Evaluation of a cost-effective roadside sensor platform for identifying high emitters

High-emission vehicles (high emitters) likely have significantly higher nitrogen oxide and particle number (PN) emission factors compared to other vehicles. Effective identification of these vehicles in road traffic requires efficient and cost-effective instruments. In this study, a compact, cost-effective sensor platform was developed and evaluated in a field experiment. The platform was deployed on a roadside, and we measured pollutant concentrations in the exhaust plumes of four diesel trucks with various aftertreatment systems, cargo loads, and driving speeds. The sensor platform successfully measured carbon dioxide, PN, and nitric oxide (NO) concentrations, and the data were used to derive the plume-based emission factors of these pollutants. By considering both NO and PN emission factors, three diesel trucks with failed or outdated aftertreatment systems were successfully identified as potential high emitters. The NO emission factor obtained by the sensor platform was consistent with that of the benchmark portable emission measurement system. The sensor platform also effectively elucidated the differential influences of aftertreatment systems and driving conditions on emission factors. This pilot test demonstrates the feasibility of a sensor-based system for high emitter identification. Owing to its cost-effective and compact design, the proposed sensor platform has greater potential for mass networked deployment than regular-size instruments, thereby effectively supporting regulatory protocols for screening high emitters on public roads.