Formulation and solution method of bounded path size stochastic user equilibrium models – consistently addressing route overlap and unrealistic routes

Bounded Path Size (BPS) route choice models (Duncan et al, 2021) offer a theoretically consistent and practical approach to dealing with both route overlap and unrealistic routes. It captures correlations between overlapping routes by including correction terms within the probability relations, and has a consistent criterion for assigning zero probabilities to unrealistic routes while eliminating their path size contributions. The present paper establishes Stochastic User Equilibrium (SUE) conditions for BPS models, where the choice sets of realistic routes are equilibrated along with the route flows. Solution existence/uniqueness are addressed. A generic solution algorithm is proposed, where realistic route choice sets are equilibrated from a pre-generated approximated universal set of routes. Numerical experiments on the Sioux Falls and Winnipeg networks show that BPS SUE models can be solved in feasible computation times compared to nonbounded versions, while providing potential for significantly improved robustness to the adopted master route choice set.