Computational Tools for Measuring Space-Time Accessibility within Transportation Networks with Dynamic Flow

The space-time prism (STP) and STP-based accessibility measures are powerful techniques for assessing the ability of individuals to travel and participate in activities at different locations and times in a given environment. However, traditional STPs and STP-based accessibility measures ignore spatial and temporal variations in travel times in an urban environment. Factors such as traffic congestion impose increasingly complex and severe constraints on individual travel and activity participation. This paper reports on the development of dynamic STP-based accessibility measures and computational procedures for accessing individual accessibility in networks with time-varying flow. We extend static network-based STPs to the case where network flow and travel velocities vary across time due to congestion. These tools can evaluate the accessibility of travelers under different levels of traffic congestion, alternative network flow control strategies and activity scheduling policies (e.g., flextime and telecommuting).