Transport network criticality metrics: a comparative analysis and a guideline for selection

ABSTRACT

Transport network criticality analysis aims at ranking transport infrastructure elements based on their contribution to the performance of the overall infrastructure network. Despite the wide variety of transport network criticality metrics, little guidance is available on selecting metrics that are fit for the specific purpose of a study. To address this gap, this study reviews, evaluates and compares seventeen criticality metrics. First, we conceptually evaluate these metrics in terms of the functionality of the transport system that the metrics try to represent (either maintaining connectivity, reducing travel cost, or improving accessibility), the underlying ethical principles (either utilitarianism or egalitarianism), and the spatial aggregation considered by the metrics (either network-wide or localised). Next, we empirically compare the metrics by calculating them for eight transport networks. We define the empirical similarity between two metrics as the degree to which they yield similar rankings of infrastructure elements. Pairs of metrics that have high empirical similarity highlight the same set of transport infrastructure elements as critical. We find that empirical similarity is partly dependent on the network’s topology. We also observe that metrics that are conceptually similar do not necessarily have high empirical similarity. Based on the insights from the conceptual and empirical comparison, we propose a five-step guideline for transport authorities and analysts to identify the set of criticality metrics to use which best aligns with the nature of their policy questions.     

500米长轨营业线火车市场运费与概预算编制办法计算运费对比分析

随着《铁路基本建设项目投资管理办法》(铁总计统〔2017〕179号)及《关于铁路建设项目清理概算工作的通知》(发改投资电〔2019〕1号)文的出台,标志着铁路建设项目概算清理工作,将逐步交由建设单位按照不突破初步设计批复金额进行处理,因此初步设计阶段如何确保招标预算金额的准确性,体现的越来越为重要,本文通过对500米长轨营业线火车市场运费与编制办法计算运费的分析,量化两者费用存在的差异,列明差异原因,并提出相关建议。     

香港“城铁一体化”开发模式对城际轨道交通可持续发展的启示

当前国内城际轨道交通的发展对以轨道交通为导向的城市综合开发提出更高的要求,针对性剖析香港铁路发展历程和成功经验,结合相关数据分析,研究"城铁一体化"综合开发模式对城际轨道交通可持续发展的作用和意义,对该模式下的财务、政策和技术层面的问题进行探讨,提出"城铁一体化"开发须在政策层面制定相应的"权益流程",实施开发建设的集约化;在运营层面体现"共赢"原则,构建"轨道交通运营+效益返还"机制;针对城市各区域发展不同步的特点,在一体化建设中采用灵活的预留机制满足分期建设的需求,最终实现轨道交通的可持续发展。     

某磁浮大跨斜拉桥竖向刚度限值研究

以某磁浮轨道交通(40+80+228+228+80+40)m大跨钢箱梁斜拉桥为研究对象,采用有限元软件ANSYS和多体动力学软件UM分别建立桥梁和磁浮列车模型。基于车桥耦合振动方法,针对2列磁浮列车相向行驶并在主跨跨中交会的最不利情形,进行列车以不同速度通过桥梁时不同梁高下车桥系统的动力响应及磁浮大跨桥梁的竖向刚度限值研究。结果表明:磁浮列车的竖向动力响应随车速的增大而显著增大,时速从40 km增大到140 km时,列车竖向动力响应增幅达到120%以上;车体竖向加速度和Sperling指标不是桥梁结构刚度限值的控制因素;磁浮列车的悬浮间隙对梁体刚度变化较为敏感,随着梁体刚度逐步增大,悬浮间隙的波动变小,梁体挠跨比减小约25%,悬浮间隙波动减小幅度达35%,悬浮间隙可作为中低速磁浮大跨桥梁结构刚度限值的控制指标;梁体挠跨比1/3015可作为磁浮大跨桥梁的竖向刚度限值。     

旅游交通规划成套技术探究

从行业、角度、目标和路径四大方面更新旅游交通规划理念,建立时空、资源、体验三大模块规划体系,达到旅游交通网络构建、功能拓展、配套完善的效果。在此规划体系基础上,根据不同地区特色,突出主题品牌设计,创新产品供给,紧密结合当地规划与落地方案,形成了丰富的规划应用成果,为交旅融合快速发展奠定理论基础。     

Assessment of antenna characteristic effects on pedestrian and cyclists travel-time estimation based on Bluetooth and WiFi MAC addresses

Monitoring pedestrian and cyclists movement is an important area of research in transport, crowd safety, urban design and human behaviour assessment areas. Media Access Control (MAC) address data has been recently used as potential information for extracting features from people’s movement. MAC addresses are unique identifiers of WiFi and Bluetooth wireless technologies in smart electronics devices such as mobile phones, laptops and tablets. The unique number of each WiFi and Bluetooth MAC address can be captured and stored by MAC address scanners. MAC addresses data in fact allows for unannounced, non-participatory, and tracking of people. The use of MAC data for tracking people has been focused recently for applying in mass events, shopping centres, airports, train stations, etc. In terms of travel time estimation, setting up a scanner with a big value of antenna’s gain is usually recommended for highways and main roads to track vehicle’s movements, whereas big gains can have some drawbacks in case of pedestrian and cyclists. Pedestrian and cyclists mainly move in built distinctions and city pathways where there is significant noises from other fixed WiFi and Bluetooth. Big antenna’s gains will cover wide areas that results in scanning more samples from pedestrians and cyclists’ MAC device. However, anomalies (such fixed devices) may be captured that increase the complexity and processing time of data analysis. On the other hand, small gain antennas will have lesser anomalies in the data but at the cost of lower overall sample size of pedestrian and cyclist’s data. This paper studies the effect of antenna characteristics on MAC address data in terms of travel-time estimation for pedestrians and cyclists. The results of the empirical case study compare the effects of small and big antenna gains in order to suggest optimal set up for increasing the accuracy of pedestrians and cyclists’ travel-time estimation.     

基于GT-Power和Simulink的柴油机各缸不均匀性闭环控制

为改善各缸工作不均匀性,以TBD314V8柴油机为研究对象,基于缸压计算得到的各缸IMEP和CA50作为反馈变量,控制变量为各缸的喷油量和喷油提前角,建立了GT-Power与Simulink联合仿真模型,通过模型分析了轨压、负荷和喷油提前角对爆压、IMEP和CA50不均匀率的影响,并对影响因素进行参数灵敏度量化分析,验证了闭环控制对各缸不均匀性的改善效果。结果表明：轨压对爆压、IMEP和CA50不均匀率影响较小;负荷对IMEP不均匀率影响最大,且随着负荷的增加呈线性下降;喷油提前角对爆压不均匀率和CA50不均匀率影响最大,且CA50不均匀率随着喷油提前角的增大呈线性增加。经过闭环控制后,各缸不均匀性得到明显改善。     

Does transport help people to gain employment? A systematic review and meta-analysis of the empirical evidence

ABSTRACT

The role of transport in providing access to employment has received considerable attention. Since transport policies may be motivated by assumed effects on employment probability outcomes, it is important to establish the nature of the relationship between transport and employment outcomes. While the majority of the empirical evidence suggests a positive association, it is not conclusive or consistent and often shows mixed results. To address this confusion, our study has systematically reviewed this evidence base and synthesised it through meta-analysis. We first identified 93 studies that quantitatively assessed the impact of transport on employment outcomes. By systematically merging the empirical evidence, this study establishes a positive association between transport and employment outcomes, with varying effects for four identified categories of transport measures (or combinations thereof): car ownership, public transport access, commute times, and job accessibility levels. This positive association persists in studies that control for endogeneity between transport and employment, but a larger evidence base is needed to establish a more robust relationship, in particular for cities and smaller (rural) areas outside the US-context and with regard to public transport. We then selected 20 methodologically comparable studies for inclusion in the meta-analysis. Our meta-regression models clearly demonstrate that car ownership significantly increases individual employment probabilities, in particular among welfare recipients. Young drivers benefit from access to household cars when these are not in use by their parents, and they are more sensitive to the time and cost implications of longer commutes. While our systematic review suggests that better access to public transport and higher levels of job accessibility increases employment probabilities, meta-regression analysis requires more consistent transport measures. The findings in this study are important for policymakers in that they imply that job seekers may benefit from public policies targeted at improving their access to public transport, in particular for people without access to cars and in areas with fewer job opportunities.     

The desulphurisation of shipping: Past,present and the future under a global cap

As from January 2020, the International Maritime Organization (IMO) is implementing a global 0.5% limit on the sulphur content of fuel, commonly known as the global sulphur cap. This limit is the latest policy in the efforts to reduce sulphur emissions from shipping, following the designation of emission control areas (ECAs) and other regional regulations. In this paper, a literature review is conducted of academic studies that have dealt with issues relating to the reduction of maritime sulphur emissions. Various recurring research themes are identified, spanning the areas of operations research, maritime economics and transport policy. The effects and implications of available compliance options are then analyzed from the perspectives of ship operators, shippers and consumers. Using lessons learned from the enforcement of ECA regulations, this is followed by an appraisal of various potential issues related to the enforcement of these new global regulations. It is found that a homogeneous enforcement regime is required to ensure a level playing field amongst ship operators and that the global sulphur cap may lead to serious market distortion, due to the potential short term rise of fuel prices. The paper concludes with a set of recommendations for future research on sulphur emissions from shipping in the aftermath of the global cap and, looking forward, to its relationship to the IMO strategy on the reduction of greenhouse gas (GHG) shipping emissions.     

船台测量场中多级转站的不确定度

对在船台测量场内利用全站仪进行多级转站测量时误差的传递过程进行研究,分析误差的来源及其累积方法,建立转站过程中误差传递的数学模型,并据此推导出多级转站测量的系统误差传递公式及其不确定度估计公式。采用蒙特卡洛方法开展考虑全站仪测量误差的多级转站过程仿真试验,并将仿真结果与计算结果相对比。结果表明,提出的误差估计方法能较好地反映多级转站时误差的传递过程和不确定度的分布规律。