Space-time accessibility measures within dynamic transportation networks

Individuals' lives are constructed by daily activities. The accessible spaces and available times constrain individuals' ability of where and when to participate in activities. Urban transportation systems exist to alter the relationship between space and time. Most transportation models are focused on maximizing traffic volume. However, activity participation is more important than travel itself. Space-time accessibility measures are alternative approaches to evaluate individuals' freedom for activity participation. Traditional space-time accessibility measures assume uniform and static environments. Travel conditions vary with space and time in environments due to network structure and traffic congestion. The spatial and temporal complexities of transportation systems impose severe constraints on individual's travel behaviors. The fundamental objective of this research is to expand space-time accessibility measures within time-dependent transportation networks.; A prototype of Dynamic Space-Time Accessibility Measures (DSTAM) system is built within Geographic Information Systems (GIS) environments. It contains several modules. A Dynamic User Optimal (DUO) model simulates time-dependent traffic flow. The Dynamic Route Planner (DRP) module generates different types of query results for time-dependent shortest paths. Two space-time accessibility measures are proposed in this research. Dynamic Network Time Prism (DNTP) is an accessibility measure directly extending from space-time prism concepts. It defines maximum accessible travel planar area under a limited time budget and can delimit the activity choice set for accessibility benefit measures. Dynamic space-time Accessibility Benefit Measures (DABM) incorporates three complementary views of accessibility measures: space-time prism, attraction-accessibility, and benefit measure approaches. These measures not only use the constraint approach to limit the individual travel choice but also provide a quantitative measure of individual benefits.; The DUO module can be a planning tool for road closure due to planned constructions or accidents. The DRP module can serve as a realistic optimal route decision support system. DABM can provide an efficient tool in real estate analysis and serve as urban development tools. DNTP have potential to support the measurements and analytical functions for wireless location-based services. The analysis results from this prototype of DSTAM-GIS system provide more insights of dynamic traffic environments for further time geography research.