Selection bias in build-operate-transfer transportation project appraisals

Recent empirical studies have found widespread inaccuracies in traffic forecasts despite the fact that travel demand forecasting models have been significantly improved over the past few decades. We suspect that an intrinsic selection bias may exist in the competitive project appraisal process, in addition to the many other factors that contribute to inaccurate traffic forecasts. In this paper, we examine the potential for selection bias in the governmental process of Build-Operate-Transfer (BOT) transportation project appraisals. Although the simultaneous consideration of multiple criteria is typically used in practice, traffic flow estimate is usually a key criterion in these appraisals. For the purposes of this paper, we focus on the selection bias associated with the highest flow estimate criterion. We develop two approaches to quantify the level and chance of inaccuracy caused by selection bias: the expected value approach and the probability approach. The expected value approach addresses the question “to what extent is inaccuracy caused by selection bias?”. The probability approach addresses the question “what is the chance of inaccuracy due to selection bias?”. The results of this analysis confirm the existence of selection bias when a government uses the highest traffic forecast estimate as the priority criterion for BOT project selection. In addition, we offer some insights into the relationship between the extent/chance of inaccuracy and other related factors. We do not argue that selection bias is the only reason for inaccurate traffic forecasts in BOT projects; however, it does appear that it could be an intrinsic factor worthy of further attention and investigation.     

南京地铁宁溧线信号控制4/6节编组列车混合运行技术方案

根据南京地铁宁溧线和机场线贯通运营的要求,空港新城江宁站至无想山站小交路需要支持4/6节编组列车混合运行.为此,信号系统需对车载信号和轨旁信号进行特殊设计,除在轨旁增加混合运行控制设备,并配置不同的车载数据库,实现自动识别列车编组外,还需对不同编组列车的定位、超速防护、对标停车、试车线测试以及站台门联动进行设计,增加混合运行功能,实现4/6节编组列车的安全运行控制.     

IMO自愿审核机制在航标领域的审核及对策研究

近年来,国际海事组织（IMO）为了促进国际海上安全和海洋环境保护公约的有效实施,于2006年开始推行“IMO成员国自愿审核机制”。文中第一部分分析了该机制的产生原因和运作过程;第二部分分析了该机制的实施可能给中国带来的影响;第三部分根据SOLAS公约和IALA建议提出了审核机制在航标管理方面的审核内容;在最后一部分通过对中国航标管理现状的分析,尝试性地提出了几个对策性建议。     

道路“白改黑”方案及工程造价分析

2007年以前修建的水泥混凝土道路,经多年运营,其路面质量明显下降,部分已遭到损坏,已满足不了日益增长的交通流量的需要,需改造成性能优良的黑色沥青路面。此文在阐述道路白改黑工程特点的前提下,论述影响道路白改黑工程造价的主要因素。并结合工程实例,对可采取的改造方案进行比较,对有关工程造价及指标进行分析,提出推荐方案。     

Developing a Sustainable Community-Based Aquaculture Plan for the Lagoon of CuyutlÀn through a Public Awareness and Involvement Process

This study presents evidence from the Cuyutlàn lagoon, which demonstrates that aquaculture can be socially acceptable, economically viable and environmentally friendly when consideration is first taken of the local circumstances and environment. This evidence was obtained through a user survey, which asked key questions of the local fishing community. These questions aimed to determine the desires and needs of the local community in the context of the local environment. The results from this survey of 56% of the fishing community were presented. The wishes of the fishing community are discussed and a compromise suggested for a sustainable aquaculture for the Cuyutlàn lagoon.     

基于多智能体的城市轨道交通列车延误仿真模型与应用

城市轨道交通列车延误处置方案制定是轨道交通运营管理的重要工作,处置方案的合理性是提高处置效率的前提,验证处置方案的合理性也是运营管理部门急待解决的问题。基于此,以多智能体（以下简称多Agent）理论为基础,分别构建乘客Agent、列车Agent、网络Agent及突发事件Agent的仿真模型;分析列车延误的多Agent仿真原理;以上海轨道交通2号线列车延误为背景,编写多Agent列车延误仿真程序,并对处置方案进行仿真分析,该模型已在上海轨道交通人民广场站大客流处置工作中得到了实际应用。     

滨港铁路沾化至滨州港段接轨方案研究

滨港铁路沾化至滨州港段是滨港铁路的二期工程,拟在一期工程终点站沾化站附近接轨。由于沾化站的位置、站型等特殊条件,使接轨方案的选择成为影响线路总体方案的重要因素。通过研究主要货流方向、接轨站条件、工程费及运营费、城市规划等诸多因素,结合线路走向的选择,经过技术经济比选,最终确定合理的接轨方案。     

怀邵衡铁路复杂不良地质区域线路方案研究

由于怀邵衡铁路在怀化南客站至安江站段存在铀矿、岩溶、断层等多种复杂不良地质,线路方案比选影响因素复杂,方案选择困难,采用地质条件分析及工程经济技术比较等方法,详细论述铀矿辐射、岩溶及岩溶水、断裂构造、高地应力、页岩气、围岩分级、工程投资、工期等因素对该段方案选择的影响,通过综合分析各种地质及工程经济技术条件,最终确定西线方案为合理的线路方案。     

基于SE-DEA的城市轨道交通线网规划方案优选

城市轨道交通线网规划初始方案的选择是城市规划者与建设者应予以重视的关键问题。针对已有研究方法中所存在的不足,提出一种基于超效率数据包络分析(SE-DEA)的轨道交通线网方案比选方法,构建城市轨道交通线网方案的综合评价指标体系并有效筛选出决策单元的输入输出指标。结合某市轨道交通线网规划方案进行实证研究,模型所测结果与该市主推线网方案一致,验证方法的可行性与有效性。所提出的方法依据方案间的相对效率,对预选方案进行优劣性排序,可为城市管理者提供决策依据。     

高速铁路开行17辆编组动车组信号系统方案研究

根据开行17辆编组动车组信号系统的需求,通过分析部分高铁设计方案,并对3种优化设计方案进行对比,希望提出的建议能对高速铁路设计工作提供帮助.