山岭重丘区公路选线探讨

山岭重丘区选线受地形、水文地质、路线交叉、公铁交叉等多种因素制约,线位的优劣是制约经济、合理、可行的重要因素。背景为山西省晋城市G207线过境段公路改线工程,结合项目选线过程中遇到的实际问题,提出本次选线的几点原则,通过不同线位的比较,最终确定较为合理、经济的线位,对类似工程项目具有一定的指导意义。     

高速公路互通式立交设计探析

互通式立交是高速公路网系统中重要的节点,它是保证交通流安全、有序的转换的重要设施。对互通式立交形式的选择,枢纽互通式立交合并出口及平交口的处理进行探讨,可为高速公路立交设计提供参考。     

现场总线式调速控制系统的结构及原理

介绍现场总线式调速控制系统的结构及原理，分析了该系统的技术特点及性能指标。     

高速公路扩建工程材料再利用施工技术及效益分析

为节省高速公路扩建工程中施工材料,可以对原本旧路面破除的材料进行循环利用.唐山至天津高速公路扩建工程破除材料全部利用再生技术,取得了良好的经济、社会效益,值得在同行中推广.     

永吉高速公路桥梁设计探讨

结合永吉高速公路桥梁特点,详细介绍山区高速公路桥梁的结构设计,上、下部构造宜采用的型式以及桥梁设计的一般原则,可为相关项目设计提供参考.     

论高速公路工程项目管理中的合同管理

近年来,随着经济的发展,我国高速公路的建设范围逐步扩大,与此同时,在建设施工过程中也暴露出很多问题.对高速公路建设过程中存在的漏洞和工程合同管理问题进行相应的分析,并站在施工单位的角度对不同项目的管理开发提出意见和建议,可供同行参考.     

高速公路养护维修方法探讨

随着汽车拥有量的不断增加,人们对出行安全非常关注,而其中高速公路的安全问题更是受到广泛关注。针对高速公路养护和维修的问题进行分析,探讨路基和路面养护和维修的具体措施与方法,可为高速公路养护工作提供参考。     

The Downs–Thomson Paradox with responsive transit service

Downs (1962) and Thomson (1977) suggested that highway capacity expansion may produce counterproductive effects on the two-mode (auto and transit) transport system (Downs–Thomson Paradox). This paper investigates the occurrence of this paradox when transit authority can have different economic objectives (profit-maximizing or breakeven) and operating schemes (frequency, fare, or both frequency and fare). For various combinations of economic objectives and operating schemes, the interaction between highway expansion and transit service is explored, as well as its impact on travelers’ mode choices and travel utilities. Further, for each combination, the conditions for occurrence of the Downs–Thomson Paradox are established. We show that the paradox never occurs when transit authority is profit-maximizing, but it is inevitable when the transit authority is running to maximize travelers’ utility while maintaining breakeven. This is because the former transit authority tends to enhance transit service (e.g., raise frequency or reduce fare) when facing an expanded highway; and on the contrary, the latter tends to compromise transit service (e.g., reduce frequency or raise fare). Both analytical and numerical examples are provided to verify the theoretical results.     

城市交通能耗区的识别及等级划分方法研究

随着社会经济的发展，机动车保有量急剧增长，城市化过程中交通拥堵问题日趋严重，交通能源消耗加剧。为了降低由此带来的损失，需要及时探明路网中交通效率低、能耗高的区域，并采取有效的交通管理措施。通过研究交通状态与能耗的关系，进行相应的交通参数分析，建立能耗区识别及等级划分模型，计算得到3个等级能耗区的界定阈值分别为0．411和0．678。     

Marine Protected Area Costs as “Beneficial” Fisheries Subsidies: A Global Evaluation

Marine protected areas (MPAs) are now generally accepted as important tools in the protection of coastal biodiversity. It is also likely that they play a positive role in enhancing fisheries. Yet currently, less than 1% of the global oceans are protected, although international agreements have targets ranging from 10–30% coverage. Despite its minuscule size, we consider the current MPA “network” to be beneficial to fisheries, and its running or maintenance cost, therefore, to be a positive contribution to the sustainability of fisheries, or a “beneficial” subsidy (“harmful” subsidies enhance fishing capacity and effort). A method was derived from data in Balmford et al. (PNAS, 101: 9694–9697) to estimate the annual cost of maintaining MPAs as a function of their size, and of the degree of development of the country in question. We provide national costs of the 53 countries that jointly contribute 95% of global fisheries catch and, assuming that this type of subsidy, in a given country, cannot exceed 15% of the ex-vessel value of its fisheries catches, estimated a global MPA subsidy to fisheries of 870 million US$. Given that total subsidies to fisheries currently range from 30–34 billion US$ annually (without MPA costs), this amounts to only 2.5–2.8% of total subsidies to fisheries being devoted explicitly to the maintenance of the biodiversity that sustains them.