Land Consumption Impacts of a Transportation System on a City

Abstract

The impacts of a changing transportation system on land consumption are analyzed. An analytical model with which to examine the intrinsic relationships between the volume of activities, the intensity of land use, and the modal split of generated trips is formulated on the basis of an idealized urban region that contains a city within radius R. The city land consists of that required for transportation and that for all other activities. Given hypothetical initial conditions, impacts of an increasing auto modal split are analyzed on the basis of three conceivable strategies to deal with the pressure to expand transportation facilities. The analysis shows that the modal split has a strong influence on volume of activities and land use intensity. A policy of infrastructure expansion to accommodate the increasing number of autos reduces the amount of land available for more fundamental activities that transport is intended to support, not displace. To prevent this displacement, land intensity of areas used for all other activities must increase. Otherwise, the options would be to relocate some activities from the city to outlying areas; such relocation could result in increasing traffic volumes in the entire region. Alternatively, the accommodation of other activities may encroach on previously protected or undevelopable land and lead to unsustainable development for the region. It is also shown that to maintain sustainability of a city, high-capacity transit modes with reserve capacity, such as rail transit systems, represent an efficient option in dense urban areas.