The Lamu Port–South Sudan–Ethiopia Transport (LAPSSET) Corridor is sub-Saharan Africa's largest infrastructure development programme, encompassing a 1,700 km standard-gauge railway, 1,900 km of highway, a deep-water port at Lamu, three resort cities, and an oil pipeline connecting the South Sudan oilfields to the Indian Ocean coast. With an estimated total investment exceeding USD 24.5 billion, the LAPSSET corridor is projected to transform the trade geography of the Horn of Africa by providing Kenya, South Sudan, and Ethiopia with a shorter, lower-cost alternative to the Northern Corridor (Mombasa–Nairobi–Kampala) and to the Djibouti–Addis Ababa corridor. This study presents a comprehensive network analysis of the LAPSSET corridor using graph-theoretic methods, spatial network modelling in GIS, and four-stage transport demand modelling to quantify the connectivity and trade facilitation impacts of the corridor under three completion scenarios. A weighted directed graph G (V, E) with 32 nodes and 68 edges was constructed to represent the LAPSSET and connecting national road networks. Centrality metrics betweenness, closeness, eigenvector, and Bonacich power centrality were computed for all nodes to identify critical connectivity hubs and potential vulnerability points. Shortest-path and travel-time accessibility indices were derived for 96 origin–destination pairs. The study finds that full LAPSSET completion would reduce mean travel time between Lamu and Juba from 52 hours to 18 hours, lower heavy truck vehicle operating costs by an average of 34% on the Isiolo–Moyale segment, and increase the weighted accessibility index of the eight most transport-deprived counties by 62–82%. The LAPSSET corridor is projected to generate USD 3.2–4.8 billion per year in incremental tr