When heavy-duty truck emissions are expressed in distance-specific units (such as g/mile), the values may depend strongly on the nature of the test cycle. Prior studies have compared emissions gained using different cycles and have proposed techniques for translating emissions factor rates between cycles. First, emissions data from the 5-mode CARB HHDDT Schedule, UDDS, and AC5080 were reviewed, with reference to each other. NO X and PM emissions were the two components of emissions reviewed. A heavy-duty chassis dynamometer was used for emissions characterization along with a full scale dilution tunnel. The vehicle test weights were simulated at 30,000 lbs, 56,000 lbs, and 66,000 lbs. For each vehicle, average data from one cycle have been compared with average data for a different cycle. When the Cruise mode and Transient mode of the HHDDT schedule were compared, it was evident that injection timing strategies affected the average Cruise mode emissions of NO X. As a result, there was substantial data scatter when mode-averaged Cruise emissions were plotted against mode-averaged Transient emissions. Moreover, the relationship between Cruise and Transient NO X was not the same for the various test weights. Correlations for PM varied widely in goodness of fit to the data. This is because PM may increase substantially due to elemental carbon "puff" which occurs when the turbocharger has not reached full boost pressure at the onset of an increase in engine load. The AC5080, originally developed for inspection and maintenance applications, showed reasonable correlation with the UDDS, although a best fit line still caused the AC5080 to mis-predict 16 out of 25 UDDS NO X values by over 20%. It was concluded that information is needed on both the transient and steady high speed emissions characteristics of a vehicle before an emissions factor can be estimated for a road link. Next, two-dimensional correlations were used to predict the emissions rate on one cycle from the rates of two other cycles. The vehicle test weights were simulated at 56,000 lbs. The multidimensional analysis using two cycles yielded better predictive correlations for the emissions than single cycle correlations. The UDDS yielded the highest distance-specific emissions and it showed similar emissions as the combination of the Cruise mode and Transient mode of the HHDDT. Weight, like transients, significantly effects the emissions of a vehicle. Its effect is different for different species. The emission of NO X , CO, CO 2 , HC and PM were analyzed with respect to weight. There were three types of vehicles analyzed: HHDDT, MHDDT and MHDGT. These Kuntal A. Vora Cycles and Weight Effects on Emissions and Development of Predictive Emissions Models for Heavy Duty Trucks v 2. Acknowledgments