Ile-de-France Mobilités, the regional transport authority of the Île-de-France region in France, has ambitious goals for the decarbonisation of its fleet, which includes buses, trams, suburban trains (RER), metro trains and other means of transport. By 2025, they aim to make buses 100% sustainable in the most densely populated area, extending this target to all vehicles operated in the region by 2030. But how do you choose between different sustainable transport options? The decision is mainly oriented between electric and biomethane transport. This last option is undoubtedly the most convenient, ready to use and offers superior performance in terms of autonomy.