A utility-based travel impedance measure for public transit network accessibility

A utility-based travel impedance measure is developed for public transit modes that is capable of capturing the passengers’ behaviour and their subjective perceptions of impedance when travelling in the transit networks. The proposed measure is time-dependent and it estimates the realisation of the travel impedance by the community of passengers for travelling between an origin–destination (OD) pair.The main advantage of the developed measure, as compared to the existing transit impedance measures, relates to its capability in capturing the diversity benefit that the transit systems may offer the society of travellers with different traveling preferences. To clarify the necessity of such capability, we demonstrate the randomness (subjectivity) of travel impedance perceived by transit passengers, through evidence from the observed path choices made in the transit network of the greater Brisbane metropolitan region in Australia.The proposed impedance measure is basically a nested logit “logsum” composition over a generated set of reasonable path options whose systematic utilities are evaluated based on a discrete choice model previously developed and calibrated for the greater Brisbane transit passengers. As a case study, the proposed impedance measure is calculated for all the origin blocks in the Brisbane area, during the morning commutes to the Central Business District (CBD). The results are presented and discussed, and intuitive and important advantages are demonstrated for the proposed measure.     

城际长途慢行交通驿站间距设置研究

鉴于我国城际长途慢行交通设施建设快速发展,为提高其交通旅游服务水平,改善游客出行体验和控制建设成本,并为制订相关标准提供基础性指标,对慢行交通驿站设置间距进行了综合性量化研究。首先,构建了基于慢行交通人群出行过程的生理机能、不同情境下的应急需要及驿站设施建设成本等多因素的量化规划模型。然后,利用MATLAB软件求解函数极值,得到综合社会效益较优的驿站设置间距范围。最后,基于计算结果对《绿道规划设计导则》中驿站间距设置标准的合理性进行了验证,提出城际长途慢行交通服务驿站设施最佳间距为2.2～3.4km,并进一步推断出旅游公路服务驿站间距的设置原则。     

北京市小汽车通勤可达性变化及驱动因素分析

城市空间结构演化与交通发展之间存在动态互馈关系,可达性是连接二者的 关键纽带.基于潜能模型,在1 km × 1 km网格尺度上,计算了2000 年和2010 年北京市小 汽车的通勤可达性,并利用敏感性分析的思路研究通勤可达性变化的驱动因素.结果表 明,小汽车通勤可达性的时间变化体现为10 年间大幅提高,增长54%;空间上由中心区向 外围可达性递减的分布格局保持不变,但2010 年的可达性沿环路及高速公路蔓延的现 象更加明显,而且不同区域可达性变化的绝对值及变化率具有显著差异. 城市空间结构 变化对小汽车通勤可达性具有主要提升作用,但部分提升作用被路网运行速度的降低效 果所抵消.促进交通基础设施建设与城市空间布局的协调,仍是未来研究的重要课题.     

Examining the effect of speed,roadside features,and roadway geometry on crash experience along a rural corridor

This paper presents a current investigation into crash experience along a 15.7-mile rural corridor in southwest Montana with the aim of better understanding crash causal factors along the corridor. The study utilized ten years of crash data, geometric data, and observed freeflow speed data along the corridor. A systematic approach was used where every tenth of a mile was described in term of the crash experience, speed, alignment, and roadside features. Using bivariate and multivariate statistical anal-yses, the study investigated the crash experience along the corridor as well as some of the underlying relationships which could explain some of the crash causal factors. Results show a strong association between crash rates and horizontal curvatures even for flat curves that can be negotiated at speeds above the posted speed limit, per the highway design equations. Higher crash rates were also found to be associated with the difference between the observed free-flow speeds and the speed dictated by the curve radius or sight distance as per the design equations. Further, results strongly support the safety benefits of guardrails as evidenced by the lower crash rates and severities. The presence of fixed objects and the steepness of side slopes were also found to have an effect on crash rates and severities.     

基于公交时空过程的城市时空可达性计算方法

交通系统的本质目标是为了提高个体的可达性.已有的基于时空维的时空可达 性计算方法忽略交通模式选择的约束,以及对于出行时间没有确切的概念,因此,提出了 基于公交时空过程的城市时空可达性计算方法.该方法以特定的公交出行时空约束作为 效用函数,从历史公交时空过程中获取公交出行时间,对于出行时间的计算更具可操作 性;并且,其考虑特定的时空约束下个体参与活动的效用值,显得更加严谨.同时该方法将 特定的交通出行方式作为一种出行的时空约束,更加符合现实情况.最终,以广州市公交 系统为研究对象,运用该方法计算特定时空约束下个体出行的城市时空可达性.结果表明 该方法具有有效性和可操作性.     

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在城市轨道交通中,随着各条线路的末班车按运行计划逐站完成载客任务,路网上OD两点间的可达路径逐渐变少,直至两点间不可达,这样的路网服务能力随时间的动态变化,称为动态可达性。本文研究运行计划约束下的路网动态可达性计算方法,以支持末班车开行的优化,实现搭乘末班车出行乘客目的地可达的最大化。本文首先分析了末班车开行带来的动态可达性,给出了最晚可达时间、路径可达性、OD可达性定义。在此基础上,提出了末班车开行下路网可达性的计算方法与最晚可达时间求解的递归算法。最后,以路网可达性最大为目标,将可达性计算方法应用于末班车换乘衔接优化。通过算例分析验证了可达性计算方法的有效性。     

Effects of built environment on walking at the neighbourhood scale. A new role for street networks by modelling their configurational accessibility?

The hypothesis of this paper is that some features of the built environment, particularly those concerned with the accessibility of the street network, could be associated with the proportion of pedestrians on all trips (modal split) found in different parts of a city. Quantitative analysis (bi-variate correlation and a multiple regression model) was used to establish the association between variables. The study area covered a substantial part of the metropolitan area in Madrid, Spain. Results showed a consistent influence of five particular indexes in the multi-variate model. Not surprisingly for this kind of research, four of them described density and mix of land uses. But perhaps more interestingly, the first one was a measure of the accessibility of the public space network, a less prominent variable in literature to date. This variable is called herein configurational accessibility, calculated using Space Syntax, an urban morphology theory. The relevance of configurational accessibility is probably related to its surprising ability to synthesize global and perceived properties of street networks at the same time. The findings introduce the idea that the configuration of the urban grid can influence the proportion of pedestrians (as a part of total trips in any transport mode) who choose to walk on single-journey trips. The discussion links with the current debate about walkability indexes and the need of empirical support for the chosen variables and also with transport planning. Because the relevance of the street network’s role is not so easy to grasp, inputs from configurational theory and the pedestrian potential underlying this fact are also discussed at the end of the paper.     

基于绕行系数的交通可达性研究

为了评价不同路网形态下的城市道路可达性和对出行者的出行方式选择的影响,通过引入绕行系数的概念,对不同路网密度和交通管理策略的案例研究,说明可达性的变化对交通方式选择的影响。提出了基于绕行系数的可达性分析的基本思路,研究结果表明：仅以出行距离作为交通方式选择的影响要素条件下,可达性的改善有利于非机动出行方式分担率提高,合理的城市路网密度和适当的交通管理策略有利于多种交通方式共同发展。