Time Use and Activity Systems

Time use studies clearly document that human activities do not occur in a vacuum. Each individual activity is part of a spatial, temporal socio-economic system. Each activity is part of a system of activities that integrates and facilitates ongoing day-to-day behavior and it is inextricably linked to other activities, past, present and future. Cooperatively and/or independently, individuals and groups interact and make opportunity-changing choices impacting, at various levels, the activity systems of which they are a part. Unfortunately, the four-step approach, which for so long dominated transportation planning, failed to recognize this reality. A mechanistic approach that ignored the spatial, temporal, and individual interdependencies among transportation, land use, and population, it has left a legacy of urban areas with seriously inappropriate land use and transportation systems. The aggregate approach of the method to planning failed, to providing the guidance necessary to plan efficient, equitable, and sustainable land use and transportation systems. Fortunately, major shortcomings of the four-step approach are being overcome by a shift in thinking toward an activity-based planning approach. This chapter explores the development of activity-based planning and activity systems, identifies and elucidates activity-related data needs, and it discusses the important role and method of time use studies in supply such data.