The role of travel demand and network centrality on the connectivity and resilience of an urban street system

In the transportation literature, two major and parallel approaches exist to identify the critical elements of a transportation system. On the one hand, conventional transportation engineering emphasizes travel demand, often in terms of traffic volume (i.e., demand side). On the other hand, newer techniques from Network Science emphasize network topology (i.e., supply side). To better understand the relationship between the two approaches, we first investigate whether they correlate by comparing traffic volume and node centrality. Second, we assess the impact of the two approaches on the connectivity and resilience of a transportation network; connectivity is measured by the relative size of the giant component, and resilience is measured by the network’s adaptive capacity (the amount of extra flow it can handle). The urban road system of Isfahan (Iran) is used as a practical case study. Overall, we find that traffic volume indeed correlates with node centrality. In addition, we find that the weighted degree of a node, i.e., the sum of the capacities of its incident links (for small disruptions) and node betweenness (for large disruptions), best captures node criticality. Nodes with high weighted degree and betweenness should therefore be given higher priority to enhance connectivity and resilience in urban street systems. Regarding link criticality, roads with higher capacities showed a more important role as opposed to betweenness, flow, and congestion.

     

Correction to: The role of travel demand and network centrality on the connectivity and resilience of an urban street system

Transportation - In the original publication of the article, the first, second and fourth authors’ affiliations are published incorrectly.     

船舶压载水防治措施探讨

船舶压载水是外来海洋生物入侵的重要途径,严重危害水域生态平衡,破坏生物多样性,危害环境,造成严重的经济损失。本文针对压载水污染问题,从压载水的管理、处理技术、无压载舱船舶设计等方面,探讨压载水的预防途径和防治方法。     

Simulating the air quality impacts of traffic calming schemes in a dense urban neighborhood

In this study, the effects of isolated traffic calming measures and area-wide calming schemes on air quality in a dense neighborhood were estimated using a combination of microscopic traffic simulation, emission, and dispersion modeling. Results indicated that traffic calming measures did not have as large an effect on nitrogen dioxide (NO₂) concentrations as the effect observed on nitrogen oxide (NO_x) emissions. Changes in emissions resulted in highly disproportional changes in pollutant levels due to daily meteorological conditions, road geometry and orientation with respect to the wind. Average NO₂ levels increased between 0.1% and 10% with respect to the base-case while changes in NO_x emissions varied between 5% and 160%. Moreover, higher wind speeds decreased NO₂ concentrations on both sides of the roadway. Among the traffic calming measures, speed bumps produced the highest increases in NO₂ levels.     

Disentangling the influence of neighborhood type and self-selection on driving behavior: an application of sample selection model

The causality issue has become one of the key questions in the debate over the relationships between the built environment and travel behavior. Although previous studies have tested statistical and/or practical significance of the built environment on travel behavior, few have quantified the relative roles of the built environment and residential self-selection in influencing travel behavior. Using 1,479 residents living in four traditional and four suburban neighborhoods in Northern California, this study explores the causal effect of neighborhood type on driving behavior and its relative contribution to the total influence of neighborhood type. Specifically, this study applied Heckman’s sample selection model to separate the effect of the built environment itself and the effect of self-selection. The results showed that, on average, the effect of neighborhood type itself on driving distance was 25.8 miles per week, which accounted for more than three quarters of the total influence of neighborhood type and 16% of individuals’ overall vehicle miles driven. These results suggest that the effect of the built environment on driving behavior outweighs that of self-selection. This paper also discussed the advantages and weaknesses of applying the Heckman’s model to address the self-selection issue.

Exploring the link between the neighborhood typologies,bicycle infrastructure and commuting cycling over time and the potential impact on commuter GHG emissions

This paper investigates the evolution of urban cycling in Montreal, Canada and its link to both built environment indicators and bicycle infrastructure accessibility. The effect of new cycling infrastructure on transport-related greenhouse gas (GHG) emissions is then explored. More specifically, we aim at investigating how commuting cycling modal share has evolved across neighborhood built-environment typologies and over time in Montreal, Canada. For this purpose, automobile and bicycle trip information from origin–destination surveys for the years 1998, 2003 and 2008 are used. Neighborhood typologies are generated from different built environment indicators (population and employment density, land use diversity, etc.). Furthermore, to represent the commuter mode choice (bicycle vs automobile), a standard binary logit and simultaneous equation modeling approach are adopted to represent the mode choice and the household location. Among other things, we observe an important increase in the likelihood to cycle across built environment types and over time in the study region. In particular, urban and urban-suburb neighborhoods have experienced an important growth over the 10 years, going from a modal split of 2.8–5.3% and 1.4–3.0%, respectively. After controlling for other factors, the model regression analysis also confirms the important increase across years as well as the significant differences of bicycle ridership across neighborhoods. A statistically significant association is also found between the index of bicycle infrastructure accessibility and bike mode choice – an increase of 10% in the accessibility index results in a 3.7% increase in the ridership. Based on the estimated models and in combination with a GHG inventory at the trip level, the potential impact of planned cycling infrastructure is explored using a basic scenario. A reduction of close to 2% in GHG emissions is observed for an increase of 7% in the length of the bicycle network. Results show the important benefits of bicycle infrastructure to reduce commuting automobile usage and GHG emissions.     

Meta-analysis of the relationships between space syntax measures and pedestrian movement

ABSTRACT

Ample research has been conducted investigating the built environment impacts on pedestrian movement (PM). A clear division is also evident in the literature on this topic: one group tends to use geographic measures (metric distance) of the environment to explain pedestrian behaviour; the other group uses syntactic measures (visual distance). Many review articles have been published on the former. However, relatively little is known about the effect size (ES), directions, and consistency of syntactic measures in explaining PM. This paper fills this gap through a meta-analysis of published and unpublished studies on this topic spanning over 1975–2016, and answers the following five research questions: (a) What are the different measures used in the space syntax literature to explain PM?; (b) What are the magnitudes and directions of associations between space syntax measures and PM?; (c) Which space syntax measure has a more consistent relationship with PM?; (d) To what extent do the explanatory powers of different measures vary between their derivation methods?; and (e) What are the likely causes of variations of the reported results in prior studies? This research examined four syntactic measures (integration, connectivity, choice, and control) in a random effect model with 95% confidence interval (CI). The choice and integration measures were further investigated based on their operational approaches (topological, angular and metric). Results show that integration (ES?=?0.206, 95% CI?=?0.173–0.238, p?<?0.001), choice (ES?=?0.481, 95% CI?=?0.391–0.561, p?<?0.001), and connectivity (ES?=?0.305, 95% CI?=??0.225–0.696, p?=?0.257) measures positively influence PM with choice being the strongest predictor. Both connectivity and control (ES?=??0.001, 95% CI?=??0.117–0.115, p?=?0.990) were found to have a statistically insignificant impact. The choice and integration measures show stronger effects when derived using the angular approach (ES?=?0.493 for choice, and ES?=?0.502 for integration) compared to topological approach (ES?=?0.374 for choice, and ES?=?0.124 for integration). However, the reported results of all measures are highly heterogeneous, perhaps due to the differences in research design. The significance, magnitude, and consistency of integration and choice measures justify their relevance in built environment interventions to promote PM.     

Effects of neighborhood environments on perceived risk of self-driving: evidence from the 2015 and 2017 Puget Sound Travel Surveys

Autonomous vehicles (AVs), with an expectation of improving road safety, are closer to becoming a reality. A large number of people are still concerned about how AVs would operate in real-life driving environments. The present paper investigates the factors that affect people’s views of the interactions between AVs and other road users based on a large sample from the 2015 and 2017 Puget Sound Travel Surveys. We specifically highlight the effects of the neighborhood environment and road infrastructure. We estimate a generalized ordered logit model to demonstrate the extent to which certain neighborhood environment and road infrastructure features affect individuals’ safety perceptions of AVs, controlling for demographics, daily travel patterns, and general interest in riding AVs. The results reveal that designated bicycle facilities are positively associated with individuals’ safety perceptions related to AVs. We find that residents from neighborhoods with more pedestrian facilities are more likely to express higher levels of concern on AVs’ capabilities to react to the environment. Our results also suggest that people living in mixed-use neighborhoods are more confident in sharing the road with AVs. The findings provide useful implications for effective policy interventions and infrastructure provisions that may affect the market penetration rates of AVs while keeping up the standards for other road users, such as bicyclists and pedestrians.

     

Towards measures of affective and eudaimonic subjective well-being in the travel domain

Studies of the connections between transportation and subjective well-being (SWB) require a clear understanding of the conceptual composition of travel-related SWB as well as psychometric instruments to measure these complex topics. Well-established psychological scales for measuring general SWB—including both hedonic (affective and cognitive) and eudaimonic aspects—are difficult to adapt or have yet to be tested in the travel domain. Existing measures of travel liking and travel satisfaction are somewhat inadequate for these purposes, especially for representing eudaimonia. Using a questionnaire survey of 680 commuters in the Portland, Oregon, region, exploratory and confirmatory factor analyses examined responses to a total of 42 items. Results suggested four-factor measurement models of both travel affect (Enjoyment, Attentiveness, Distress, and Fear) and travel eudaimonia (Health, Competence, Autonomy, and Security). Despite some limitations and opportunities for enhancements, these models show promise as ways of measuring affective and eudaimonic SWB in the travel domain for future studies and travel surveys.

     

地铁车站边墙的变形特征及其控制措施

以上海市延长路地铁车站为背景,选取三个典型的地下连续墙水平位移监测点,根据其施工不同阶段的变形趋势,分析边墙的变形特征及其对环境的影响,并据此提出控制变形的有效措施.     

提高城市道路通行效率的几项措施

随着我国汽车保有量的增加,交通拥堵已成为城市的突出问题。城市交通的改善,应该从软硬件两方面着手,硬件主要在于道路规划与建设,软件主要在于优化交通管理措施。从目前的情况分析,软件手段对改善交通状况的潜力没有得到充分的发掘。应该从交通标线的设置、信号灯时间的设置、人行道规划、公交站点的规划、公路的拓扑结构等方面进行改进,提高城市道路的通行效率。     

Co-design of traffic network topology and control measures

The two main directions to improve traffic flows in networks involve changing the network topology and introducing new traffic control measures. In this paper, we consider a co-design approach to apply these two methods jointly to improve the interaction between different methods and to get a better overall performance. We aim at finding the optimal network topology and the optimal parameters of traffic control laws at the same time by solving a co-optimization problem. However, such an optimization problem is usually highly non-linear and non-convex, and it possibly involves a mixed-integer form. Therefore, we discuss four different solution frameworks that can be used for solving the co-optimization problem, according to different requirements on the computational complexity and speed. A simulation-based study is implemented on the Singapore freeway network to illustrate the co-design approach and to compare the four different solution frameworks.     

乌池坝特长公路隧道消防与防灾救援设计

即将开工建设的乌池坝特长公路隧道位于沪蓉国道主干线湖北恩施至利川的公路上,长约2×6.7 km,考虑到隧道所处的是一个特殊的环境,它受空间的限制,在发生火灾事故时,很有可能扩大到后续车辆,酿成更大的灾害,特别是特长公路隧道发生紧急事故时,救援困难,更容易造成严重损失,消防与防灾救援就显得十分重要.文章通过介绍该隧道的消防与防灾救援设计原则,以及采取的具体措施,提出了目前消防与防灾救援设计存在的问题和今后的研究方向.     

高性能海工混凝土灌注桩施工问题及方案改进措施研究

对灌注桩混凝土配合比质量和施工工艺进行了试验研究,对施工中存在的问题进行了分析,提出了改进方案。实践证明经济和社会效益显著。     

青藏铁路关角隧道病害的综合整治

文章详细地介绍了青藏铁路关角隧道的病害情况,并根据病害产生的原因采取了合理的整治措施.效果明显.为高原高寒隧道施工提供了可借鉴性的经验.     

西山坪隧道隧底煤层采空区的整治

西山坪隧道位于国道212线重庆至合川高速公路上,为双洞单向交通隧道,其中左洞长2 510 m,右洞长2 485 m;隧道穿越三叠系上统须家河组第三段时遇煤层采空区,需要进行整治后方能够保证隧道的安全。文章着重分析了采空区对隧道的不利影响及其处理方式。     

索道安全应急处理措施及救护预案

本阐明了在新的安全形势下索道安全应急处理在索道安全管理中的重要性,分析了可能导致索道临时停机的许多原因,并提出了相应安全应急处理措施,对于提高索道安全管理水平和优质服务质量具有重要意义。     

大跨黄土隧道设计与安全施工对策

作者根据多年的工程经验,对以往各线黄土隧道设计、施工和塌方情况进行总结和分析,结合郑西客运专线大断面黄土隧道的设计、施工情况,提出了大断面黄土隧道安全施工的对策,希望对拟建的包西、太中银等黄土隧道较多的铁路线有一定的参考价值.     

Performance measures and data requirements for congestion management systems

Many metropolitan areas have started programs to monitor the performance of their transportation network and to develop systems to measure and manage congestion. This paper presents a review of issues, procedures, and examples of application of geographic information system (GIS) technology to the development of congestion management systems (CMSs). The paper examines transportation network performance measures and discusses the benefit of using travel time as a robust, easy to understand performance measure. The paper addresses data needs and examines the use of global positioning system (GPS) technology for the collection of travel time and speed data. The paper also describes GIS platforms and sample user interfaces to process the data collected in the field, data attribute requirements and database schemas, and examples of application of GIS technology for the production of maps and tabular reports.     

高速公路车辆偷逃通行费的原因及应对措施

文章结合柳州高速公路运营有限公司收费管理实际,阐述了高速公路车辆偷逃通行费的基本情况,并多角度分析了车辆偷逃通行费的原因,提出了完善管理、强化堵漏、技术革新、法律支持的打击高速公路车辆偷逃通行费行为的措施与办法。