Rural road connectivity is widely regarded as a prerequisite for sustainable rural development, yet rigorous causal evidence on the magnitude and distribution of road connectivity impacts on household livelihoods in post conflict Sub Saharan African contexts remains limited. This paper presents a comprehensive socio economic impact assessment of rural road improvement in Central Equatoria State, South Sudan, combining a Difference in Differences (DID) quasi experimental design, instrumental variable (IV) regression, and mixed methods household survey data to estimate the causal effect of road connectivity on livelihood outcomes. A panel dataset of 714 households in 18 treatment villages (which received rural road rehabilitation between 2019 and 2022 under the World Bank funded South Sudan Rural Roads Project) and 16 matched control villages was assembled through four survey rounds (2018–2024). Primary outcomes measured include: household monthly income, food security index, school attendance rates, health facility utilisation, agricultural productivity, and women's economic empowerment index. The DID estimator identifies an Average Treatment Effect on the Treated (ATT) of USD 108 per household per month in income (95% CI: USD 84–132), a 0.8 point improvement in food security (p < 0.001), a 16.4 percentage point increase in school attendance, and a 26.2 percentage point increase in health facility utilisation. Heterogeneity analysis reveals that smallholder farmers and non farm entrepreneurs experience the largest income gains (ATT = USD 138 and USD 162 respectively), while elderly headed and pastoral households benefit significantly less (ATT = USD 58 and USD 44), highlighting the distributional equity dimensions of road investment. An IV analysis using road gradient as