A harmonised framework for assessing geographic healthcare access across the rural-urban continuum: case studies from Nigeria and Zambia

Equitable access to healthcare is essential for achieving sustainable development, yet the spatial dimensions of disparities remain poorly understood across the full rural–urban continuum. This study proposes a general, harmonised framework that integrates the UN-endorsed Degree of Urbanisation method with travel-times to identify and compare patterns of geographic healthcare access in Nigeria and Zambia. We estimated travel times to any healthcare facility and hospitals for both walking and motorised transport at 1-km spatial resolution, and analysed disparities across cities, towns and semi-dense areas, and rural areas. Results reveal strong positive rural–urban gradients in geographic healthcare access across both countries, but also substantial overlap between different settlement classes, indicating that poor geographic access to healthcare facilities is not limited to rural areas alone. In Nigeria, accessibility deficits are also observed in city-fringe zones, whereas in Zambia, the main constraint remains the rural isolation outside the well-connected Lusaka–Copperbelt corridor. These findings highlight the importance of 1) adopting a multi-scale, spatially disaggregated planning, 2) improving rural connectivity through road and referral-facility investments, and 3) enhancing urban and peri-urban healthcare access through the integration of transport infrastructure and facility location planning. The proposed framework enables consistent cross-country assessment of geographic healthcare access and can be extended to other essential services for supporting the progress toward the Sustainable Development Goals.