Combined Decision Making of Congestion Pricing and Capacity Expansion: Genetic Algorithm Approach

This paper presents a solution methodology that can be used to determine the optimal solution for the combined congestion pricing and capacity expansion problems. A bilevel genetic algorithm (GA)-based optimization solution methodology is proposed to determine the optimal toll location, toll rate, percentage capacity expansion, and location for the expansion simultaneously. The upper-level subprogram minimizes the total system travel cost given certain budget and toll constraints. The lower-level subprogram is a user equilibrium problem where all users try to find the route that minimizes their own travel cost (or time). The budget constraint is handled using a penalty parameter. The demand is assumed to be fixed and given a priori. The proposed GA model is applied to Sioux Falls network, which has 76 links and 24 origin-destination (OD)-pairs, assuming homogeneous users. The optimal solution is thus identified. Sensitivity analyses are conducted for the budget and penalty parameter. The proposed methodology will be a very useful tool for transportation network planners for allocation of budgets and prioritization of links for improvements and congestion pricing.