Characterization of in-use emissions from on-highway heavy-duty diesel engines

Class-8 trucks with GVWR of 80,000 lbs were tested on different driving routes and in-use brake-specific emissions of NOx and CO2 data were collected using the West Virginia University\u27s Mobile Emissions Measurement System (MEMS). An uncertainty analysis was performed on the MEMS and it was determined the maximum possible error in the measurement of brake-specific emissions of NOx was 8% and CO2 was 6%.;A modal analysis indicated that the cruise mode comprised 70% of the time that the vehicle spent in the Not-to-Exceed (NTE) zone while the acceleration and deceleration modes about 20% and 10% respectively.;In order to reduce the uncertainties in emissions measurement, it is proposed that fuel specific NOx, a ratio NOx /CO2 be used for emissions compliance purposes. The values of the proposed ratio were found to vary from 1.17 to 1.83 depending upon engine model, model year, manufacturer and the driving route