Measuring Accessibility for People with a Disability

This paper discusses some of the inherent problems associated with measuring accessibility for people on a landscape of surfaces, barriers, and travel modes. Along with this discussion we propose a new perspective for measuring accessibility with a focus on people with differing abilities. Even though our focus is on people with a physical disability, such an approach can be easily extended and is able to be generalized to other needs and differences. Traditional measurements of accessibility are flawed, as they fail to directly account for mobility and physical differences among people. They ignore structural barriers and individual mobility limitations that affect travel time, effort, and even successful completion. To make sense of this dilemma, we propose an accessibility measurement framework that includes measures of absolute access, gross access, closest assignment access, single and multiple activity access, probabilistic choice access, and relative access. Most of these measures of access have been proposed by others, but our framework attempts to codify an approach that helps to overcome weaknesses in using only the absolute access measurement currently used in ADA compliance. Such measures can be used to map accessibility as well as to help select the mitigation or renovation projects that yield the greatest increase in accessibility for people with disabilities. We argue that for many urban and building design problems providing absolute access for people with physical disabilities should be accompanied by the use of a relative access measurement, so that removing barriers can be done in the order that provides the greatest improvement in access for a given level of expenditure.     

Space-Time and Integral Measures of Individual Accessibility: A Comparative Analysis Using a Point-based Framework

Conventional integral measures of accessibility, although valuable as indicators of place accessibility, have several limitations when used to evaluate individual accessibility. Two alternatives for overcoming some of the difficulties involved are explored in this study. One is to adapt these measures for evaluating individual accessibility using a disaggregate, nonzonal approach. The other is to develop different types of measures based on an alternative conceptual framework. To pursue the former alternative, this study specifies and examines eighteen gravity-type and cumulative-opportunity accessibility measures using a point-based spatial framework. For the latter option, twelve space-time accessibility measures are developed based on the construct of a prism-constrained feasible opportunity set. This paper compares the relationships and spatial patterns of these thirty measures using network-based GIS procedures. Travel diary data collected in Columbus, Ohio, and a digital data set of 10,727 selected land parcels are used for all computation. Results of this study indicate that space-time and integral indices are distinctive types of accessibility measures which reflect different dimensions of the accessibility experience of individuals. Since space-time measures are more capable of capturing interpersonal differences, especially the effect of space-time constraints, they are more “gender sensitive” and helpful for unraveling gender/ethnic differences in accessibility. An important methodological implication is that whether accessibility is observed to be important or different between individuals depends heavily on whether the measure used is capable of revealing the kind of differences the analyst intends to observe.     

AN ECONOMIC INTERPRETATION OF KUHN'S DUAL FOR THE STEINER-WEBER PROBLEM A NOTE*

In this paper, we given an economic interpretation of Kuhn's dual of the Steiner-Weber problem. It depends essentially on the notion that different transportation systems arerelevant for the primal and the dual. Moreover, the Euclidean metric underlies the interpretation of the primal, the block one that of the dual.     

Exploring the associations between cooling centre accessibility and marginalization in Montreal,Toronto, and Vancouver,Canada

Cooling centres provide respite, safety, and social support during extreme heat events for populations that do not have the resources to own or operate in-home air conditioning. The objective of this study was to measure the spatial accessibility of cooling centres and analyze the associations between cooling centre access and marginalization in Montreal, Toronto, and Vancouver, Canada. The potential spatial accessibility of cooling centres within a 15-minute walk was measured at the dissemination area scale using the two-step floating catchment area method. A two-stage modelling approach was used to analyze the associations between cooling centre access and marginalization. Approximately 62%, 58%, and 54% of the populations in Montreal, Toronto, and Vancouver had access to at least one cooling centre. In Montreal and Vancouver, high marginalization areas were more likely to have cooling centre access than low marginalization areas. Of the areas with cooling centre access, smaller access scores were observed in areas with high residential instability. Approximately one-fifth of the areas in each city had no cooling centre access and high marginalization, and may be considered for future cooling centres or programs that improve accessibility to existing centres.     

珠江三角洲陆路运输网络效率测度及其演化

构建运输网络效率测度模型,对珠江三角洲27个县域单元1980年代以来运输网络效率的时空演化特征进行分析,结论表明:相较传统的通达性指标,网络效率指标在识别交通网络发展状况方面更有效;珠三角运输网络效率空间分异模式与通达性空间分异模式有较大差异,网络效率低值点和高值点同时存在于核心和外围地区;1988-2008年,随着珠三角陆路交通网络的发展,运输网络效率空间格局从原有的南北向"走廊"分布态势,转变为东西向面状均衡分布格局;运输网络效率水平大幅提升,网络效率平均值从4.42减少到1.41小时,变化率达到68.09%。各城市陆路运输网络效率与其城市发展关系表现为高度支撑型、基本支撑型、基本适应型及高度适应型四类。     

An Examination of the Stochastic Distribution of Spatial Accessibility to Intensive Care Unit Beds during the COVID-19 Pandemic: A Case Study of the Greater Houston Area of Texas

Sufficient and reliable health care access is necessary for people to be able to maintain good health. Hence, investigating the uncertainty embedded in the temporal changes of inputs would be beneficial for understanding their impact on spatial accessibility. However, previous studies are limited to implementing only the uncertainty of mobility, while health care resource availability is a significant concern during the coronavirus disease (COVID-19) pandemic. Our study examined the stochastic distribution of spatial accessibility under the uncertainties underlying the availability of intensive care unit (ICU) beds and ease of mobility in the Greater Houston area of Texas. Based on the randomized supply and mobility from their historical changes, we employed Monte Carlo simulation to measure ICU bed accessibility with an enhanced two-step floating catchment area (E2SFCA) method. We then conducted hierarchical clustering to classify regions of adequate (sufficient and reliable) accessibility and inadequate (insufficient and unreliable) accessibility. Lastly, we investigated the relationship between the accessibility measures and the case fatality ratio of COVID-19. As result, locations of sufficient access also had reliable accessibility; downtown and outer counties, respectively, had adequate and inadequate accessibility. We also raised the possibility that inadequate health care accessibility may cause higher COVID-19 fatality ratios.     

Measuring Regional Cohesion Effects of Large-scale Transport Infrastructure Investments: An Accessibility Approach

Transport infrastructure is considered one of the main policy instruments to achieve the cohesion goal, although the inclusion of cohesion effects in assessment methodologies is scarce and uneven. Although most cohesion studies are constrained to the analysis of regional disparities in economic indicators, this approach can be broadened to include other regional performance indicators. One of these indicators could be accessibility measures, from the point of view that accessibility, representing a competitive advantage of locations, constitutes a “desirable good” closely related to the welfare of each region. This paper suggests using changes in the spatial distribution of accessibility as a proxy to assess regional cohesion effects of transport infrastructure investments. However, as the conclusions taken depend heavily on the formulation of the accessibility measure, we recommend computing a set of accessibility indicators and analysing their results in a complementary way. The proposed methodology is tested by assessing regional cohesion effects of the large-scale road and rail transport infrastructure investments carried out in Spain in the period 1992–2004. The results obtained show that cohesion has improved for the road mode, while regional disparities have increased for the rail mode. This paper identifies the main factors driving this final cohesion effect and explores the strengths and weaknesses of the different accessibility indicators that were considered. The approach suggested in this paper has the potential to be applied in transport planning processes, and may eventually complement existing strategic assessment methodologies.     

IF ALONSO WAS RIGHT: MODELING ACCESSIBILITY AND EXPLAINING THE RESIDENTIAL LAND GRADIENT

ABSTRACT This study provides an empirical evaluation of employment accessibility as a determinant of urban land price. We find that the monocentric model, despite recent criticism, can perform satisfyingly if the hedonic value of land is identified in an account of structural and neighborhood characteristics. Gravity employment accessibility measures, however, can explain the residential land gradient entirely and disentangle positive accessibility effects from negative congestion effects related to transport infrastructure. They can therefore be recommended as an appropriate mean to account for labor market accessibility in an environment of dispersed employment, at least if the transport geography is accounted for.     

南京市社区服务设施可达性的空间格局与低收入社区空间剥夺研究

社区服务设施的空间可达性事关城市公共资源分配的社会公平与公正,是反映城市居民生活质量的重要标志。以南京市居住用地作为基本分析单元,对南京市的教育、医疗、商业和公园绿地四大类社区服务设施的空间可达性进行分析;并通过对相关低收入社区的实地调研,研究城市边缘区低收入群体的服务设施空间剥夺问题。研究表明：南京市四类服务设施的可达性水平均呈现出由城市中心区向郊区衰减的空间分异格局;较低的社区服务设施可达性不仅直接造成低收入社区居民对社区服务设施较低的满意度,导致其空间剥夺感的产生,还极大地阻碍着社区归属感的形成,导致社区居民强烈的迁居欲望,在他们较低的支付能力下进一步加剧其空间剥夺感。政府未来在规划面向低收入群体的保障性社区时,更应注重相关服务配套设施建设,做到社会与空间的公正性。     

Revisiting the structuring effect of transportation infrastructure: An empirical approach with the French railway network from 1860 to 1910

The development of the French railway network was mostly planned in a centralized manner. Despite the multiplication of travel opportunities, the local impact on the demographics is often given as an indirect effect of this spatial transformation. However, this “structuring effect” is still subject to controversies within the academia.

In this paper, we construct a historical geographic information system describing the evolution of the French network. We use it to compute accessibility measures based on network access and travel durations. We first observe that the network growth indeed achieved the various planning goals in terms of functional accessibility. We then present further evidences that the “structuring effect” of the train network on cities demographics is very limited if not null.     

移动搜索法在教育公共服务可达性评价中的改进与应用——以福州城区幼儿园为例

采用可变步长的两步移动搜索法,以福建省福州市为典型案例,以居民点（普查小区）为分析单元,对各居民点入园空间可达性进行了测算,并与传统的两步移动搜索法进行对比分析,综合判别学前教育资源空间分布特点。研究表明：福州城区入园可达性总体情况并不理想,仅有少数地区、少量人群可以获得较好的幼儿园空间的可达性。入园可达性在地理空间上呈现出多中心结构,高可达性地区主要分布在市中心并在城市周围零星分布,边缘乡镇特别是除西部以外的乡镇地区缺教明显,入园可达性在城区内部差异较大,幼儿园资源过剩地区和稀缺地区呈两极分化的格局。可变步长的两步移动搜索法能更为客观有效地对幼儿园的布局状况进行评价。而传统方法有一定的夸大作用,且降低了内部的差异,在一定程度上掩饰了幼儿园资源分布的不公平现象。     

A Measure of Competitive Access to Destinations for Comparing Across Multiple Study Regions

Accessibility is now a common way to measure the benefits provided by transportation–land use systems. Despite its widespread use, few measurement options allow for the comparison of accessibility across multiple urban systems, and most do not adequately control for market competition between demand-side actors and supply-side facilities in localized markets. In this article, we develop a measure of competitive access to destinations that can be used to accurately compare accessibility between regions. This measure stems from spatial interaction modeling and accounts for competition at both the supply and demand sides of analysis, regional differences in transportation networks and travel behavior, and any imbalance between the size of the population and the number of opportunities. We use this method to compute access to employment for Canada's eight largest cities to comparatively examine inequalities in accessibility, both within and between cities, and by travel mode.     

Strengths and weaknesses of accessibility instruments in planning practice: technological rules based on experiential workshops

Accessibility instruments can play a valuable role in urban planning practice by providing a practical framework for exploring and testing relationships between land use and transport infrastructure. Despite many available accessibility instruments, they are still not widely used in planning practice. This paper explores the background of this problem by examining the findings of a EU-funded study on the usability and usefulness of existing accessibility instruments. The study applied 16 instruments in local planning contexts according to a standardized process protocol. The outcomes of these so-called experiential workshops were analysed through a standardized measurement protocol, which included participant observation along with pre- and post-workshop practitioner questionnaires. This broad investigation presents a rich analytical tool for understanding how different types of accessibility measures, spatial resolutions of output and levels of comprehensiveness affect usability and usefulness. Based on this we propose 10 technological rules that (a) can be used directly in practice to improve usability of accessibility instruments and (b) can provide hypotheses to be examined in further academic studies. Our results suggest that instead of striving for the ultimate accessibility measure, it would be more effective to identify which measures could successfully serve different user needs in accessibility planning.     

Measuring Space-Time Accessibility Benefits within Transportation Networks: Basic Theory and Computational Procedures

Accessibility is a fundamental but often neglected concept in transportation analysis and planning. Three complementary views of accessibility have evolved in the literature. The first is the constraints-oriented approach, best implemented by Hägerstrand's space-time prisms. The second perspective follows a spatial interaction framework and derives “attraction-accessibility measures” that compare destinations' attractiveness with the travel costs required. A third approach measures the benefit provided to individuals by the transportation/land-use system. This paper reconciles the three complementary approaches by deriving space-time accessibility and benefit measures that are consistent with the rigorous Weibull axiomatic framework for accessibility measures. This research also develops computational procedures for calculating these measures within network structures. This provides realistic accessibility measures that reflect the locations, distances, and travel velocities allowed by an urban transportation network. Since their computational burdens are reasonable, they can be applied at the urban scale using a GIS.     

公共交通可达性分析方法进展

公共交通可达性拥有空间属性、时间属性、社会属性和经济属性,它是一种衡量区位价值的综合性指标,不仅可以反映城市空间特征,同时对城市中生活的人的社会经济属性和生活习惯,具有一定的解释力。为了不断适应新形势下的交通发展要求,减少环境负担,早日实现低碳绿色发展,创新公交都市规划与分析方法迫在眉睫。本文对基于个人的、基于效用的、基于基础设施的和基于位置的可达性研究进行了回顾,并归纳了七种公共交通可达性的分析方法,分别为：基于缓冲区的公共交通站点可达性、基于供需模型的公共交通面状可达性、基于网络分析法的公共交通网络可达性、基于成本栅格法的公共交通可达性、基于成本栅格与网络分析的集成法的公共交通可达性、基于高性能图形数据库的公共交通高精度可达性、基于开放地图 API 的公共交通高精度可达性。 以期为我国未来公共交通可达性的分析方法提供指引和借鉴。     

Measuring Space-Time Accessibility Benefits within Transportation Networks: Basic Theory and Computational Procedures

Accessibility is a fundamental but often neglected concept in transportation analysis and planning. Three complementary views of accessibility have evolved in the literature. The first is the constraints-oriented approach, best implemented by Hägerstrand's space-time prisms. The second perspective follows a spatial interaction framework and derives “attraction-accessibility measures” that compare destinations' attractiveness with the travel costs required. A third approach measures the benefit provided to individuals by the transportation/land-use system. This paper reconciles the three complementary approaches by deriving space-time accessibility and benefit measures that are consistent with the rigorous Weibull axiomatic framework for accessibility measures. This research also develops computational procedures for calculating these measures within network structures. This provides realistic accessibility measures that reflect the locations, distances, and travel velocities allowed by an urban transportation network. Since their computational burdens are reasonable, they can be applied at the urban scale using a GIS.     

Exploring Spatial Patterns Using an Expanded Spatial Autocorrelation Framework

Spatial autocorrelation (SA) is regarded as an important dimension of spatial pattern. SA measures usually consist of two components: measuring the similarity of attribute values and defining the spatial relationships among observations. The latter component is often represented by a spatial weights matrix that predefines spatial relationship between observations in most measures. Therefore, SA measures, in essence, are measures of attribute similarity, conditioned by spatial relationship. Another dimension of spatial pattern can be explored by controlling observations to be compared based upon the degree of attribute similarity. The resulting measures are spatial proximity measures of observations, meeting predefined attribute similarity criteria. Proposed measures reflect degrees of clustering or dispersion for observations meeting certain levels of attribute similarity. An existing spatial autocorrelation framework is expanded to a general framework to evaluate spatial patterns and can accommodate the proposed approach measuring proximity. Analogous to the concept of variogram, clustergram is proposed to show the levels of spatial clustering over a range of attribute similarity, or attribute lags. Specific measures based on the proposed approach are formulated and applied to a hypothetical landscape and an empirical example, showing that these new measures capture spatial pattern information not reflected by traditional spatial autocorrelation measures.     

基于网络分析的交通网络评价及其与区域经济发展关系研究

以网络分析为基础,使用节点连通性和可达性等指标,评价研究甘肃省的交通网络以及交通网络与区域经济发展之间的内在关系,提出了平均经济--网络直径概念、功能及其计算方法。研究结果表明,节点连通性和可达性指标与区域经济发展水平具有密切的相关性,且跨区域交通对区域经济发展的贡献率大于仅邻域交通对区域经济发展的贡献率;使用节点连通性和可达性指标可界定出各区域经济之间的空间相互作用范围,为整个区域的交通规划和经济区划提供有力的科学依据;甘肃省交通呈聚团模式,具有空间自相关性。     

Accessibility Measurement in Transportation Networks and Application to the Seoul Bus System

This study presents an algorithm for measuring the time‐distance accessibility based on the flow data of actual transportation networks and examines resulting accessibility distributions. Specifically, we construct an extended graph of the transportation network to take into account not only the average speed and transfer time extracted from the data set but also various possible trajectories taken via transfers. Employing the modified Floyd algorithm which finds the shortest time distance, we compute the time‐distance accessibility of every bus stop in the Seoul bus system, which yields distinctive skew distributions. We then introduce a time‐distance cutoff to focus on effective connections and probe the emergent spatial distributions as the cutoff is varied. Revealed are the characteristic scales as well as spatial structures of the system. It is suggested that the time‐distance accessibility can serve as a significant measure to describe and predict the urban land use pattern.     

Quantifying the defensiveness of defended sites on the Northwest Coast of North America

Defensive architectural features are used to evaluate the scale and pervasiveness of conflict in antiquity around the world, but in the archaeology of conflict on the Northwest Coast, the relationship between physical landscapes, built defensive features and warfare has never been tested using quantifiable measures. We argue here that the syntax of biomechanical control, reflecting the universality of the parameters of the human body, is inherent in architectural analyses of conflict, and develop an index of defense (DI) based on commonly invoked constituent measures of defensiveness. The DI is represented in a single value, derived from four individual measures (visibility, elevation, accessibility and area), each with constituent variables. We test this quantitative measure using a sample of identified defensive and non-defensive sites on the Northwest Coast of North America in order to evaluate this system of quantifying the contribution of site location and architectural features to the overall defensiveness of communities and discuss some of the implications of this measure on interpreting the role of conflict on the Northwest Coast.