We modeled annual average PM2.5 concentrations attributable to vehicle emissions in California using the Intervention Model for Air Pollution (InMAP) Source-Receptor Matrix (ISRM) . The ISRM was developed from the United States InMAP, which used WRF-Chem simulations and U.S. Environmental Protection Agency National Emissions Inventory (NEI) emissions estimates for 2014. The national version of InMAP was sampled on a population-weighted, variably-sized grid (n = 21,705; 1 km to 48 km) for the state of California . Approximately 74% of grid cells are the finest resolution, with a population-weighted grid size of 2.4 km (urban: 1.2 km, rural: 7.4 km). The gridding algorithm ensures that no cell larger than 1 km contains more than 20,000 people or a census block group with population density higher than 2,500 people/km. The ISRM relates, for the n = 21,705 grid cells in California, marginal changes in groundlevel concentration in every grid cell to marginal changes in emissions in every cell. Because this work only evaluates impacts from on-road mobile sources, all concentrations were estimated using the ground-level (i.e., 0 -57 m above ground) layer.