation.

The project’s objectives extended beyond data collection. A comprehensive data‑protection concept was developed in cooperation with BASt to address the capture of license plates, ensuring compliance with privacy regulations. The study also evaluated the operational limits of the EDAR system, confirming its suitability for deployment on multi‑lane highways with a required slope and overhead mounting capability. The findings demonstrate that remote sensing can reliably capture large volumes of emission data in real traffic, providing a robust basis for ambient pollution assessments and informing future emission control policies.

The collaboration involved HEAT, DTV Traffic Consulting Ltd., and Dr. Jens Borken‑Kleefeld, with BASt providing funding and regulatory oversight. The pilot study, conducted over a 12‑day period, established the feasibility of remote sensing for highway emissions monitoring and highlighted areas for further research, such as refining emission factor models and expanding coverage to additional sites.