Validation of Link Proportionality Assumptions Accounting for Day- To-day Variability

Transport systems are inherently uncertain, posing a challenge to network modellers and planners. Newer models (probabilistic user equilibrium, strategic user equilibrium) attempt to capture this uncertainty by explicitly acknowledging day-to-day randomness in the network, and solve for strategic equilibrium conditions based on the concept of travellers optimizing their expected performance. Strategic models are based on the assumption that the realized conditions on each network link vary proportionally with network-wide variation. While intuitive, this assumption is yet to be validated. Therefore, the objective of this work is twofold; to use observed network conditions to quantify the day-to-day variability and to validate the link proportionality assumption intrinsic to the novel strategic traffic assignment models. The analysis is conducted using measured 15-minute flows on a simple corridor-shaped network in Sydney, Australia. We find that day-to-day variation dominates time-of-day variation, and that variation in link demand can be explained by changes in network demand.