Energy issues in transportation systems have garnered increasing attention in recent years in both thepublic and private sectors. This study proposes a systematic methodology for policy-makers to improveenergy consumption efficiency in multimodal intercity transportation systems considering suppliers’operational constraints and travelers’ mobility requirements. A bi-level optimization model is developedfor this purpose and considers the air, rail, private auto, and transit modes. The upper level model is amixed integer nonlinear program that aims to minimize energy consumption subject to transportationsuppliers’ operational constraints and the traffic demand distribution to paths resulting from the lowerlevel model. The lower level model is a linear program that seeks to maximize the intercity trip utilities oftravelers. The interactions between the multimodal transportation suppliers and intercity traffic demandare considered under the goal of minimizing energy consumption at the system level. The proposed bilevelmixed integer nonlinear model is relaxed and transformed into a mathematical program withcomplimentarity constraints, and solved using a customized branch-and-bound algorithm. Numericalexperiments, conducted using multimodal travel options between Lafayette, Indiana and Washington, D.C.reiterate that shifting traffic demand from private cars to the transit and rail modes can significantlyreduce energy consumption. More importantly, the proposed methodology is able to provide quantitativeanalyses for system energy consumption and traffic demand distribution among transportation modesunder specific policy instruments. The results also illustrate the need to systematically incorporate theinteractions between traveler preferences, network structure, and supplier operational schemes to providepolicy-makers insights for developing traffic demand shift mechanisms to minimize system energyconsumption. Hence, the proposed methodology can provide policy-makers the ability to analyze energyconsumption in the transportation sector under different policy instruments.
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