We developed and employed an open-source analysis method based on atmospheric simulations from the Intervention Model for Air Pollution (InMAP, see Methods) to model total PM2.5 concentrations resulting from emissions of PM2.5, NOx, VOC, NH3, and sulfur oxides (SOx) emitted by California's on-road mobile source sector from 2000 to 2019. Estimates of onroad mobile emissions are from CARB's Emission FACtor regulatory model (EMFAC v2021 with MPOv11), which has been approved by the U.S. EPA . EMFAC represents CARB's best estimate of on-road emissions; it incorporates detailed administrative and observational data pertaining to fleet composition, emissions performance, and spatiotemporal activity patterns . Variably sized gridded PM2.5 concentrations (1 km -48 km, higher resolution in greater population density locations) are combined with tract-level 2010 Census population data to estimate exposure disparities among demographic groups . We disaggregate mobile source impacts into four vehicle types: LDV, MDV, HDV, and all other vehicles (e.g., buses, motorcycles, motorhomes; Table ).