Geographic access modelling: AccessMod tool

Geographic access (or physical access) can be defined as how easily a population can physically access the health services that it needs. Although physical barriers can be very significant in certain regions, it is important to remember that there are other factors that can also restrict (or facilitate) access to health care, especially the existence (or absence) of financial and cultural barriers.

It is important to have a realistic model of geographic access to a network of health facilities in order to understand the extent to which the population is covered and to highlight the areas and parts of the population that are inadequately served. An access model is also needed for modelling the journey time between locations, particularly for referrals between facilities in the event of birth complications, for example.

A key concept in access modelling is the catchment area around a health facility. In theory, the population living in this area has physical access to the facility. Many studies and analyses use either a circular catchment area (e.g. with a radius of five kilometres) or an area corresponding to the administrative boundaries of a health district that the facility is supposed to cover with its services. These approaches can lead to errors or to significant under- or over-estimations regarding the extent of the population that actually has physical access to the facility within a given period of time. As illustrated in the figure 35 below, the shape and size of a catchment area are defined by using parameters related to factors restricting travel (e.g. mountainous areas, forests, rivers, impassable areas), facilitating it (e.g. road network), and means of transport (e.g. by foot and/or motorized vehicle) using a maximum journey time (e.g. two hours)²⁶. They can vary greatly from a circular catchment area defined.

It is therefore preferable to use the approach based on journey time, rather than distance, to obtain a realistic estimate as to what percentage of the population, in theory, has physical access to the network of EmONC facilities.

FIGURE 35: DIFFERENT MODELS OF CATCHMENT AREAS AROUND A HEALTH FACILITY (BLACK DOT)

LEGEND

A) Circle indicating a given distance, B) Consideration of aspects restricting patient travel (roads, forests, obstacles, mountains, etc.) indicating a more realistic area within a given maximum journey time, C) Additional consideration of the direction of travel (towards of or from a health facility) by which the speed of travel when walking or bicycling can change depending on the slope of the terrain.

AccessMod^xix (version 5) can generate a realistic model of physical access to healthcare by taking into account population distribution, availability of services and travel constraints. It is a free, open-source software that has been initially developed by WHO in 2005, and is currently maintained by the GeoHealth group - Institute of Global Health of the University of Geneva^xx, in collaboration with the Health GeoLab Collaborative.^xxi Packaged in a virtual machine, Accessmod can operate on various platforms (Windows, Linux, Mac) and be used in conjunction with any GIS application (e.g. QGIS, ESRI ArcGIS, etc.).

AccessMod comprises five key functions that enable it to obtain the following results:

• Accessibility analysis: models physical access to health facilities, i.e. the possibility that a target population can reach the nearest health facility within a given time (taking into consideration travel scenarios that may combine walking, cycling or motorized vehicles, at user-defined travel speeds, and also physical aspects that may restrict travel, such as rivers, forests, mountains, roads, hard-to-access areas, etc.).

• Geographic coverage analysis: models access while also taking into account the availability of services (or the health facility’s capacity to provide care, for example, in terms of number of beds, number of qualified staff, etc.). The result pinpoints the location of the population that can both get to the closest health facility within a

xix  Software download, user guide and tutorial are available at: http://accessmod.org xx  GeoHealth group / Institute of Global Health - http://www.unige.ch/geohealth

given maximum time (e.g. two hours) and can also be treated in that facility based on its capacity.

• Zonal statistics: provides the percentage of the population that has access to the network of health facilities within a given maximum journey time. These percentages can also be obtained for any administrative sub-unit.

• Referral analysis: calculates journey time and distance between different types of health facilities (e.g. between BEmONC and CEmONC facilities).

• Scaling-up scenarios: Identifies the optimum locations for new health facilities in order to maximize the population coverage of the scaled-up network, based on a user-defined prioritization model.

FIGURE 36: VARIOUS RESULTS OF MODELLING PHYSICAL ACCESS, OBTAINED USING ACCESSMOD: A) BURKINA FASO B) REGION IN TOGO C) MALAWI^27,28,29

C.

A.

B.

Travel time to

nearest EmONC facility

< 1 hour 1–2 hours 2–3 hours 3–4 hours

> 4 hours

Legend

BEmOC, including CEmOC (Ministry of Health) District boundaries (Census 2008)

Water bodies

Less than 1 hour travel time More than 1 hour travel time

It is important to note that AccessMod needs certain geospatial data sets for the modelling exercise. These are summarized in Figure 37.

FIGURE 37: GEOSPATIAL DATA ENTERED INTO ACCESSMOD TO MODEL PHYSICAL ACCESS, GEOGRAPHIC COVERAGE, AND REFERRAL.

Coordinates

of facilities Population

distribution Road

network Admin.

boundaries Rivers Land cover Elevations

AccessMod has already been used in about 20 countries and is generating increasing interest, particularly in Africa and Asia. Not only are the advantages of using it linked to improvements in access to health services, but also to improvements in the quality of geographic data sets and the ability of stakeholders to use GIS and conduct analysis beyond the basic thematic map. Using AccessMod also contributes to implementing SDGs 3.7 and 3.8, and the service coverage indicators that form part of a global reference list of 100 core health indicators set out by WHO.³⁰

3.3 GIS and AccessMod – applications to support the development of the national network