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91.
We build a duopoly model to shed light on the environmental impact of HSR-air transport competition, capturing the effects of induced demand, schedule frequency and HSR speed. The net environmental effect can be negative since there is a the trade-off between the substitution effect – how many passengers using the HSR are shifted from air transport – and the traffic generation effect – how much new demand is generated by the HSR. We conduct a simulation study based on the London-Paris market where HSR has served 70% of the market. The introduction of HSR is detrimental to LAP, while it is beneficial to GHG emissions. HSR entry increases neither LAP nor GHG emissions when the ratio between HSR and air transport emissions is relatively low. Moreover, competition is more likely to be detrimental to the environment when the weight of the social welfare in HSR objective function is high. Since the magnitude of the environmental friendliness of HSR compared to air transport hinges on the mix of energy sources used to generate the electricity (which is heavily constrained by the country in which HSR operates), regulators should assess the implications of HSR entry taking into account the energy policy and mitigation strategies available to transport modes. 相似文献
92.
As decision-makers increasingly embrace life-cycle assessment (LCA) and target transportation services for regional environmental goals, it becomes imperative that outcomes from changes to transportation infrastructure systems are accurately estimated. Greenhouse gas (GHG) reduction policies have created interest in better understanding how public transit systems reduce emissions. Yet the use of average emission factors (e.g., grams CO2e per distance traveled) persists as the state-of-the-art masking the variations in emissions across time, and confounding the ability to accurately estimate the environmental effects from changes to transit infrastructure and travel behavior. An LCA is developed of the Expo light rail line and a competing car trip (in Los Angeles, California) that includes vehicle, infrastructure, and energy production processes, in addition to propulsion. When results are normalized per passenger kilometer traveled (PKT), life-cycle processes increase energy use and GHG emissions up to 83%, and up to 690% for smog and respiratory impact potentials. However, the use of a time-independent PKT normalization obfuscates a decision-maker’s ability to understand whether the deployment of a transit system reduces emissions below a future year policy target (e.g., 80% of 1990 emissions by 2050). The year-by-year marginal effects of the decision to deploy the Expo line are developed including reductions in automobile travel. The time-based marginal results provide clearer explanations for how environmental effects in a region change and the critical life-cycle processes that should be targeted to achieve policy targets. It shows when environmental impacts payback and how much reduction is achieved by a policy-specified future year. 相似文献
93.
The purpose of this paper is to explore themes and challenges in developing environmentally sustainable logistical activities.The approach is explorative with a cross sectional design that takes advantage of ten case studies out of selected logistics service providers (LSPs) operating primarily in the Scandinavian countries.The findings illustrate the major themes by analyzing current and future activities in developing environmentally sustainable logistical activities. In addition, four categories of challenges are identified: customer priorities, managerial complexity, network imbalance, and technological and legislative uncertainties. It is concluded that there is a great need for a holistic perspective where LSPs and product owners together analyze and design future logistical setups.The suggested holistic and integrative model, building on a three-dimensional concurrent engineering framework, provides new opportunities for research. Further research is needed to improve the interrelationship between LSPs and their customers in the development of sustainable logistical solutions.This paper puts forward recommendations for the sustainable development of logistics by combining the results from the case studies with a review of related literature. This will be beneficial for managers and policy makers when they approach sustainable logistical challenges. The emergence and synthesis of themes and challenges are critical for a sustainable society. 相似文献
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介绍ZD(J)9型电动转辙机在振动试验中表示杆的约束和自动开闭器开闭状态存在的问题,以及转辙机在运用过程中低温环境下结霜和防水性能差等问题。根据转辙机工作原理,提出相应改进措施,有效地解决了上述问题。 相似文献
97.
A model to estimate and compare the ecological impact and economic feasibility of a land transportation system (trucks) and
a marine transportation system (cargo ships) was developed and presented in a previous report.1 Three different comparison indices—environmental, economic, and customer service—were used to evaluate and compare their
ecological impacts and determine their economic superiority. In this article, a single comparison index is proposed and assessed
for the two transportation systems. The estimates were made for nine different routes in Japan. A simple mathematical model
of the whole methodology is given. The sensitivity of the weighting factors used in the comparison method was analyzed. The
social cost saving in monetary terms through a modal shift is also presented.
Received: February 15, 2001 / Accepted: September 19, 2001 相似文献
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青藏铁路建设的生态环境保护 总被引：1，自引：0，他引：1
青藏铁路格拉段建设中,为有效控制工程建设对沿线生态环境的影响,维持高原生态系统的自我平衡,对环境保护工作实施了全面系统化的管理和一系列技术创新。从项目的可行性研究,到设计、施工,每一环节都贯彻环保理念,充分体现了“预防为主、保护优先、开发与保护并重”的原则,全面创新了施工期间的环保管理模式,环境保护取得了显著的成效。青藏铁路建设的环保实践表明,积极探索环保施工方法和工艺,切实落实环保措施、科研和技术创新等,为做好环境保护提供了重要保证。 相似文献
100.