Urban policy makers are increasingly interested in cycling as part of a sustainable and reliable transport network. One of the ways through which cities promote cycling is by providing a public bicycle system (PBS). This paper studies demand for public rental bicycles following local and temporary metro interruptions in Paris. We construct a unique data set by linking metro interruptions announced in Twitter communication by the Parisian metro operator to usage data on the Vélib’ PBS. We find that, as a direct consequence of a metro interruption, the consumption of bicycles within 100 metres of metro stations increases by 0.72 bicycles per hour on average, and with 1.54 bicycles per hour during the first 20 minutes; an increase of approximately 11% and 22% respectively. Due to their effects on demand, metro interruptions increase the probability of empty stocks at rental stations with 15%. Back-of-the-envelope calculations indicate that the presence of the PBS in Paris reduces welfare losses from metro interruptions by 2.1 million euros per year. The findings highlight that cycling is a local net substitute for metro service, and that public rental bicycles can alleviate welfare losses stemming from public transport interruptions.