Urban expansion and differential accessibility by car and public transport in the Greater Kumasi City-region, Ghana—a geospatial modelling approach

There is a growing recognition of the worsening problems of accessibility in Africa’s major urban centres and city-regions. Yet, research assessing differential accessibility in these contexts is limited, partly because of the lack of population and land-use data at granular spatial resolutions. In this paper, we contribute to addressing the existing challenges by presenting a geospatial modelling approach that combines historical urban physical development data extracted from Landsat satellite images, travel time data from Openrouteservice and Google Maps API services, and relevant transport infrastructure data. We apply the approach to analyse place-based (100 m2) accessibility in the Greater Kumasi city-region of Ghana. The analysis reveals a strong co-evolutionary relationship between physical development and geographical accessibility, with an estimated 83% of the emergent physical development located within half-a-kilometre distance of a primary road. First-and-last-mile accessibility in terms of walking time to public transport stations and public transport service routes are quantified. We reveal huge first-and-last-mile accessibility deficits, with an estimated 14% and 33% of the city-region’s built-up area having a 5-minute and 10-minute walking time reachability to a public transport station, as a critical node of accessibility. Differential accessibility by car and public transport is analysed, focusing on the city-region’s most important functional centre (i.e. CBD). The results show that the CBD is within 15 minutes and nearly 30 minutes reach by car and public transport respectively, for only 1% of the city-region’s built-up area. This implies that overall accessibility is poor regardless of mode choice, due to congestion. The findings underscore the need for integrative urban development and accessibility planning in the city-region.