Introduction: Urban growth in Africa is increasing mobility demand, with high-volume transport infrastructure developed to cope with stress on existing infrastructure. Such infrastructure development often entails risk accumulation (i.e. the potential build-up of vulnerabilities, hazard and negative externalities), and associated impacts on adjacent communities. This paper investigates how high-volume transport road infrastructure impacts the resilience, environment, and well-being of communities during the construction phase, including reactions/adaptations to the development of such projects. The paper uses the case study of the Missing Link #12 bypass in Nairobi, Kenya, where the development passes through the informal settlement of Kibera. Methods: The study uses an explanatory sequential mixed-method approach to explore the wider socio-economic, transport, and environmental impacts during the construction of the Missing Link #12 on the community of Kibera. Data collection comprises a survey with 452 households, six focus groups and a community engagement workshop. Results: The Missing Link #12 has had a divisive socio-economic effect on Kibera's community, due to spatial relocations, loss in livelihood, and breakdown in community social cohesion and interaction. While under construction, the road was not physically closed, but used by residents as non-motorized transport infrastructure, leading to increased walking and improved access to popular transport options. Health concerns linked with environmental risks of increased exposure and vulnerability to air and noise pollution emerged strongly, together with road safety issues caused by the shared environment with motorized transport modes. Conclusions: The case study shows the importance of accounting for risk accumulation for road-building infrastructure projects, starting from construction stage. Infrastructure development in African cities must be more inclusive and take into account the impacts on local communities, with success measured beyond the goal of reducing traffic congestion for car-owners. This is particularly true where more vulnerable and disenfranchised populations like in informal settlements are affected.