A harmonised framework for assessing geographic healthcare access across the rural-urban continuum

Abstract Background Equitable access to healthcare is essential for sustainable development, yet spatial inequalities are often assessed using inconsistent definitions for classifying the rural-urban continuum. We aimed to develop a harmonised framework to assess geographic healthcare access across the rural–urban continuum using comparable metrics. We apply this framework to Nigeria and Zambia as contrasting case studies, reflecting differences in population size, settlement patterns, and levels of urbanisation. Methods We combined high-resolution population data with geolocated healthcare facilities and modelled travel times to the nearest facility using walking and motorised transport scenarios at 1-km resolution. Settlement types were classified using the Degree of Urbanisation method, a globally standardised approach that categorises areas into cities, towns and semi-dense areas, and rural areas based on population density and settlement size. We analysed travel-time distributions and relative accessibility using a comparative metric across settlement types. Results Here we show that 90% of the population in Nigeria and 80% in Zambia can reach any healthcare facility within 15 minutes by motorised transport, compared with 60% and 54%, respectively, on foot. For hospitals, only 61% (Nigeria) and 47% (Zambia) are within 15 minutes by motorised transport, and 8% in Nigeria by walking. In Nigeria, 45% of the population remain more than 120 minutes from hospitals on foot, compared with 54% in Zambia. Across both countries, cities generally have better access, but substantial overlap exists, with some urban populations (defined as the share of population living in cities, towns and semi-dense areas) experiencing travel times comparable to and even worse than rural populations. Uncertainty arises from assumptions in travel speeds and input datasets, but relative patterns are consistent across scenarios. Conclusions These findings indicate that geographic healthcare inequalities extend beyond a simple rural–urban divide and include underserved populations within cities, towns and semi-dense areas. A harmonised framework based on consistent settlement definitions can support more comparable and policy-relevant assessments of healthcare access across countries and inform targeted infrastructure and service planning.