Modeling the Effects of Low-carbon Emission Constraints on Mode and Route Choices in Transportation Networks

The primary objective of this study is to understand the effects of the low-carbon constraints on the route and mode choices of trip makers, and their impacts on the performance of a transportation network which is composed of buses and private cars. A combined mode split/traffic assignment model that considered the low-carbon constraints was proposed. The low-carbon constraints considered both the system CO2 reduction constraint and the link CO environmental traffic capacity constraint. The effects of low-carbon constraints were estimated using the equilibrium solution of the proposed combined mode split/traffic assignment model, which was obtained using the generalized lagrangian multiplier solution method. The proposed model was tested in two hypothetical test networks. It was found that by changing the route and mode choices of trip makers the network equilibrium results under the low-carbon constraints can be achieved. Both system travel time and carbon emissions of the congested network can be reduced when low-carbon constraints are used. However, for the non-congested network, the use of low-carbon constraints will increase the system travel time.The proposed model can be directly used by transportation decision makers to evaluate the effects of various policies that focus on limiting low-carbon emissions on the overall performance of the road network.