Spatial Accessibility Measures Research Articles

Does the edge effect impact on the measure of spatial accessibility to healthcare providers?

BackgroundSpatial accessibility indices are increasingly applied when investigating inequalities in health. Although most studies are making mentions of potential errors caused by the edge effect, many acknowledge having neglected to consider this concern by establishing spatial analyses within a finite region, settling for hypothesizing that accessibility to facilities will be under-reported. Our study seeks to assess the effect of edge on the accuracy of defining healthcare provider access by comparing healthcare provider accessibility accounting or not for the edge effect, in a real-world application.MethodsThis study was carried out in the department of Nord, France. The statistical unit we use is the French census block known as ‘IRIS’ (Ilot Regroupé pour l’Information Statistique), defined by the National Institute of Statistics and Economic Studies. The geographical accessibility indicator used is the “Index of Spatial Accessibility” (ISA), based on the E2SFCA algorithm. We calculated ISA for the pregnant women population by selecting three types of healthcare providers: general practitioners, gynecologists and midwives. We compared ISA variation when accounting or not edge effect in urban and rural zones. The GIS method was then employed to determine global and local autocorrelation. Lastly, we compared the relationship between socioeconomic distress index and ISA, when accounting or not for the edge effect, to fully evaluate its impact.ResultsThe results revealed that on average ISA when offer and demand beyond the boundary were included is slightly below ISA when not accounting for the edge effect, and we found that the IRIS value was more likely to deteriorate than improve. Moreover, edge effect impact can vary widely by health provider type. There is greater variability within the rural IRIS group than within the urban IRIS group. We found a positive correlation between socioeconomic distress variables and composite ISA. Spatial analysis results (such as Moran’s spatial autocorrelation index and local indicators of spatial autocorrelation) are not really impacted.ConclusionOur research has revealed minor accessibility variation when edge effect has been considered in a French context. No general statement can be set up because intensity of impact varies according to healthcare provider type, territorial organization and methodology used to measure the accessibility to healthcare. Additional researches are required in order to distinguish what findings are specific to a territory and others common to different countries. It constitute a promising direction to determine more precisely healthcare shortage areas and then to fight against social health inequalities.

A spatio-temporal accessibility measure for modelling activity participation in discretionary activities

Accessibility is a key indicator for the number of opportunities experienced by an individual, and it is generally assumed that higher levels of accessibility lead to higher levels of activity participation and satisfaction. Despite the fact that this relationship has been tested in preceding studies, no clear pattern of correlation has been found between an individual’s accessibility and his/her participation in out-of-home discretionary activities. Previous studies mostly applied aggregate, spatial accessibility measures that do not account for the heterogeneity related to an individual’s spatio-temporal constraints. However, in addition to locations’ spatial distribution, personal constraints related to the mandatory activities a person undertakes – and therefore, his/her available time budget throughout the day – impact activity choices and scheduling. This paper proposes a disaggregate, person-based accessibility measure that takes spatial and temporal constraints into consideration for the travel behavior of 11,599 individuals in the Wasatch Front region, Utah. This method is compared to an aggregate, home-based accessibility measure to assess both methods’ ability to predict activity participation. The results show a highly significant, moderate correlation between the proposed person-based accessibility measure and participants’ surveyed partaking in discretionary activities. Both the model prediction and the locally weighted regression smoother indicate that the greatest change in participation occurs within the mid-range of accessibility levels, and not in the low end of the accessibility range as was expected. In addition, the home-based method shows a negative and highly significant relationship to activity participation, which indicates that aggregate accessibility measures may provide counterintuitive findings.

The Spatial Performance of Multi-Level Shopping Clusters A Case Study of Nanshan Commercial Cultural District

With the intensification of urban development in Chinese cities, mixed land use in urban centers extends vertically into 3-D and expands its scale from a single building to commercial clusters. The multi-level pedestrian system in city centers also changed its role from one of traffic isolation to spatial integration, where transit nodes, street sidewalks, squares, building entrances, atriums, and corridors are interconnected, both horizontally and vertically, into a whole spatial system, within which pedestrian flows are guided and shopping facilities are arranged. This paper uses spatial configuration analysis of space syntax to examine the impacts of spatial patterns on movement distribution and the business performance of tenant mix in the multi-level commercial system of the Nanshan Commercial Cultural District in Shenzhen, China. The key objective is to better understand the interactions between the socio-economic variables and spatial design parameters of a shopping complex. The research findings point to the importance of multiplicity between syntactic variables and other spatial variables in influencing the pedestrian flows, business performance and tenant mix in highly complex commercial systems. Particularly noteworthy is the relationship between spatial accessibility measures and the location of escalators, and the ways in which individual commercial buildings are embedded into the overall spatial system. The study suggests that this may lead to the preliminary identification of the spatial qualities of effective vertical extensions of mixed land use in a high-density urban settings.

수정 3SFCA 모형을 활용한 응급의료서비스 접근성 분석 : 충청남도를 사례로

수정 3SFCA 모형을 활용한 응급의료서비스 접근성 분석 : 충청남도를 사례로

Influence of Urban Multi-Criteria Deprivation and Spatial Accessibility to Healthcare on Self-Reported Health

Self-reported health is considered a health outcome related to neighborhood characteristics. This study analyzes the influence of urban multi-criteria deprivation and spatial accessibility to healthcare on individual self-reported health from a case study carried out in the city of Quito, Ecuador. A multi-criteria deprivation index and two alternative scenarios of this index were generated. A gravity-based measure of spatial accessibility to healthcare was also calculated. The neighborhood effects of deprivation measures and spatial accessibility to healthcare on individual self-reported health were evaluated by applying multilevel models. Significant neighborhood effects were found in two of the three applied multilevel models. This study contributes evidence of neighborhood effects on health outcomes, and can support urban planners and policy-makers in the reduction of urban health-related inequalities.

Does Spatial Access to Primary Care Affect Emergency Department Utilization for Nonemergent Conditions?

To examine the contributions of individual- and neighborhood-level spatial access to care to the utilization of emergency departments (EDs) for preventable conditions through implementation of novel local spatial access measures. Emergency department admissions data are from four HealthLNK member hospitals in Chicago from 2007 to 2011. Primary care physician office and clinic locations were obtained from the American Medical Association and the City of Chicago. Multilevel logit regression was used to model the relationship between individual- and neighborhood-level attributes and preventable ED use. Emergency department admissions data were classified based on the primary diagnosis for each encounter. Spatial access to care indices were generated in ArcGIS, and values were extracted at each ZIP code centroid to match patients' ZIP codes. Beyond sociodemographic factors such as gender and race, patients living in medically underserved areas (MUAs) and areas with lower spatial access to primary care clinics had higher odds of preventable ED use. Preventable ED use can be associated with sociodemographic characteristics, as well as spatial access to primary care services. This study reveals potential for using local measures of spatial accessibility for preventable ED analyses.

Associations of public transport accessibility with walking, obesity, metabolic syndrome and diabetes

Objective: To examine associations of public transport system accessibility with walking, obesity, metabolic syndrome and diabetes/impaired glucose regulation. Methods: Associations of public transport accessibility with self-reported walking for transport or recreation and measured biomarkers of chronic disease risk were estimated in 5241 adult residents of 42 randomly selected areas in Australia in 2004/05, drawn from the second wave of a population-based cohort study (AusDiab). Public transport accessibility was objectively measured using an adaptation of the Public Transport Accessibility Levels (PTAL) methodology, comprising both GIS derived spatial and temporal accessibility measures. Logistic regression models were adjusted for individual and environmental level covariates and clustering within areas. Results: Above median public transport accessibility was positively associated with a walking time of more than the median 90 min per week (OR=1.28, 95%CI 1.03, 1.60) and walking above the recommended 150 min per week (OR=1.35, 95%CI 1.11, 1.63). There were no associations of public transport accessibility with obesity (OR=1.05, 95%CI 0.85, 1.30), the metabolic syndrome (OR=1.09, 95%CI 0.91, 1.31) nor diabetes/impaired glucose regulation (OR=1.11, 95%CI 0.94, 1.30). Findings were similar for a subgroup reporting no vigorous recreational physical activity. Conclusions: In this Australian sample, public transport accessibility was positively associated with walking at recommended levels, including for people who are not otherwise vigorously active. Significance: Walking is crucial for increasing physical activity levels and population health, as well as maximising public transport system efficiency. Building evidence on public transport accessibility and walking will enable governments to exploit this important synergy.

Finding Food Deserts: A Comparison of Methods Measuring Spatial Access to Food Stores.

Public health research has increasingly focused on how access to resources affects health behaviors. Mapping environmental factors, such as distance to a supermarket, can identify intervention points toward improving food access in low-income and minority communities. However, the existing literature provides little guidance on choosing the most appropriate measures of spatial access. This study compared the results of different measures of spatial access to large food stores and the locations of high and low access identified by each. The data set included U.S. Census population data and the locations of large food stores in the six-county area around Chicago, Illinois. Six measures of spatial access were calculated at the census block group level and the results compared. The analysis found that there was little agreement in the identified locations of high or low access between measures. This study illustrates the importance of considering the access measure used when conducting research, interpreting results, or comparing studies. Future research should explore the correlation of different measures with health behaviors and health outcomes.

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 Space–Time Access to Food Retailers: A Case of Temporal Access Disparity in Franklin County, Ohio

Typical measures of food access use spatial-only methods to identify nearby food outlets and the quantity, quality, and variety of food available. This measure of spatial access falls short in explaining the effect that the operating hours of food retailers have on food access. Our study aims to complement the spatial dimension of access measures by bringing time in as a new constraint on food access. To this end, we developed three measures of spatial, temporal, and spatiotemporal access and correlated these measures with socioeconomic status (SES) in a case in Columbus, Ohio. Findings from our analysis of food access disparity suggest that low-SES neighborhoods in Columbus are not at a disadvantage of spatial access, but their limited temporal access is a more pressing concern. Implications drawn from the study would assist community advocates, local governments, and other stakeholders in deriving a better understanding of the local foodscape that are not only mediated by space but also time.

Measuring spatial accessibility to primary health care services: Utilising dynamic catchment sizes

The two-step floating catchment area (2SFCA) method continues to be a popular measure of spatial accessibility, especially in relation to primary-level health care. Despite its popularity, most applications of the 2SFCA method are limited by the utilisation of only a single catchment size within a small geographic area. This limitation is significant to health policies which are mostly applied at the state or national scale. In this paper, a five-level dynamic catchment size was trialled within the 2SFCA method to all of Australia, with a population's remoteness used to delineate increasing catchment sizes. Initial trial results highlighted two perverse outcomes which were caused by sudden changes in catchment sizes between each level. Further refinement led to trialling an additional three-level catchment sub-type to the 2SFCA method, which created a smoother transition between remoteness levels. This study has demonstrated an effective approach to dynamically apply variable and more appropriate catchment sizes into different types of rural areas, which for the first time enables the 2SFCA method to be suitable for national-level access modelling and its potential application to health policy.

A personalised semantic and spatial information retrieval system based on user's modelling and accessibility measure

Search personalisation is a multi-criteria decision problem whose objective is to filter out relevant information based on a set of criteria. Web personalisation can be seen as an interdisciplinary field whose objective is to facilitate the interaction between web content and users’ needs. The personalised search focuses on integrating users’ contexts, needs and relevancy criteria in the information retrieval process. This paper presents user’s modelling for personalised spatial and semantic information retrieval. The idea is to provide a user with personalised results based on his model and on the neighbour users’ models. The spatial personalisation search is based on a measure of spatial accessibility, whose objective is to predict and evaluate location relevancy, accessibility as well as associations at the user level. Experiments confirm the effectiveness of our proposal by pointing out the improvement of the personalised search results when compared to a baseline web search.

Spatial accessibility of drug treatment facilities and the effects on locus of control, drug use, and service use among heroin-injecting Mexican American men

BackgroundThis study explores the spatial accessibility of outpatient drug treatment facilities and the potential relationship with drug use-related outcomes among Mexican American heroin users. MethodsSecondary data on 219 current and former heroin-injecting Mexican American men aged 45 and older were drawn from a research study in Houston, Texas. We used geographic information systems (GIS) to derive two spatial accessibility measures: distance from one's place of residence to the closest drug treatment facility (in minutes); and the number of facilities within a 10-minute driving distance from one's place of residence. Exploratory logistic regression analyses examined the association between the spatial accessibility of drug treatment facilities and several drug use-related outcomes: internal locus of control (LOC); perceived chances and worries of injecting in the next six months; treatment utilization; and location of last heroin purchase. ResultsParticipants with greater spatial access to treatment programs were more likely to report a higher chance of injecting in the near future. However, while current heroin users were more worried about injecting in the next six months, greater spatial access to treatment programs seemed to have a buffering effect. Finally, those who lived closer to a treatment programs were more likely to have last purchased heroin inside the neighborhood versus outside the neighborhood. Spatial accessibility was not associated with internal LOC or treatment utilization. ConclusionThe findings showed that the presence of outpatient treatment facilities—particularly services in Spanish—may influence perceived risk of future heroin use and purchasing behaviors among Mexican American men. Implications for future spatially-informed drug use research and the planning of culturally and linguistically responsive drug treatment programs are discussed.

Estimating the effect of turn penalties and traffic congestion on measuring spatial accessibility to primary health care

Geographic variations in spatial accessibility to public resources, such as health care services, raise important questions about the efficiencies and inequities of the processes that determine where these services are located. Spatial accessibility can be measured many different ways, but many of methods in use today involve some measure of travel cost (in time or distance). In this study we explore a simple methodological question: how much are models of spatial accessibility influenced by the precise metric of travel cost? We address this question by comparing spatial accessibility to primary care physicians for two different methods of calculating travel cost (in time) on a street network: free-flow travel time and congested with turn penalties travel time—which augments free-flow travel times with the burden of traffic congestion and traffic intersection controls. We consider the effect of these two metrics of travel cost on a gravity-based measure of spatial accessibility to primary health care services in Edmonton, Alberta, Canada. Our results suggest that while travel times between locations of demand and locations of primary care providers greatly differ based on how travel cost is calculated, the gravity-based measure of spatial accessibility provides similar information for both travel cost metrics. Using congested with turn penalties travel time can be an onerous addition to the analysis of spatial accessibility, and is more useful for measuring absolute travel time rather than modeling relative spatial accessibility.

Spatial Access to Sterile Syringes and the Odds of Injecting with an Unsterile Syringe among Injectors: A Longitudinal Multilevel Study

Despite the 2010 repeal of the ban on spending federal monies to fund syringe exchange programs (SEPs) in the U.S.A., these interventions--and specifically SEP site locations--remain controversial. To further inform discussions about the location of SEP sites, this longitudinal multilevel study investigates the relationship between spatial access to sterile syringes distributed by SEPs in New York City (NYC) United Hospital Fund (UHF) districts and injecting with an unsterile syringe among injectors over time (1995-2006). Annual measures of spatial access to syringes in each UHF district (N = 42) were created using data on SEP site locations and site-specific syringe distribution data. Individual-level data on unsterile injecting among injectors (N = 4,067) living in these districts, and on individual-level covariates, were drawn from the Risk Factors study, an ongoing cross-sectional study of NYC drug users. We used multilevel models to explore the relationship of district-level access to syringes to the odds of injecting with an unsterile syringe in >75% of injection events in the past 6 months, and to test whether this relationship varied by district-level arrest rates (per 1,000 residents) for drug and drug paraphernalia possession. The relationship between district-level access to syringes and the odds of injecting with an unsterile syringe depended on district-level arrest rates. In districts with low baseline arrest rates, better syringe access was associated with a decline in the odds of frequently injecting with an unsterile syringe (AOR, 0.95). In districts with no baseline syringe access, higher arrest rates were associated with increased odds of frequently injecting with an unsterile syringe (AOR, 1.02) When both interventions were present, arrest rates eroded the protective effects of spatial access to syringes. Spatial access to syringes in small geographic areas appears to reduce the odds of injecting with an unsterile syringe among local injectors, and arrest rates elevate these odds. Policies and practices that curtail syringe flow in geographic areas (e.g., restrictions on SEP locations or syringe distribution) or that make it difficult for injectors to use the sterile syringes they have acquired may damage local injectors' efforts to reduce HIV transmission and other injection-related harms.

Spatial error in geocoding physician location data from the AMA Physician Masterfile: Implications for spatial accessibility analysis

The accuracy of geocoding hinges on the quality of address information that serves as input to the geocoding process; however errors associated with poor address quality are rarely studied. This paper examines spatial errors that arise due to incorrect address information with respect to physician location data in the United States. Studies of spatial accessibility to physicians in the U.S. typically rely on data from the American Medical Association’s Physician Masterfile. These data are problematic because a substantial proportion of physicians only report a mailing address, which is often the physician’s home (residential) location, rather than the address for the location where health care is provided. The incorrect geocoding of physicians’ practice locations based on inappropriate address information results in a form of geocoding error that has not been widely analyzed. Using data for the Chicago metropolitan region, we analyze the extent and implications of geocoding error for measurement of spatial accessibility to primary care physicians. We geocode the locations of primary care physicians based on mailing addresses and office addresses. The spatial mismatch between the two is computed at the county, zip code and point location scales. Although mailing and office address locations are quite close for many physicians, they are far apart (>20km) for a substantial minority. Kernel density estimation is used to characterize the spatial distribution of physicians based on office and mailing addresses and to identify areas of high spatial mismatch between the two. Errors are socially and geographically uneven, resulting in overestimation of physician supply in some high-income suburban communities, and underestimation in certain central city locations where health facilities are concentrated. The resulting errors affect local measures of spatial accessibility to primary care, biasing statistical analyses of the associations between spatial access to care and health outcomes.

Spatial accessibility of primary health care utilising the two step floating catchment area method: an assessment of recent improvements.

BackgroundThe two step floating catchment area (2SFCA) method has emerged in the last decade as a key measure of spatial accessibility, particularly in its application to primary health care access. Many recent ‘improvements’ to the original 2SFCA method have been developed, which generally either account for distance-decay within a catchment or enable the usage of variable catchment sizes. This paper evaluates the effectiveness of various proposed methods within these two improvement groups. Moreover, its assessment focuses on how well these improvements operate within and between rural and metropolitan populations over large geographical regions.ResultsDemonstrating these improvements to the whole state of Victoria, Australia, this paper presents the first comparison between continuous and zonal (step) decay functions and specifically their effect within both rural and metropolitan populations. Especially in metropolitan populations, the application of either type of distance-decay function is shown to be problematic by itself. Its inclusion necessitates the addition of a variable catchment size function which can enable the 2SFCA method to dynamically define more appropriate catchments which align with actual health service supply and utilisation.ConclusionThis study assesses recent ‘improvements’ to the 2SFCA when applied over large geographic regions of both large and small populations. Its findings demonstrate the necessary combination of both a distance-decay function and variable catchment size function in order for the 2SFCA to appropriately measure healthcare access across all geographical regions.

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.

The Geographic Profiling of Poverty and Accessibility: The Case of Two Provinces in the Philippines

This study attempts to relate the poverty problem in the Philippines using spatial accessibility measures. Spatial accessibility is the ease with which one could avail of the social services and economic opportunities laid in geographic space to the individual. Using the provinces of Eastern Samar and Siquijor Island as case studies, a Social Composite Index (SCI) value for the household was derived from the 13+1 CBMS core indicators of poverty, which represents the unmet needs of the household and which was then aggregated at the barangay level. The spatial accessibility values were estimated by measuring how each barangay, specifically households, would avail themselves of the social services (such as schools and hospitals) and economic opportunities in the town center or major economic centers. The ease or difficulty of availing these social services and economic opportunities was estimated using the time variable in order to relate accessibility to the poverty indicators in the barangay. Multiple regression models were developed to relate poverty indicators to spatial accessibility measures and then tested to determine their impact on poverty. The tests showed that expected improvements in accessibility of more elementary schools in Siquijor would redound to a higher SCI or lower poverty levels. The planned merger of hospitals in Eastern Samar, revealed a lower SCI or an increase in poverty levels. Clearly, therefore, the link between poverty and accessibility could be established using CBMS data, and more importantly, could be used to predict the impact of planned social infrastructures on poverty levels. Key Words: poverty; spatial accessibility; barangays; social composite index DOI: 10.3860/ber.v20i2.1913 DLSU Business & Economics Review 20.2 (2011), pp. 45-65

Spatial accessibility and availability measures and statistical properties in the food environment

Spatial accessibility is of increasing interest in the health sciences. This paper addresses the statistical use of spatial accessibility and availability indices. These measures are evaluated via an extensive simulation based on cluster models for local food outlet density. We derived Monte Carlo critical values for several statistical tests based on the indices. In particular we are interested in the ability to make inferential comparisons between different study areas where indices of accessibility and availability are to be calculated. We derive tests of mean difference as well as tests for differences in Moran’s I for spatial correlation for each of the accessibility and availability indices. We also apply these new statistical tests to a data example based on two counties in South Carolina for various accessibility and availability measures calculated for food outlets, stores, and restaurants.