In order to improve the accuracy of the NOx emission estimation for city heavy-duty refuse trucks, this paper presents an operating mode-based NOx emission model for heavy-duty refuse trucks. First, the VSP bins were defined based on the operating conditions and the emission characteristics of NOx derived from the analysis of second- by- second field speed data for fully loaded and empty heavy- duty refuse trucks respectively. Then, combined with the instantaneous speed of trucks, an operating mode binning method was developed and emission factors for trucks were estimated, which were subsequently compared with the results based on the MOVES model. It is shown that the emission factors of NOx are higher for empty loaded trucks at the low speed level of ([0, 20) km/h) than that of fully loaded trucks, and lower in other speed levels. However, emission factors of NOx estimated based on the MOVES model are lower on all speed levels for both fully and empty loaded trucks than those based on the NOx emission model proposed in this paper. For empty loaded trucks, the differences are found as much as 24.67%, 6.82% and 23.81% at the low speed level ([0，20) km/h), medium speed level ([20，50) km/h) and high speed level ([50，+∞) km/h) respectively. For fully loaded trucks, the differences are 12.38%, 18.81% and 26.43% respectively.
