7.4 Location-allocation modelling

Location-allocation models are used to identify the optimal locations for new facilities, such as a new site for a birthing centre given the current available sites of care and underlying population demand. Other applications include provision of schools with consideration of local population characteristics. There are a few different considerations possible when creating a location-allocation model. For instance, do you want to ensure that the most people who need to access a service reach it easily, or is a priority to reach the facility most quickly (or using public vs. private transportation? These points must be addressed when planning the analysis.

Location-allocation models are a natural extension of the previous approaches considered in this section, catchment models and site availability/suitability using MCE.

Background to location-allocation models

The background to location-allocation models is in mathematical programming approaches, where mathematical programming can be described as “a set of numerical methods for solving optimization problems” (Cromley & McLafferty, 2012:349). Earlier applications of this approach to problem-solving the best location of a new service lies in business, and we now see it applied to public health scenarios. As well as planning new facilities, there is the ability to use location allocation models to assess service provision in an area.

Considerations

As with all spatial analyses, data quality (timeliness, completeness, spatial accuracy) will strongly influence the results of your model. There are further factors which must be noted in location-allocation models, such as the distance people are able to travel easily (and means of transport), the scale of administrative units used in the analysis and the priority of the particular model. The priority will depend on the task, but it may include examples like: maximize coverage or attendance, minimize impedance (such as travel cost). The target population is also crucial: when locating a new centre for dementia care, the target population will be quite different from a new maternity ward. A good understanding of the requirements for the target population and any particular challenges they may face will improve the results of your model.

Components of the model

Facility: this can be an existing site (required site) or a potential new site (candidate site).
– Each facility will have associated characteristics to aid the model calculations, such as Attractiveness (Weight). This might include the number of doctors at a certain level of experience at a facility, or the square footage of a retail outlet.
– For some location-allocation models there may be a parameter for Capacity. When it is reached, further demand will be allocated elsewhere.

Demand: these will be the points of origin, to represent patients or other users of a facility.

Distance cutoff: This will vary based on your demand, as noted above in Considerations.

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