Real-road NO_x and CO₂ emissions of city and highway China-6 heavy-duty diesel vehicles

The emission of heavy-duty vehicles has raised great concerns worldwide. The complex working and loading conditions, which may differ a lot from PEMS tests, raised new challenges to the supervision and control of emissions, especially during real-world applications. On-board diagnostics (OBD) technology with data exchange enabled and strengthened the monitoring of emissions from a large number of heavy-duty diesel vehicles. This paper presents an analysis of the OBD data collected from more than 800 city and highway heavy-duty vehicles in China using remote OBD data terminals. Real-world NO_x and CO₂ emissions of China-6 heavy-duty vehicles have been examined. The results showed that city heavy-duty vehicles had higher NO_x emission levels, which was mostly due to longer time of low SCR temperatures below 180°C. The application of novel methods based on 3B-MAW also found that heavy-duty diesel vehicles tended to have high NO_x emissions at idle. Also, little difference had been found in work-based CO₂ emissions, and this may be due to no major difference were found in occupancies of hot running.