Urban public transport in Ouagadougou faces several challenges, one of which is the use of butane gas as fuel by certain informal taxis. This research aims to analyse the dynamics of the adoption of this practice and its determining factors. The methodological approach combines documentary research, direct observation in the field, quantitative surveys of drivers, households and customers, and semi-structured interviews with key stakeholders. The data collected has made it possible to establish an overview of the phenomenon. The results show that while the use of butane gas remains marginal (25% of taxis), it is growing, driven by rising traditional fuel prices, subsidised gas availability, and the search for profitability. However, this practice is hampered by technical and regulatory constraints and negative perceptions related to accident risks. Social normalisation and weak administrative control contribute to its persistence. Understanding these factors is essential for developing effective policies that guarantee the safety and sustainability of urban mobility.