The approaches to measuring the potential spatial access to urban health services revisited: distance types and aggregation-error issues

Abstract

BackgroundThe potential spatial access to urban health services is an important issue in health geography, spatial epidemiology and public health. Computing geographical accessibility measures for residential areas (e.g. census tracts) depends on a type of distance, a method of aggregation, and a measure of accessibility. The aim of this paper is to compare discrepancies in results for the geographical accessibility of health services computed using six distance types (Euclidean and Manhattan distances; shortest network time on foot, by bicycle, by public transit, and by car), four aggregation methods, and fourteen accessibility measures.MethodsTo explore variations in results according to the six types of distance and the aggregation methods, correlation analyses are performed. To measure how the assessment of potential spatial access varies according to three parameters (type of distance, aggregation method, and accessibility measure), sensitivity analysis (SA) and uncertainty analysis (UA) are conducted.ResultsFirst, independently of the type of distance used except for shortest network time by public transit, the results are globally similar (correlation >0.90). However, important local variations in correlation between Cartesian and the four shortest network time distances are observed, notably in suburban areas where Cartesian distances are less precise. Second, the choice of the aggregation method is also important: compared with the most accurate aggregation method, accessibility measures computed from census tract centroids, though not inaccurate, yield important measurement errors for 10% of census tracts. Third, the SA results show that the evaluation of potential geographic access may vary a great deal depending on the accessibility measure and, to a lesser degree, the type of distance and aggregation method. Fourth, the UA results clearly indicate areas of strong uncertainty in suburban areas, whereas central neighbourhoods show lower levels of uncertainty.ConclusionIn order to accurately assess potential geographic access to health services in urban areas, it is particularly important to choose a precise type of distance and aggregation method. Then, depending on the research objectives, the choices of the type of network distance (according to the mode of transportation) and of a number of accessibility measures should be carefully considered and adequately justified.

Cross-border spatial accessibility of health care in the North-East Department of Haiti

“…Thus, the opening of the border only impacts spatial accessibility for the Haitian population in the vicinity (travel time zones 0–15 min and 15–30 min). These results are not surprising, as these areas have a road network in good condition, confirming the importance of a good road network [4, 82–84] and of the type of distance [78] in potential spatial accessibility. As a result, rural areas are those with the lowest level of accessibility, on the one hand, and, on the other hand, these areas benefit very little from the opening of the border, despite its proximity.…”

“…Geographic constraints as well as road conditions can trigger low access to health care and impact the use of health care facilities, with important repercussions for health outcomes and public health. Several methods are used to measure spatial accessibility [77, 78]. The approach based on available supply assumes that all users within the same catchment area have equal access regardless of the geographic constraints [9, 77].…”

Exploring spatiotemporal variations in public library provision following a prolonged period of economic austerity: A GIS approach

“…Population counts from the 2011 UK census and 2017 mid‐year estimates, both sourced from ONS, were used for the 2011 and 2018 accessibility calculations respectively. The limitations of using the centroid of census tracts to represent the origin of potential demand for services has been recognised (Apparicio et al., ), and while the use of population weighted centroids address some of these concerns (especially for large rural LSOAs), it is nevertheless acknowledged that their application in network‐based models may not necessarily reflect the actual time taken to access library facilities from all residential locations. In addition, the models assume that travel is via private transport only, due to a lack of openly accessible data on public transport routes and timetables at the all‐Wales level.…”

L'identification des zones calmes et un diagnostic d’équité environnementale à Montréal

“…Il s'agit plus spécifiquement d'une distance exprimée en minute de marche, représentant le temps de déplacement d'un piéton. Pour modéliser ce temps de déplacement, nous utilisons la fonction de Tobler prenant en compte la pente de chaque segment (Apparicio et al ).…”

“…Parmi les mesures d'accessibilité les plus couramment utilisées dans les études d'accessibilité (Talen et Anselin , Apparicio et al ) nous avons retenu la distance à la zone calme la plus proche. Cette mesure permet d'évaluer la proximité immédiate aux zones calmes, à savoir la distance minimale à parcourir (en minutes) du centroïde de l'AD à la zone calme (ZC) la plus proche à travers le réseau de rues.…”