A modeling framework has been developed to produce detailed emission inventories for large urban areas. Relationships were developed between the time spent in each driving mode (cruise, acceleration, deceleration, and idle) and basic link characteristics based on simulations of selected real-world surface street networks and freeway sections using the TRAF-NETSIM and INTRAS microscopic models, supplemented by field data. These relationships were then incorporated into a specially written computer program as a postprocessor to the Urban Transportation Planning System type of four-step travel demand models. The integrated model was successfully applied to the 1,120-zone Metropolitan Transportation Commission San Francisco Bay Area network to generate vehicle activity estimates.