Study on local air pollution caused by NOx from diesel freight vehicle

An on-board measurement system that simultaneously measures road traffic, vehicle running conditions and exhaust emissions was installed in a diesel freight vehicle with two tons payload. Actual NOx mass emissions were compared with that measured in a typical test mode for urban cities on a chassis dynamometer. The frequency of vehicle accelerations in actual urban cities was found to exceed that of a typical test mode for urban cities on a chassis dynamometer, which resulted in increased NOx from actual running conditions compared with the typical test mode for urban cities. The dynamics of NOx emissions at an actual roadside was also analyzed. It was observed that NOx emission based on distance with an actual city route test was about two times higher than that of a free way route and a typical test mode for urban cities. The reason for high NOx with the city route was explained by the higher frequency of lower gears at which higher NOx is emitted. In the city route NOx emission to roadside was serious during vehicle accelerations at an intersection. It was emerged that intensive NOx roadside pollution was occurred in case of vehicle acceleration at an intersection. The reason was that vehicle was accelerated in lower speed at higher engine load. This seems to be one of the reasons for serious NOx roadside pollution. The results from this study will be useful for a construction of road infrastructure and a traffic management with less NOx pollution as well as establishing an exhaust emission test cycle much corresponded with real world conditions.