An analytical method is described for estimating and graphically comparing the amounts of mass emissions from automobiles, buses, commuter trains, and rail transit given the emission characteristics of each type of vehicle. Emissions considered included carbon monoxide (CO), hydrocarbons (HC), nitrogen dioxide (NO2), and sulfur dioxide (SO2). These mass emissions are expressed in “grams per person mile” as well as “grams per vehicle mile” in order to consider their quantity based on the movement of people as well as on the movement of vehicles. The relative effects of these pollutants are also presented.Information from this method can be used to estimate the quantity of emissions produced in a specified area given the travel characteristics of that area. Changes in the amount of emissions resulting from persons who change their mode of travel can also be estimated. An example is used to demonstrate the method and application.Application of this method for a given region can help local officials estimate the effects of various transportation policies on the regional transportation-related pollution. For example, estimated changes in travel habits that result from changes in the transportation system (rail transit, freeway, or busway construction), when combined with the information contained in this publication, can be helpful in estimating-in advance-the impact of various transportation policies as it relates to the amounts of emissions in a given region.