A Probabilistic Model of the Economic Risk to Britain's Railway Network from Bridge Scour During Floods

Scour (localized erosion by water) is an important risk to bridges, and hence many infrastructure networks, around the world. In Britain, scour has caused the failure of railway bridges crossing rivers in more than 50 flood events. These events have been investigated in detail, providing a data set with which we develop and test a model to quantify scour risk. The risk analysis is formulated in terms of a generic, transferrable infrastructure network risk model. For some bridge failures, the severity of the causative flood was recorded or can be reconstructed. These data are combined with the background failure rate, and records of bridges that have not failed, to construct fragility curves that quantify the failure probability conditional on the severity of a flood event. The fragility curves generated are to some extent sensitive to the way in which these data are incorporated into the statistical analysis. The new fragility analysis is tested using flood events simulated from a spatial joint probability model for extreme river flows for all river gauging sites in Britain. The combined models appear robust in comparison with historical observations of the expected number of bridge failures in a flood event. The analysis is used to estimate the probability of single or multiple bridge failures in Britain's rail network. Combined with a model for passenger journey disruption in the event of bridge failure, we calculate a system‐wide estimate for the risk of scour failures in terms of passenger journey disruptions and associated economic costs.     

Assessing Engineering Resilience for Systems with Multiple Performance Measures

Recently, efforts to model and assess a system's resilience to disruptions due to environmental and adversarial threats have increased substantially. Researchers have investigated resilience in many disciplines, including sociology, psychology, computer networks, and engineering systems, to name a few. When assessing engineering system resilience, the resilience assessment typically considers a single performance measure, a disruption, a loss of performance, the time required to recover, or a combination of these elements. We define and use a resilient engineered system definition that separates system resilience into platform and mission resilience. Most complex systems have multiple performance measures; this research proposes using multiple objective decision analysis to assess system resilience for systems with multiple performance measures using two distinct methods. The first method quantifies platform resilience and includes resilience and other “ilities” directly in the value hierarchy, while the second method quantifies mission resilience and uses the “ilities” in the calculation of the expected mission performance for every performance measure in the value hierarchy. We illustrate the mission resilience method using a transportation systems‐of‐systems network with varying levels of resilience due to the level of connectivity and autonomy of the vehicles and platform resilience by using a notional military example. Our analysis found that it is necessary to quantify performance in context with specific mission(s) and scenario(s) under specific threat(s) and then use modeling and simulation to help determine the resilience of a system for a given set of conditions. The example demonstrates how incorporating system mission resilience can improve performance for some performance measures while negatively affecting others.     

大宗物资集中采购的调运计划研究

大宗物资调运问题是一个受多因素影响的复杂问题,一般来讲,其调运数量大、地域跨度大、时间紧。如何协调供需以及运输能力,保证物资采购部门的经济利益是本文所要研究的问题。本文首先给出了大宗物资集中采购的调运模式,然后针对采购部门在大宗物资调运过程中遇到的困难,为采购部门提出了以获取数量折扣、准时采购、降低库存成本和协调运输能力为准则的调运计划模型。数值计算表明应用本文所建模型编制调运计划能够达到降低采购费用、协调运输能力的目的,为大宗物资调运计划的编制提供了一种较为有效的方法。     

Quantitative Methods for Environmental Justice Assessment of Transportation

Application of Executive Order 12898 to risk assessment of highway or rail transport of hazardous materials has proven difficult; in general, the location and conditions affecting the propagation of a plume of hazardous material released in a potential accident are unknown. Therefore, analyses have only been possible in a geographically broad or approximate manner. The advent of geographic information systems and development of software enhancements at Sandia National Laboratories have made kilometer-by-kilometer analysis of populations tallied by U.S. Census blocks along entire routes practicable. Tabulations of total or racially/ethnically distinct populations close to a route, its alternatives, or the broader surrounding area, can then be compared and differences evaluated statistically. This article presents methods of comparing populations and their racial/ethnic compositions using simple tabulations, histograms, and chi-square tests for statistical significance of differences found. Two examples of these methods are presented: comparison of two routes and comparison of a route with its surroundings.     

Risk Analysis of Safety Service Patrol (SSP) Systems in Virginia

The transportation infrastructure is a vital backbone of any regional economy as it supports workforce mobility, tourism, and a host of socioeconomic activities. In this article, we specifically examine the incident management function of the transportation infrastructure. In many metropolitan regions, incident management is handled primarily by safety service patrols (SSPs), which monitor and resolve roadway incidents. In Virginia, SSP allocation across highway networks is based typically on average vehicle speeds and incident volumes. This article implements a probabilistic network model that partitions “business as usual” traffic flow with extreme‐event scenarios. Results of simulated network scenarios reveal that flexible SSP configurations can improve incident resolution times relative to predetermined SSP assignments.     

Monte Carlo Sensitivity Analysis of Unknown Parameters in Hazardous Materials Transportation Risk Assessment

The US Department of Transportation was interested in the risks associated with transporting Hydrazine in tanks with and without relief devices. Hydrazine is both highly toxic and flammable, as well as corrosive. Consequently, there was a conflict as to whether a relief device should be used or not. Data were not available on the impact of relief devices on release probabilities or the impact of Hydrazine on the likelihood of fires and explosions. In this paper, a Monte Carlo sensitivity analysis of the unknown parameters was used to assess the risks associated with highway transport of Hydrazine. To help determine whether or not relief devices should be used, fault trees and event trees were used to model the sequences of events that could lead to adverse consequences during transport of Hydrazine. The event probabilities in the event trees were derived as functions of the parameters whose effects were not known. The impacts of these parameters on the risk of toxic exposures, fires, and explosions were analyzed through a Monte Carlo sensitivity analysis and analyzed statistically through an analysis of variance. The analysis allowed the determination of which of the unknown parameters had a significant impact on the risks. It also provided the necessary support to a critical transportation decision even though the values of several key parameters were not known.     

伦敦立体交通对大西安战略规划的启示

为解决大西安交通发展与城市空间结构优化的问题,梳理伦敦立体交通的构建过程,总结了伦敦交通对城市空间形态的作用机理,并运用Roxy指数模型分析了大西安城市空间形态演化发展的趋势,对大西安交通战略规划提出了发展方向。分析认为：建立一体化的立体交通格局是大西安城市综合交通发展的必经之路,也是实现城市空间结构优化调整的必要手段。     

基于人工神经网络的中原铁路货运向现代物流拓展的对策研究

根据中原铁路货运的现状和自身优势,结合国内外市场需求变化和现代物流发展趋势,运用现代物流原理,分析论证了中原铁路运输业拓展现代物流的必要性、战略目标、创新策略及拓展对策.     

生态文明维度的海洋运输与海洋环境保护

生态文明的提出是对可持续发展理论认识深化的必然结果。当前以此为基点促进我国航运事业大发展必须关注海洋运输对海洋环境的负面影响;提出以生态文明建设为目标强化海洋环境保护的对策;坚持海洋运输低碳、环保的道德实践活动,保护海洋环境,维护海洋生态系统的平衡。     

基于集散效用和运输一体化枢纽布局优化模型

分析了综合运输枢纽规划与综合运网规划相互反馈的互动机制,提出以城市集散节点为主导的综合运输枢纽布局优化思路,并以综合运输集散、衔接综合广义费用最小为目标,建立了枢纽布局选址优化的混合整数规划模型;通过模型求解,从大型综合枢纽建设与综合运输体系构建的关系出发,引入了提高枢纽衔接效率和实现运输一体化的分析思路。分析认为：提出的综合运输枢纽布局优化模型构建、求解简单清晰,容易得到全局最优解,且能够反映枢纽和对外运网适应性密切的互动机制。