Top: Normalized diurnal profiles of Vehicle Miles Traveled (VMT) by vehicle class (light duty (LD), medium duty (MD), heavy duty (HD)) for Mondays and Fridays. Bottom: Diurnal profile of winter NO_x scale factors from the Multiple Linear Regression (MLR) model; bar chart showing the contribution of each vehicle class to a diurnal profile with the best match to the NO_x scale factors. The percentage contribution of each vehicle class and the correlation coefficient between the sum of the VMT profiles and the NO_x scale factors are shown inside the legend. DOI: https://doi.org/10.1525/elementa.384.f5