بازپرداخت هزینه ها، تاثیرات زیست محیطی و سطوح خدمات در طراحی مطلوب ناوگان حمل و نقل اتوبوس

We apply the framework to support design of bus fleets consisting of 4 bus types differing in their fuel-propulsion technology: ultra-low sulfur diesel, hybrid diesel-electric, compressed natural gas, and hydrogen fuel-cell. The 4 bus types were assessed in the National Renewable Energy Laboratory transit bus evaluation and demonstration studies conducted over the period 2003-2009. The nominal problem herein is to minimize acquisition, operation and disposal costs. Constraints in the model are used to impose a minimum frequency of service, i.e., headway, and to ensure that route capacity satisfies passenger demand. Environmental impact is considered along the following dimensions: energy consumption, and emissions of greenhouse gasses, particulate matter, and nitrous oxides. Results show that fleet heterogeneity increases in scenarios where demand fluctuates, i.e., peak vs. off-peak. Perhaps even more interesting, we show how the dual/shadow prices provide a (monetary) measure of the tradeoffs among level of service and environmental impact, and discuss how they can be used to obtain robust fleet configurations.