A modified version of the ISMAP model has been developed for the analysis of carbon monoxide hot spot locations. The original version of ISMAP (Indirect Source Model for Air Pollution) was developed by Stanford Research Institute to be used in the evaluation of indirect source impact upon ambient carbon monoxide concentrations. Due to the size and complexity of the original version of the model, the modifications were made without changing the basic structure of the program. Since the analysis of parking lot traffic and emissions was an integral part of the original model structure, it was left in the modified version, but the code was modified to negate their effect upon traffic flow and air quality. In the modified ISMAP, internal zones (indirect sources) are used together with external zones to generate flow within a traffic network. This modified version of the model sets parking lot emissions equal to zero and provides a near infinite parking lot capacity so that vehicle routing between internal zones will not occur because of parking lot overcrowding. Other modifications made to ISMAP include the incorporation of a street canyon submodel. Version 2 of modified ISMAP utilized the most recent (1978) motor vehicle emission correction factors and modal analysis model coefficients and deterioration. In other aspects, it is unchanged from Version 1.