This study outlines a model that allows transportation planners to quantitatively assess the potential fuel consumption and emission impacts that different investments in transportation infrastructure may have. For example, plans for upgrading a transportation corridor may include alternatives such as additional lanes, increased bus service, or a light rail transit line running parallel to the roadway. With this model, the fuel consumption and emissions resulting from each scenario could be determined and compared to the baseline case (the corridor in its current configuration). The potential benefits resulting from each scenario can then be weighed relative to its cost to ensure that available funding is spent on projects that provide the greatest environmental return on investment. Sample results investigating the greenhouse gas emission reduction potential of an accelerated fleet replacement program and of light rail transit investment in a transportation corridor are presented to illustrate potential applications of the tool.