Analysis of city/transportation system relationship via land consumption

In large cities and dense urban centers, traffic congestion with all its negative consequences is a serious chronic problem. It results from a lack of balance between activities and transport system in terms of their occupancies of limited land. There have been studies about the physical limitations in accommodating auto traffic in a city, but under many assumptions related to activities and greatly simplified transport system. Hence only a partial aspect of the relationships between the activities and the transport system has been analyzed. This study constructs an operational model of a city incorporating interactions between the transportation system and all other activities (housing, economic, social, and other). Activities themselves require a portion of the limited land, and they generate trips that consume the land as well. This causes interdependence between the activities and the transportation system through their land consumption. When the sum of two land requirements is less than the available land, a city can function efficiently. If it exceeds, people move under congested and inefficient conditions, and activities function in crowded conditions, or may be displaced to other areas. The model incorporates the volume and distribution of activities and intensity of land utilization as parameters influencing their land requirements for non-transport use. Particular emphasis is given to the model of transport system: its land requirements depend on modal split, vehicle occupancies, use of parking facilities, as well as activity volume and distribution. The entire model of interrelated land requirements by the activities and by transportation is presented and used for extensive sensitivity analysis. Using time-area measure, land requirement is analyzed as a function of car vs. transit use, car occupancy and other characteristics. Impact of an increase in activities is traced through its increase in direct land requirements and in increased transportation land requirement. Thus, a city is modeled as an integrated set of activities and its transportation system, which interact as a closed system through functional and transportation land requirements. It allows examination of contributions of different parameters to land consumption as well as limits of activities in a city