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1.
Conventional accessibility measures based on the notion of locational proximity ignore the role of complex travel behavior and space–time constraints in determining individual accessibility. As these factors are especially significant in women's everyday lives, all conventional accessibility measures suffer from an inherent “gender bias.” This study conceptualizes individual accessibility as space–time feasibility and provides formulations of accessibility measures based on the space–time prism construct. Using a subsample of European Americans from a travel diary data set collected in Franklin County, Ohio, space–time accessibility measures are implemented with a network-based GIS method. Results of the study indicate that women have lower levels of individual access to urban opportunities when compared to men, although there is no difference in the types of opportunities and areas they can reach given their space–time constraints. Further, individual accessibility has no relationship with the length of the commute trip, suggesting that the journey to work may not be an appropriate measure of job access.  相似文献   

2.
Although recent studies of individual accessibility have used detailed representations of urban street networks, unrealistic measures of travel time based on assumptions about constant travel speeds through the network were often used. Utilizing constant travel times does not allow for daily congestion and assumes that the effects of congestion are uniform throughout the city and affect all people equally. This research measures individual space‐time accessibility in order to show that the incorporation of locally specific travel times within a street network allows a significant increase in the ability to realistically evaluate individual accessibility within cities. The results show that the accessibility of individuals within cities is not homogenous, and neither does access to employment or shopping opportunities vary according to common expectations about urban form and human behavior. Instead, the role of distance in predicting accessibility variations within cities is quite limited. This article also shows that incorporating time into accessibility measures in the form of congestion and business hours leads to additional (and highly spatially uneven) reductions in accessibility, revealing that the temporal dimension is very important to accurately assessing individual accessibility.  相似文献   

3.
Although recent studies of individual accessibility have used detailed representations of urban street networks, unrealistic measures of travel time based on assumptions about constant travel speeds through the network were often used. Utilizing constant travel times does not allow for daily congestion and assumes that the effects of congestion are uniform throughout the city and affect all people equally. This research measures individual space-time accessibility in order to show that the incorporation of locally specific travel times within a street network allows a significant increase in the ability to realistically evaluate individual accessibility within cities. The results show that the accessibility of individuals within cities is not homogenous, and neither does access to employment or shopping opportunities vary according to common expectations about urban form and human behavior. Instead, the role of distance in predicting accessibility variations within cities is quite limited. This article also shows that incorporating time into accessibility measures in the form of congestion and business hours leads to additional (and highly spatially uneven) reductions in accessibility, revealing that the temporal dimension is very important to accurately assessing individual accessibility.  相似文献   

4.
Spatial access to healthy foods has drawn growing attention regarding the relationship with people's health conditions and demographic and socioeconomic characteristics. Individuals' differences and the impact of travel behaviors on food accessibility, however, are rarely studied. This study incorporates mobility, time, and transportation mode components to measure each individual's access to healthy foods. We employed three activity space measures to estimate food accessibility: route network buffer, time-weighted standard deviational ellipse (SDE), and mode-weighted SDE. Food accessibility in three activity spaces shows similar variabilities. Geographic size and spatial access to healthy foods differ significantly by income and employment for all three activity space measures. People with higher incomes and those who are currently employed are likely to have larger activity spaces and higher food accessibility. As age increases, people tend to increase their size of activity spaces (in both SDE measures) and food accessibility significantly. Females are likely to have smaller activity spaces and less accessibility to healthy foods (only in the time-weighted SDE measure). Geographic size and spatial access do not differ significantly by education and number of vehicles per household. Although three activity spaces are highly correlated in both geographic size and spatial access, differences still exist among them.  相似文献   

5.
Highly technological in vitro fertilization (IVF) treatment is available at relatively few medical centers in rural United States. This research derives a spatial accessibility surface for IVF centers in a rural Midwestern state through the application of computational methods that consider spatial and non-spatial parameters to discover potentially underserved areas in the state. These methods include a modified gravity model and techniques from spatial interaction modeling. The approach develops an enhanced accessibility index that incorporates three key sociodemographic variables describing patients seeking infertility healthcare in Iowa that have been identified based on a survey of IVF care practitioners in the state. Self-organizing map techniques are used to reveal cluster locations based on the degree of match between census sociodemographic data and the expert-identified variables. The spatial accessibility surface is combined with the sociodemographic clusters to define an enhanced measure of spatial accessibility. The results suggest that while the state's IVF centers are located in tracts characterized by high spatial accessibility, at least 19% of patients travel from census tracts classed as moderate to low accessibility. This result reveals some opportunities for service improvements for these locations. Interestingly, for tracts that are characterized as having a lower patient sociodemographic match, high spatial accessibility does not appear to be a factor that improves the likelihood of patient care, at least for the variables investigated as part of this research.  相似文献   

6.
可达性研究的回顾与展望   总被引：84，自引：10，他引：74  
可达性是指利用一种特定的交通系统从某一给定区位到达活动地点的便利程度。可达性反映了区域与其他有关地区相接触进行社会经济和技术交流的机会与潜力。本文综合了可达性的主要定量评价方法,并对各种方法的优缺点进行了比较,总结了近期可达性评价方法的进展与动态。随后分别在区域和国家尺度与城市内部尺度上总结了可达性在区域经济发展研究、城市土地利用、社会服务设施提供、城市社会问题等各方面的应用。相对来讲,国内关于可达性的研究尚不丰富。最后,本文阐述了目前可达性研究中的问题,并对未来研究进行了展望。  相似文献   

7.
Active participation in the outdoors not only provides enjoyment and adventure, but it is also important for health and promoting conservation values. The latter is particularly important for young people as they are at an impressionable stage in their lives. Geographical accessibly of recreation opportunities can be a major barrier to utlization of the New Zealand outdoors. While it would be ideal to have a variety of opportunities available to everyone regardless of residence, the distribution of opportunities is constrained by the extent of suitable lands. This research provides a population based assessment of the geographical accessibility of recreational opportunities. Accessibility has many dimensions and includes cultural, financial, and geographical barriers; therefore this research is only addressing one dimension of accessibility. Geographical Information Systems is used for the analysis, which involves a function called least-cost path analysis. This identified the travel time (using a private vehicle) via the quickest route from where people live (represented by census enumeration points) to the entry point of the recreation sites. The outputs of this research are maps and spatial statistics on the travel times to a range of recreation opportunities for different parts of New Zealand. This information is important for recreation planning. In addition, the information also provides research opportunities for modelling recreation use, especially when accessibility information is combined with landscape experience information and recreation usage statistics.  相似文献   

8.
Constraint‐based models and models constructing accessibility measures mainly focus on single agents having only one available transport mode. However, numerous cases exist where multiple agents or groups of individuals with different available transport modes want to participate in a joint activity at a certain location. The aim of this paper is to provide new insights into representing and reasoning about feasible space–time opportunities for multiple agents. Relying on concepts of time geography, we propose a conceptual framework in order to determine interaction spaces for groups of individuals. Besides availability of means of transport and the locations of each individual, minimum activity duration and opening hours of opportunities are taken into account. The reasoning about space and time is visualized in three dimensions using a hybrid (CAD/GIS) system.  相似文献   

9.
Travel time uncertainty has significant impacts on individual activity-travel scheduling, but at present these impacts have not been considered in most accessibility studies. In this paper, an accessibility evaluation framework is proposed for urban areas with uncertain travel times. A reliable space-time service region (RSTR) model is introduced to represent the space-time service region of a facility under travel time uncertainty. Based on the RSTR model, four reliable place-based accessibility measures are proposed to evaluate accessibility to urban services by incorporating the effects of travel time reliability. To demonstrate the applicability of the proposed framework, a case study using large-scale taxi tracking data is carried out. The results of the case study indicate that the proposed accessibility measures can evaluate large-scale place-based accessibility well in urban areas with uncertain travel times. Conventional place-based accessibility indicators ignoring travel time reliability can significantly overestimate the accessibility to urban services.  相似文献   

10.
Quantitative measures of accessibility are increasingly used in land cover change modeling and in assessing human pressure on the environment. In riverine Amazonia the significance of physical accessibility for biodiversity, land use patterns and economic livelihoods is widely acknowledged, but attempts to quantify accessibility in practice have been few in number. In this study we compare different distance- and frequency-based measures of spatial accessibility and develop a quantitative model of accessibility patterns for the north-eastern Peruvian Amazonia where rivers form the core of the transportation network. We model accessibility between the rural areas of the Loreto region and the capital city of Iquitos, using different distance algorithms in a geographic information system, and complement the distance model with information on river boat frequencies and transport capacities. Patterns of accessibility are visualized in terms of potential production zones for different types of agricultural and non-timber forest products.This study demonstrates how results from different accessibility measures vary considerably. The mean Euclidean distance to Iquitos is almost 270 km, the mean network distance nearly 760 km and the mean travel time 70 h. Observed network distances from validation points to Iquitos are on average 1.6 times longer than Euclidean distances, and for the whole study area, the average ratio between modeled network distances and Euclidean distances is 3.1. The correlation between network distances and time distances is very strong, but time distances are relatively shorter along the major channels where boat traffic is considerably faster than along narrow, tightly meandering rivers. Measures of boat frequency and transport capacity show that availability of transport possibilities is highly varying across the region. These measures provide insights into the ’thickness’ of trade, indicating the level of market integration for riverine settlements. We conclude that quantifying accessibility in an environment like Peruvian Amazonia requires measures that take into account the spatial structure and dynamic nature of the riverine transportation network. Time as a unit of distance provides the most relevant measure of accessibility in the Amazonian context, where many human actions and traditional livelihoods are controlled by travel times between the regional core and the hinterland.  相似文献   

11.
The temporal dimensions of public transit accessibility have recently garnered an increasing amount of interest. However, the existing literature on transit accessibility is heavily based on oversimplified assumptions that transit services operate at deterministic speeds using predetermined timetables. These measurements may overestimate transit accessibility, especially for large metropolitan areas where inter- and intra-modal transfers are frequent. To handle travel time uncertainty, a multi-modal transit accessibility modeling approach is proposed to account for realistic variations in travel time and service reliability. The proposed approach is applied to the mapping of transit accessibility in Shenzhen (China), where transit services exhibit significant travel time variations over space and time. Compared to traditional transit accessibility measures, our method has been demonstrated to better capture intrinsic spatial and temporal accessibility variations with complex multi-modal transit networks. Normal distribution of inter-stop travel times and constant travel speed between GPS sampling points are assumed to simply the computation, which we consider to adjust in future studies to better quantify the dynamics of transit accessibility across space and time.  相似文献   

12.
Today, the opportunity for potential human activity has gone beyond physical space to virtual space. Based on a proposed conceptual framework that models the relationships between physical and virtual spaces, this paper presents an attempt to adjust the space–time prism concept of Hägerstrand's time geography to identify potential activity opportunities in virtual space, focusing on the virtual space access channels available in physical space. A three‐dimensional (3D) spatio‐temporal Geographic Information System (GIS) design has been developed in this research to accommodate the adjusted space–time prism concept to support the representation, visualization, and analysis of potential human activities and interactions in physical and virtual spaces using the prism representation. Following the design, a prototype system has been successfully implemented in a 3D GIS environment. Such a system can provide powerful analytical tools for studies related to potential human activities and applications such as location‐based services (LBS) and accessibility analysis in the information age.  相似文献   

13.
吴江洁  孙斌栋 《地理研究》2015,34(9):1744-1754
基于第六次人口普查、第二次经济普查和问卷调查数据,定量描述和分析了上海都市区内部以街道为空间尺度的就业可达性及其空间格局,探讨了劳动者的工资收入与居住区位就业可达性的关系。结论表明：上海市的居民就业可达性呈现相对均衡的多中心分布格局,与北京就业可达性单中心的分布格局有明显的不同。同时,在控制个人经济社会属性和地区属性的条件下,上海的居民就业可达性对居民个人收入水平具有显著的正向影响。这一结论的政策含义是,地理区位较差的住房有损于居民收入,可能是吸引力不足的重要原因之一;政府通过提高地区的居民就业可达性,有助于改善就业机会,促进居民个人收入的增加。  相似文献   

14.
This study examines spatial accessibility of pharmacies in Baton Rouge, Louisiana. Two popular geographic information systems (GIS)—based methods are compared: the proximity method uses the distance (travel time) from the nearest pharmacy, and the two‐step floating catchment area (2SFCA) method considers the match ratio between providers and population as well as the complex spatial interaction between them. The study indicates that disproportionally higher percentages of African‐Americans are in areas with shorter travel time to the nearest pharmacies than whites, but suffer from poorer accessibility measured by the 2SFCA method—that is, fewer pharmacies per 10,000 residents. Seniors, particularly those of seventy‐five years or older, tend to be disproportionally concentrated in areas that not only are closer to pharmacies, but also have more pharmacies per 10,000 residents. The two methods used in the study capture different elements in spatial accessibility: one being physically close to a facility and another adding the crowdedness in service. Both properties can be valuable for residents. The two may not always coincide with each other in spatial variability, as it is the case for racial disparity in our study area. However, when they do, as in the case for seniors, it may imply a true (dis)advantage for a demographic group in terms of both properties of spatial accessibility.  相似文献   

15.
可达性是指从一个地方到另一个地方的容易程度,目前主要运用距离度量法、拓扑度量法、重力度量法、累积机会法等传统度量方法,应用于人文地理学、区域与城市规划等相关研究领域当中.该研究以ArcGIS Desktop 9.2平台为技术支撑,通过对影像数据、图形数据以及社会经济等属性数据进行整理来构建矢量数据库(geodatabase),运用GIS矢量和栅格数据的空间分析模块,采用时间成本加权距离方法,对扬中市过江通道建成前后的可达性变化进行了分析.该方法突破了传统的描述性研究,通过进行等时圈分析可以得到节点城市影响腹地的范围,并且可以精确统计出通勤覆盖范围的地域面积、人口规模和经济规模,为地区资源的合理配置提供更为科学的依据.  相似文献   

16.
Many geographic studies use distance as a simple measure of accessibility, risk, or disparity. Straight-line (Euclidean) distance is most often used because of the ease of its calculation. Actual travel distance over a road network is a superior alternative, although historically an expensive and labor-intensive undertaking. This is no longer true, as travel distance and travel time can be calculated directly from commercial Web sites, without the need to own or purchase specialized geographic information system software or street files. Taking advantage of this feature, we compare straight-line and travel distance and travel time to community hospitals from a representative sample of more than 66,000 locations in the fifty states of the United States, the District of Columbia, and Puerto Rico. The measures are very highly correlated (r 2 > 0.9), but important local exceptions can be found near shorelines and other physical barriers. We conclude that for nonemergency travel to hospitals, the added precision offered by the substitution of travel distance, travel time, or both for straight-line distance is largely inconsequential.  相似文献   

17.
Accessibility is an important consideration in sustainable mobility policies, particularly for transit users. Measures suggested in the literature are based on coarse aggregate spatial resolution of traffic analysis zones that is sufficient for managing car travels only. To reflect a human door-to-door travel, transit accessibility demands an explicit view of the location of origin, transit stops and destination, as well as of the temporal fit between transit lines timetable and traveler’s needs. We thus estimate transit accessibility based on mode-specific travel times and corresponding paths, including walking and waiting, at the resolution of individual buildings and stops. Car accessibility is estimated at a high resolution too. A novel representation of transit network as a graph is proposed. This representation includes all modal components of a transit travel – walking, waiting at a stop, transit ride, transfers between lines, thus enabling unified view of a travel, regardless of mode. The use of modern high-performance graph database allows construction of high-resolution accessibility maps for an entire metropolitan area with its 100–200 K buildings. The application is tested and applied in a case study involving the evaluation of the 2011 bus line reform in the city of Tel Aviv. Specifically, we demonstrate that while the reform increased the average accessibility for the entire city the increase was not uniform with different areas of the city experiencing different absolute accessibility by transit and relative accessibility in comparison to car travel. The bus reform did in fact benefit travelers that experienced low relative accessibility, but the benefits are mainly accruing to longer trips. Our approach and computational methods can be employed for directly investigating the impacts of transportation infrastructure investments.  相似文献   

18.
《Urban geography》2013,34(6):543-560
With recent advances in information and communications technologies (ICT), traditional conceptualizations and models of spatial interaction need updating. In a previous paper, this author developed an analytical framework that incorporated telecommunications capabilities as well as transportation modes and residential and work locations into a unified representation of the “geography of opportunities” (Shen, 1999). In this paper, the initial framework is extended by the inclusion in the formulation not only of employment opportunities, but also of other types of opportunities. Each type of opportunities is distributed among three components of geographic space: the physical space, the hybrid space, and the virtual space. The effects of ICT are captured by: (1) the saving of travel time for people who can partially substitute telecommunications for transportation as means to access opportunities in virtual and hybrid spaces and (2) the migration of opportunities from physical space to virtual and hybrid spaces. Individuals' position in the emerging spatial structure of the information society is measured in terms of accessibility to a wide range of economic and social opportunities. This new approach is shown to be an operational and promising analytical tool in a hypothetical setting. However, its refinement and application is currently constrained by the lack of systematically collected data on many aspects of the human geography. [Key words: telecommunications, human geography, spatial structure, spatial analysis.]  相似文献   

19.
This study analyses the socioeconomic and demographic make‐up of Koreans in Los Angeles metropolis, the largest hub of Koreans in the United States, to better understand the decentralized concentration of Koreans by addressing their within‐ and among‐group variations. By employing the rarely used measures of correspondence and typology analyses, we delineate the boundaries for Korean clusters using Getis and Ord G* local statistic, wherein each cluster's neighborhood and demographic characteristics are compared to gain nuanced insights of within‐group variations, and its evolution during 1970–2010. Cluster level analysis of Koreatown suggests that even though it was classified as a Korean cluster, Korean Americans were unevenly distributed across these clusters, with underrepresentation in white‐dominant neighborhoods, whereas much of their intraurban spaces were shared with Hispanics. All clusters except extended Koreatown exhibited Li's ethnoburb‐style spatial patterns. The Koreatown and suburban clusters were also distinct in terms of their demographic/ethnic, socioeconomic, educational, age/life cycle, and housing characteristics, suggesting socio‐spatial polarization. Our analysis, challenges the commonly perceived notion of Koreans being a homogenous group and Asians being model minorities. We illustrate significant within‐group differences among the Koreangelos. We, thus, propose innovative measures to analyze population groups to flesh out rich narratives of America's fast changing social geographies.  相似文献   

20.
It is essential to ensure equal accessibility to services, such as sport and recreation facilities or green and water environments. Differences in accessibility can potentially cause negative health and social welfare implications. Accessibility and service area analyses from the perspective of access equality are typically rather simple. They are often based on arbitrary travel-distance thresholds and made only with a single mode of transport in mind. Thus, they exclude the multidimensional nature of accessibility where individuals' travel behavior and perceived accessibility also play an important role. In this paper, a PPGIS method was used to empirically investigate distances and durations that respondents travel with different modes of transport to access popular water environments. Service area analyses were built on person-based and objectively measured threshold values that not only take into account the spatio-temporal elements of transport networks and a land use component but also recognize the requirements and preferences of individuals and their capacity to access and participate. The results showed that the most common mode of transport to access waters is walking. Generally, the residents travel by foot for 1.7 km to access water environments. Cars were found as the second most common mode of transport used, and most of the popular water environments are accessible by car from every corner of the study area in a given travel threshold time. The results demonstrate the importance of deriving local parameters and the potential of the PPGIS approach for accessibility and service area delineation.  相似文献   

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