探究公路勘察设计与环境保护的关联

文章首先分析了公路建设过程中对环境造成的影响,而后阐述了公路工程在路线设计时应注意的环境问题,最后列举了提升公路设计线路与环境环保的举措,希望降低工程在建设过程中对环保造成的不利影响。     

公路工程施工期生态环境保护初探

公路工程施工期可为公路沿线的生态环境带来巨大压力,本文结合实测数据分析了公路工程施工期对生态环境、声环境、大气环境、水环境、废弃物及光环境的影响,并以此为基础初步建立施工期的环境保护方案,以期为公路绿色施工环保方案编制提供参考。     

公路施工对环境的影响问题探讨

公路建设对经济和社会的发展有着不可替代的重要作用,但是公路施工也会给周边环境带来许多负面影响。文章就公路工程施工对环境的影响问题进行了研究,并探讨了优化环保监理的相关措施,以期为公路建设中的环境保护工作提供参考。     

公路工程施工对环境的影响及环保措施

在公路施工中对环境所产生的各种不良影响也逐渐的被人们重视,虽然公路工程施工对环境的破坏很难完全避免,但是我们可以通过有效的环保措施尽量减少公路工程对周围环境造成的污染和破坏.     

公路工程沉降段路基路面设计要点研究

现阶段公路工程仍然存在着道路沉降的问题,导致公路路面不平,行车过程中存在一定的不安全性且行车舒适体验感较差。对此,相关部门需要加强对公路工程沉降段路基路面的设计,以保证公路工程的建设质量满足人们的实际需求。通过对公路工程沉降段路基路面的设计要点进行了分析,首先结合实际分析常见的公路工程沉降段位置,然后指出公路工程路基路面沉降段设计应考虑的因素,最后提出沉降段路基路面设计处理措施。     

浅析公路工程施工中的环保问题

分析了公路工程开工前期、施工期等各个阶段对沿线自然环境造成的影响,有针对性地提出相应的环保措施,以减少公路工程给自然环境带来的不利影响.     

公路工程水泥稳定碎石基层裂缝问题成因及防治措施研究

为提高公路工程水泥稳定碎石基层质量,有效避免裂缝问题,结合多个项目实践经验,对基层裂缝成因进行研究。在此基础上提出相应的防治措施,具体包括控制路基不均匀沉降、原材料质量控制、水泥稳定碎石基层混合料配合比设计优化等,以期为相关工程提供参考,进一步提高公路工程使用寿命。     

高速公路工程节能与环保施工对策浅议

由于公路工程的特殊性,在施工过程中必然会产生较大的噪音,同时还会对整个生态环境造成一定的影响,随着人们环保意识的提高,公路建设过程中的环保问题逐渐引起社会公众的注意.基于此,本文针对公路工程施工过程中,如何有效避免对环境的污染进行了深入的探讨,同时针对具体问题提供解决办法,以供参考.     

公路路基及基层设计参数的研究

公路路基设计参数决定着公路工程的质量。本文主要对河南省公路工程建设中的相关设计参数进行了研究。     

公路工程施工中混凝土裂缝成因与施工策略分析

为有效解决公路工程施工中混凝土裂缝问题,保证工程施工质量,消除安全隐患,从公路工程施工中混凝土裂缝的危害入手,阐释混凝土裂缝成因。在此基础上,提出解决公路工程施工中混凝土裂缝问题的措施,包括优化工程建设前期的勘测与设计、严格控制施工材料质量、严格管控施工温度等,希望可以为相关领域工作人员提供借鉴。     

Survey of R&D in PRT systems

A survey of research and development in advanced transit has been made by Chalmers University of Technology in Gothenburg in cooperation with Trans21 in Boston. Summary findings are reported for fourteen academic research programs and ten development programs for PRT. An earlier version of this paper was presented at the International Conference of PRT and other Emerging Systems held in Minneapolis in 1996.     

管道风险分析指数评分法中分值调整初探

管道风险分析指数评分法中重要步骤之一就是确定影响管道事故因素的权重,各个管道风险因素在整个管道事故中所占的权重是不相同的。针对目前管道风险分析指数评分法基本假设之一（各因素的分值范围都是0～100分）,为了更加客观、准确、合理地反映各个风险因素对于管道事故的影响程度,提出并论述了依据层次分析法的数学逻辑性进行综合计算得出管道风险因素的权重,然后对评分法中各个因素的最高分值,根据其权重不同进行相应调整,从而增强评价者对风险因素的认识和评判能力,提高管道风险评价结果的准确性。     

Determinants of modal choice in freight transport

In the next few years, exciting developments in the field of freight transport are likely to occur. The Channel Tunnel will be perceived as giving railways much greater distance of operation, compared to the current train ferry to/from Great Britain. The further development of swap-body technology will allow easier modal transfer and the creation, in 1992, of a single market in Europe will transform the pattern of trade. All of these are likely to have significant impacts on modal choice, and hence modal split, in freight transport. Reappraisal by many firms of the modes of transport used is likely but will it result in a net transfer of freight from road to rail and, if so, to what extent? To answer such questions, an accurate and reliable method of predicting modal split is required. Research in the past has concentrated on the development of modal split models based on generalised costs. These fail to explain adequately the prevalence of road freight in the UK. From surveys of freight managers within industry, it is clear that models to date rely too heavily on the economic cost factor and too little on behavioural factors (Jeffs 1985). This paper derives from a recent study of freight transport modal choice from the standpoint of the transport decision-maker within the firm. It attempts to shed light on the actual parameters which should be incorporated into a modal split model. Many variables appear to exert an influence on modal choice decision-making process. However, it is possible to categorise them into six main groups, namely: customer-requirements; product-characteristics; company structure/organisation; government interventions; available transport facilities; and perceptions of the decision-maker him/herself. It is the interactions and inter-relationships between these which ultimately determine freight modal split. This study has shown that the relationship between the outcome of the transport decision process and the values of particular determinants of modal split is not straight-forward, due to the complexity and variety of interactions involved. Perhaps one of the main reasons for researchers' failure hitherto to develop a successful modal-split model has been the preoccupation with techniques that rely on the development of common metric (e.g. generalised cost), which has led to the exclusion of some important explanatory variables along quite different dimensions. Another important issue concerns the appropriate level of aggregation. In order not to reduce the explanatory power of the key variables, it is important to work at a disaggregate level, although this does make substantial demands on data. The use of factor analysis enables both the aggregation of information without loss of behavioural reality and the specification of variables in terms of a common metric. In conclusion, freight transport has usually been examined within too narrow a framework. It must be placed firmly within the context of the total industrial process. The demand for freight transport is directly influenced by the level, composition and geographical distribution of production and consumption activities. Freight flows are complex and so it is highly unlikely that a universal mode-choice model can ever be developed. Future research should, therefore, be directed towards developing partial models in response to specific needs of those involved in decision-taking in the freight sector.     

A century of evolution of the accessibility concept

The concept of accessibility has acquired numerous meanings along multiple dimensions during the century of its evolution. This essay argues for the salience of two dimensions: application-based and definition-based. In its application, accessibility has incorporated positive and normative dimensions which have varied in prominence over time. In its definition, accessibility has varied between a mode of evaluation incorporating measured mobility and proximity, on the one hand, and a predefined market basket of urbanist improvements to transportation and land use systems, on the other. Advocates of the accessibility shift should emphasize both the measured approach to accessibility and accessibility’s normative side.     

Optimization of bus stop locations for improving transit accessibility

A mathematical model is developed in this paper to improve the accessibility of a bus service. To formulate the optimization model, a segment of a bus route is given, on which a number of demand entry points are distributed realistically. The objective total cost function (i.e. the sum of supplier and user costs) is minimized by optimizing the number and locations of stops, subject to non‐additive users' value of time. A numerical example is designed to demonstrate the effectiveness of the method thus developed to optimize the bus stop location problem. The sensitivity of the total cost to various parameters (e.g. value of users' time, access speed, and demand density) and the effect of the parameters on the optimal stop locations are analyzed and discussed.     

Productive efficiency and ownership of urban bus services

The established ownership mix of urban bus operations in Australia provides a unique opportunity to investigate the productivity differences between public and private bus service supply. Using duality theory in economics which links economic indices of factor productivity to the cost structure of a firm, we develop empirical measures of total and partial productivity of inputs, and adjust the differences for the effects of ownership status and operating environment. The evidence supports the notion that private supply of public passenger transport in general has performed more efficiently in the past than public supply, although the differences in productivity need not continue in the future.     

Governing autonomous vehicles: emerging responses for safety,liability, privacy,cybersecurity, and industry risks

ABSTRACT

The benefits of autonomous vehicles (AVs) are widely acknowledged, but there are concerns about the extent of these benefits and AV risks and unintended consequences. In this article, we first examine AVs and different categories of the technological risks associated with them. We then explore strategies that can be adopted to address these risks, and explore emerging responses by governments for addressing AV risks. Our analyses reveal that, thus far, governments have in most instances avoided stringent measures in order to promote AV developments and the majority of responses are non-binding and focus on creating councils or working groups to better explore AV implications. The US has been active in introducing legislations to address issues related to privacy and cybersecurity. The UK and Germany, in particular, have enacted laws to address liability issues; other countries mostly acknowledge these issues, but have yet to implement specific strategies. To address privacy and cybersecurity risks strategies ranging from introduction or amendment of non-AV specific legislation to creating working groups have been adopted. Much less attention has been paid to issues such as environmental and employment risks, although a few governments have begun programmes to retrain workers who might be negatively affected.     

Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO_x) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO_x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO_x emitter.