基于改进潜能模型的就医空间可达性度量和缺医地区判断——以江苏省如东县为例

潜能模型广泛应用于就医空间可达性评价,现有模型综合了医疗设施服务能力、居民点人口数量、医疗设施与居民点之间的出行阻抗。在此基础上通过考虑"医疗设施不同等级规模对居民就医选择行为的影响"对模型进行修正。结果表明,改进的潜能模型能够更为合理地评价就医空间可达性,准确揭示居民实际所能获取的医疗资源,结合医疗资源配置相关标准,则能有效判定缺医地区,为政府相关部门规划决策提供依据。     

基于最优供需分配的公共设施空间可达性分析

空间可达性是衡量公共服务设施公平性的重要指标,在医疗、教育、休闲等公共服务的布局规划中得到广泛应用。然而已有设施服务可达性模型难以充分反映服务供需关系,计算指标也缺乏物理意义。本文提出新的最优供需分配的公共设施空间可达性计算方法（OSD）取代现有方法。该方法基于最优供需分配模型,将设施服务分配给需求者,根据分配结果计算空间可达性指标。给定服务设施与需求的空间分布,以最小化旅行成本为目标,顾及设施服务能力,采用经典的运输问题模型确定最优的服务供需分配方案,进而度量服务的空间可达性。以郑州市金水区社区卫生服务为例,求解25个中心与1333个居住小区的最优服务配置。使用最优配置结果确定每个设施的服务范围、每个居住小区使用服务的旅行时间,以及特定时间阈值的服务覆盖比率。与流行的两步移动搜索法相比,新方法的计算指标具有明确的物理意义。本文提出的可达性评价方法无需参数,计算高效,结果易于解释,在公共服务评价及设施布局规划方面具有应用潜力。     

基于潜能模型的医疗设施空间可达性评价方法

空间可达性是评价医疗设施布局合理与否的重要指标,传统的医疗设施空间可达性评价,或者从医疗服务供需状况着手,或者从供需双方之间距离因素着手,均无法全面评价居民实际所能获取的医疗资源。本文采用基于潜能模型的评价方法对江苏省如东县医疗设施空间可达性进行分析研究,该方法综合考虑了医疗设施服务能力、居民点人口数量、医疗设施与居民点之间的出行阻抗。研究表明,通过选取合适的出行摩擦系数,该方法能够较为全面准确地测度较小研究单元的医疗设施空间可达性,辅以GIS技术,可以很直观地揭示研究区域内医疗设施空间可达性差异,结合公共卫生管理部门制定的医疗资源配置标准,还可较为准确判定缺医地区,为政府相关部门规划决策提供依据。     

就医空间可达性分析的两步移动搜索法——以江苏省东海县为例

精确评价医疗设施可达性的空间分异样状况是合理配置医疗资源的前提。本文在回顾国内外关于医疗空间可达性研究的基础上, 采用两步移动搜索法, 以江苏省贫困县--东海县为案例, 以行政村和医院为分析单元, 基于迪卡斯特拉算法计算出各村到医院(卫生院)的最短通行时间, 进而分析各村医疗空间可达性分异情况。采用不用服务时间阈值范围进行空间敏感性分析, 综合研判缺医地区分布特点。与传统的医卫人员和人口比值的方法相比, 两步移动搜索法能有效显示县域范围内医疗可达性的空间分异情况。采用较大的时间阈值, 医疗空间可达性分异较为平滑, 采用较小服务阈值则空间分异显著, 缺医范围也较大。东海县医疗空间可达性整体呈单核结构, 并沿主要交通线延伸, 缺医地区多分布于边缘乡镇。提高边缘乡镇的行政村的甲级卫生院等级和乡村道路等级将会改善边缘乡镇的就医可达性。     

A relative spatial access assessment approach for analyzing potential spatial access to colorectal cancer services in Texas

The usefulness of gravity-based spatial access models is limited because of the uncertainty introduced by the range of values of the impedance coefficient. To solve this problem, this paper proposes the concept of spatial access ratio (SPAR) derived from the enhanced 2-step floating catchment area (E2SFCA) method — a recent extension of the gravity model — to assess potential spatial access. First, a sensitivity assessment is conducted to verify the effectiveness of SPAR and its advantages in overcoming the uncertainty problem. Then, the E2SFCA method and the shortest travel time method are employed to measure potential spatial access to colorectal cancer (CRC) prevention and treatment services in Texas based on data at the census tract level. The socio-demographic and geographic distributions of potential spatial access to CRC services are also examined. The sensitivity assessment reveals substantial fluctuations in the values of the spatial access index calculated directly by the E2SFCA method under different values of the impedance coefficient. However, the values of SPAR remain stable under different values of the coefficient. A comparative analysis indicates that potential spatial access to primary care physicians (PCPs), CRC screening facilities, and oncologists varied among different racial/ethnic and socioeconomic population groups as well as in different geographic regions in Texas. Non-Hispanic blacks, Asians, and people in affluent areas had a geographical advantage in accessing CRC services than other groups. The urban/rural difference was more obvious and serious than those of different racial/ethnic groups and groups with different socio-economic statuses, as metropolitan residents had more than three times the potential spatial access than isolated rural residents.     

Take the edge off: A hybrid geographic food access measure

Measures of geographic food access overlook an important source of statistical biases, termed the edge effect. The edge effect refers to the fallacy that events contributing to the spatial pattern of an analysis unit may be outside of that unit; thus merely summarizing events within the unit may lead to distortion of the estimation. Food procurement activities can happen beyond existing administrative boundaries. Delineating food access using unit-based metrics may misrepresent the true space within which food stores are accessible. To overcome this problem, this paper proposes a gravity-based accessibility measure to improve unit-based statistical approaches in food access research. In addition, this method accounts for the spatial interaction between food supply (e.g., food items in stock) and demand (e.g., population) as well as how this interaction is mediated by the spatiotemporal separation (e.g., travel time, modality). The method is applied to the case of Franklin County, OH and has revealed the food access inequity for African Americans by modes of transport, including walking, biking, and driving. The analysis of the correlation between mode-specific food access and socioeconomic status (SES) variables reveals that using a single modality in food access research may not fully capture the travel behavior and its relationship with local food environments. With modifications, the proposed method can help evaluate food access for a target population group, such as Supplemental Nutrition Assistance Program (SNAP) users or selected ethnic minorities who may face acute difficulties in procuring economically affordable and culturally appropriate foods.     

Quantifying multi-modal public transit accessibility for large metropolitan areas: a time-dependent reliability modeling approach

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.     

Geographical accessibility and Kentucky's heart-related hospital services

Cardiovascular diseases (CVDs) are a leading cause of mortality in the US. Rates of mortality vary spatially and demographically, influenced not only by individual patient characteristics but also by levels of accessibility to hospital services and facilities. In 2000, Kentucky ranked third in the nation for heart-related deaths. The purpose of this paper is to assess geographical accessibility and service utilization related to ambulatory care sensitive CVDs in Kentucky. This study utilizes the Kentucky Hospital Discharge Database to evaluate service utilization and the Compressed Mortality File to examine mortality related to CVDs. A spatial statistical comparison of the geographical distribution of service usage and travel time to hospitals assists in assessing the relationship between accessibility and health. Our findings suggest that the distribution of utilization and mortality is geographically variable. People living in rural areas travel further to services; populations residing more than 45 min from health facilities are more likely to be socially and economically marginalized. Spatial clustering of high rates of hospital utilization occurs in areas with lower accessibility.     

Accessibility in designing centralised warehousing: Case of health care logistics in Northern Finland

Long distances and sparse service networks set challenging conditions for material logistics in health care. Globally, health care organisations have been making structural changes towards centralised warehousing and deliveries. In Northern Finland, material logistics of the public health care system rely mainly on numerous separate order and delivery systems, although logistics needs, ordering and stock in different health care facilities correspond to each other. As centralised logistics in orders and deliveries may lead to remarkable savings, pressure for centralised management is high. This paper analyses how effectively a potential centralised warehousing system can be organised based on its spatial components. These include optimal location of one or more warehouses, delivery network coverage and efficiency of routes, as well as accessibility of health centres and hospitals. The geographic information systems (GIS) -based accessibility analytical framework described in this study applies vehicle routing and heuristic computations to location-allocation of warehouses to potential sites by optimising transport cost with a constraint to provide service to at least 90% of delivery demand. The spatial data include the road network, health care facility locations with rough estimates of freight demand nodes and potential locations of warehouse facilities. The main findings of the study show that majority of health centres and hospitals can be effectively reached by a delivery network based on one or two warehouses. Furthermore, the efficiency of the delivery network does not increase remarkably by increasing the number of warehouses, when measured as driving time.     

Simulating visit probability distributions within planar space-time prisms

The space-time prism is key concept in time geography and moving objects databases; it demarcates all locations that a mobile object can occupy given anchor locations and times and a maximum velocity for travel. Although the prism’s spatial and temporal extent is widely applied as a measure of accessibility and object locational uncertainty, until recently little attention has been paid to the properties of the prism interior such as the probabilities of the object visiting different locations within the prism. Better understanding of the visit probability distribution within the prism can improve theoretical understanding as well as refine the prism as a practical measure of space-time accessibility and object uncertainty. This paper presents two methods for modeling the distribution of visit probabilities within planar space-time prisms: (1) a directed Random Walk method for discrete space and time, and (2) a truncated Brownian Bridges method for continuous space and time. We illustrate these methods and demonstrate the effect of prism and mobility parameters on the visit probability distributions within the prism.     

An enhanced approach for modeling spatial accessibility for in vitro fertilization services in the rural Midwestern United States

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.     

Measuring place-based accessibility under travel time uncertainty

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.     

基于改进潜能模型的县域小学空间可达性研究——以湖北省仙桃市为例

空间可达性是评价教育设施布局合理性的重要指标,而潜能模型是度量教育设施空间可达性的重要方法。本文在引入学校服务能力因子的基础上,综合考虑学校服务能力等级影响和居民极限出行时间构建就学影响因子,对潜能模型加以改进。通过以湖北省仙桃市为典型县域单元的案例研究,结果表明：①村级居民点尺度,乡镇中心和高等级公路沿线居民点的小学空间可达性普遍较高,并按照一定的半径范围呈距离衰减过程,而乡镇毗邻地区居民点的小学空间可达性相对较差;②乡镇(街道)尺度,可达性较高的乡镇(街道)主要分布在沿G318的北部地区,且城乡间、主城区与城郊的小学空间可达性均存在一定差距;③改进潜能模型能合理地评价各农村居民聚落点和各乡镇的小学空间可达性,当摩擦系数β取值为2时,能更为准确地揭示农村居民所能获取的教育资源,为相关部门决策提供科学依据。     

基于改进两步移动搜索法的县域医疗卫生服务空间可达性研究

针对县域医疗卫生服务设施的空间布局问题,应用改进两步移动搜索法对德清县医疗卫生服务的空间可达性进行评价。具体改进包括：引入核密度型距离衰减函数对两步移动搜索法进行扩展、考虑医疗设施资源的未充分利用、对不同规模等级医疗机构设置不同服务阈值。计算结果表明：① 浙江省德清县域医疗卫生服务空间可达性呈圈层式空间分布特征,高可达性区域主要集中于县城及邻接区域,边缘地区缺医明显;② 基于改进两步移动搜索法和传统两步移动搜索法的可达性计算结果具有不同的整体特征,但前者可达性计算结果及空间分布更符合实际。     

高铁对旅游者目的地选择的影响——以京沪高铁为例

通过因子分析降维得到影响旅游目的地选择的主要因素,包括旅行时间、旅游地的旅游资源禀赋、旅游地的交通通达性、旅游地的服务设施系统等4个指标;由此构建旅游需求—供给引力模型,测度高铁条件下主要因素对旅游者选择出游目的地的影响程度变化。结果显示：高铁开通前客源地和旅游地的空间距离是旅游目的地选择的最重要影响因素,且起到出游阻力影响;而高铁开通后主要影响因素对选择出游目的地的作用程度发生很大变化,客源地与旅游地的空间距离对出游阻力影响变得很小,而旅游地的交通网络密度、旅游资源禀赋和旅游服务接待能力成为重要的影响因素。研究结果可为高铁时代下旅游目的的地建设提供理论依据,以期在高铁条件下构建科学合理的旅游要素体系,实现旅游地系统升级优化。     

Modeling Spatial Accessibility of Immigrants to Culturally Diverse Family Physicians

This article uses accessibility as an analytical tool to examine health care access among immigrants in a multicultural urban setting. It applies and improves on two widely used accessibility models—the gravity model and the two-step floating catchment area model—in measuring spatial accessibility by Mainland Chinese immigrants in the Toronto Census Metropolitan Area. Empirical data on physician-seeking behaviors are collected through two rounds of questionnaire surveys. Attention is focused on journey to physician location and utilization of linguistically matched family physicians. Based on the survey data, a two-zone accessibility model is developed by relaxing the travel threshold and distance impedance parameters that are traditionally treated as a constant in the accessibility models. General linear models are used to identify relationships among spatial accessibility, geography, and socioeconomic characteristics of Mainland Chinese immigrants. The results suggest a spatial mismatch in the supply of and demand for culturally sensitive care, and residential location is the primary factor that determines spatial accessibility to family physicians. The article yields important policy implications.     

Critical distances: Comparing measures of spatial accessibility in the riverine landscapes of Peruvian Amazonia

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.     

基于陆路综合交通系统的中国城市网络通达性模拟及其对区域发展格局的影响

在中国经济社会发展和交通建设出现新转向的背景下,论文基于现状和相关规划完成后的陆路综合交通网络,解析了中国城市网络通达性的演化趋势及其对国土空间结构演进的影响,重点回应了“全国123出行交通圈”建设和国土开发均衡性2个问题。结果显示,已有规划的完成能够大幅提高中国城市网络的通达性水平,在最短旅行时间上基本可以支撑“全国123出行交通圈”的建设;通过促进轴—辐组织模式和空间级联秩序发育,已有规划能够引导国土开发结构朝多中心、网络化方向演进,为区域间的协调和均衡发展提供交通基础;未来应从支撑与引导、整合与衔接、效率与公平等方面持续优化交通服务的供给结构,提升综合交通运输体系服务人民生活和社会生产的能力。     

个体出行情景下上海中心城区地铁可达性研究

地铁是城市内重要的公共交通方式,对缓解交通压力、提高居民出行便捷度起到重要作用。个体通过地铁前往城市内不同地点的能力受个体前往地铁站的能力和地铁站间的通行能力影响。基于此,该文综合考虑个体可达性与地方可达性,提出评价个体到达区域内不同地点能力的指标——个体区域出行可达性,即从某点出发就近进入某类交通网络节点,通过该交通网络到达该网络所有节点的最短时间均值,可结合最短旅行时间及加权平均旅行时间计算得到,以尽可能精细地评价在节点分布足以代表区域的情形下个体到达整个区域的能力,并计算了上海中环以内城区地铁出行的个体区域出行可达性。结果表明:受线网结构和自然地物分布的影响,个体在上海中心城区通过地铁前往不同地点的能力由最中心地区向外波动下降,部分特殊地区和线网稀疏区个体出行能力较差,浦西地区的可达性情况明显好于浦东地区。     

基于改进潜能模型的城市医疗设施空间可达性——以上海市杨浦区为例

引入人口规模因子和医疗设施等级规模影响系数改进潜能模型,基于GIS空间分析技术,以上海杨浦区为例对其医疗设施空间可达性进行研究。结果表明：杨浦区医疗设施空间可达性分布不均,大桥街道、定海路街道及殷行街道部分区域医疗设施空间可达性较高;中部区域一些街道存在同等级医院位置密集、医疗资源相对集中的情况;杨浦区三级医院的居民就医空间可达性整体优于二级、一级医院。改进的潜能模型综合考虑了居民点人口数量、医疗设施与居民点之间的出行阻抗、以及医疗设施的等级规模对居民就医选择的影响,能更合理地评价医疗设施的可达性。研究结果可为城市医疗设施科学规划与决策提供依据。