Abstract
A model has been developed to estimate optimal mix of traffic types under environmental constraints in the future. The model constructed is a linear-programming model, where the share of each traffic means among zones is determined so as to minimize the generalized cost obtained as a sum of the trip cost and travel time converted into a money term under various constraints, such as the capacity of each transportation facility and the permissible amount of pollutant emission. By applying to the actual data of the OD survey in 1990 in Osaka, it has been confirmed that the model can explain fairly well the actual situations of modal split among different traffic means. The impacts of policies of imposing control on nitrogen oxide (NOx) emission as well as carbon dioxide (CO2) emission were investigated for Osaka city in the year 2010. It has been shown from scenario analyses using the model that it would be impossible to satisfy the environmental constraints only by reducing unit NOx exhaust coefficient of private car and taxi, and that electric car and natural-gas firing bus should be introduced to the rate of 3.0-3.1% and 0.97-1.2% of the total traffic means, respectively.
