Exhaust Emissions Testing on the Highway—New!

In the preliminary study (BASt Report F 159), remote-sensing measurements were conducted on a German highway for the first time in 2022. The analysis revealed significantly higher NOx emissions from trucks than the values suggested by the HBEFA 4.2 manual. The current project is investigating, in five steps, why the measured emissions are so high and how they align with the average HBEFA factors:

• Cleaning the remote-sensing data of erroneous values and outliers
• Comparison with measurements from other European highways
• Comparison with HBEFA 4.2, taking vehicle age and traffic conditions into account
• PHEM simulation (Passenger Car and Heavy-Duty Emission Model) for the measurement site
• Drawing conclusions and recommendations for future measurements

The anomalous values result primarily from the specific driving conditions at the measurement site (uphill drive following a prolonged downhill drive), which - particularly for trucks - determine whether the exhaust aftertreatment system has already reached operating temperature and, consequently, how high the NOx emissions in particular are.

The full article is available on the BASt-website.