Accelerated procedure of multiclass highway traffic assignment for Maryland statewide transportation model

The Maryland Statewide Transportation Model (MSTM) under development contains 20 user classes in the highway assignment procedure, including three types of autos: single-occupancy vehicles (SOV), high-occupancy vehicles (HOV) with two passengers, and HOV with three or more passengers classified by five income levels: commercial vehicle, median trucks, heavy trucks, regional autos, and regional trucks. A comprehensive disaggregation of user classes aids in capturing differences in how the transportation network is used. For example, SOV drivers are not allowed to use HOV lanes; trucks cannot be driven on truck-prohibited lanes; drivers at various income levels make different decisions about using toll roads because of their different values of time. However, a large number of user classes impose substantial computational burden on the procedure of multiclass highway assignment. If the conventional algorithm is used, the time consumption for this procedure is approximately proportional to the total number of user classes. In this study, a novel algorithm proposed by Robert Dial in 2006 is used to transfer min-path trees from one user class to another in the procedure of multiclass traffic assignment. This algorithm made it possible to speed up the highway assignment procedure of MSTM by a factor of 5.87.