International audienceThis paper studies the implication of aggregating establishments by categories with different levels of detail for modeling urban freight trip generation. To this effect, the authors use a dataset of 2.970 establishments collected in 1998-1999 in France to conduct a formal assessment of FTG patterns homogeneity inside the traditional activity-based grouping (retail, manufacturing, wholesale, etc.). The results shows that, although, for some categories the traditional high-level aggregation includes sub-sectors with homogenous FTG patterns and thus produces appropriate models; in some other cases (e.g., retail, manufacturing), the sub-sectors have different FTG patterns and thus more detailed data is needed to calibrate...