On-road vehicles are a key source of air pollution in metropolitan areas. Transportation planners and policy makers are confronted with the impacts of transportation on air quality. They require a tool to quantify the environmental effects of planned transportation control and urban development measure and thus aid in selecting the most suitable projects. This book describes the development of CALMOB6 - a tool to estimate emissions and fuel consumption effects of proposed developments or regulations before they are implemented. The model incorporates twenty-one vehicle sub-classes. On a second-by-second basis, CALMOB6 calculates emission rates of carbon monoxide, nitric oxides, hydrocarbons, particulates and carbon dioxide, as well as the fuel consumption rates for vehicles operating in an urban region. It can forecast these quantities till year 2050. CALMOB6 considers effects of alternative fuels, vehicle fleet, cold-starts, super-emitters and environmental conditions. The tool can produce an inventory on scales varying from an entire urban region down to a single identified street at a single operating time-scale. This book is addressed to professionals in transportation and environment.