Turn-based algorithm for Logit traffic assignment

To overcome the shortcomings in traditional network-expanding method for handling turn delays in traffic assignment, a turn-based algorithm for Logit traffic assignment was developed with a similar framework of Dial algorithm, which was based on the topological relationships between network element nodes, links and turns. According to the origin-to-link-type shortest path distances with turn delays, all links were processed, turn weights were computed forward, and link flows and turn flows were assigned backward by the algorithm. Computation result shows that the flow assignment of the algorithm is identical to Logit-based path flows and Dial's algorithm data, the algorithm directly computes link flow and turn flow patterns, which not only agrees with Logit route-choice probability, but also counts for the effect of turn delays on traffic assignment, and Dial algorithm is a special case of the algorithm when all turn delays vanish.