Using data from two case cities (Zomba and Kakamega), this paper examines mobility poverty through the lens of mobility security, a framework inspired by two social development frameworks: food security and market systems. The mobility security concept offers a framework for identifying challenges and developing intervention pathways specific to bicycle access and use.  Recent research has aligned definitions for mobility/transportation poverty, introduced indicators, devised population estimation methods, and proposed equity principles; however, there does not yet exist a systems change framework for assessing a minimum state of mobility or access for individuals’ needs to be met. Therefore, this paper proposes a concept of ‘mobility security’ and presents a framework to assess it. This framework was developed by reviewing the literature on transportation/mobility poverty, equity, and select social development frameworks.  The food security and market systems frameworks emerged as the most appropriate to adapt to the transport sector.  Using an individual/group’s desired mode of transportation as a starting point, the framework considers the mode's availability (supply), user access, use (capacity/demand), and the resultant positive and negative outcomes. The new framework was then piloted to analyse bicycle mobility data collected from marginalized groups in the two case cities. The mobility security framework presented a useful way to organize the data by geography and transport mode and identify program and/or policy areas to focus on and prioritize within the pillars of availability, access, and use. This paper is an extension of a broader research study, funded by the Volvo Education and Research Foundation, that investigates the role of the bicycle in mitigating mobility poverty in Kenya and Malawi.