Abstract: Aiming at the problem of traffic congestion in hydro-junction, a navigation improvement strategy that introduces a congestion charging mechanism is discussed. First of all, considering the heterogeneity of dam-passing methods, a dam-passing cost function is established to reflect the transfer patterns of ship passing periods and methods, and based on this, an analysis is made to find what types of ships are the key to alleviating traffic congestion. Secondly, a bi-level programming model is adopted, with the total cost of the dam-passing system and the economic and environmental costs of the ship as the upper and lower optimization targets. The synergistic mechanism of charging for navigable buildings and reducing transportation costs for crossing-dam is explored. Finally, the Three Gorges Project is taken as an example for analysis. The results show that traffic congestion is caused mainly by ships with high cargo capacity, so introducing a toll mechanism can significantly alleviate the traffic congestion, but this will result in an increase in the total cost of the dam-passing system. Crossing-dam transportation can make up for the lack of capacity of the dam, but cannot alleviate the traffic congestion in a certain period of time. The implementation of the coordinated strategy of crossing-dam highway toll reduction and congestion tolling can further control the total cost while increasing navigation efficiency, but the rate of fare reduction must match the passing capacity.

Key words: congestion charge, navigation building, crossing-dam transportation, bi-level programming