Most large-scale urban bike sharing programmes utilise numerous bike check-out stations, and operate much like public transit systems, catering to tourists and visitors as well as local residents. Their central concept is to provide free or affordable access to bicycles for short-distance trips in an urban area as an alternative to motorised public transport or private vehicles, thereby reducing congestion, noise, and air pollution. Bicycle-sharing systems have also been cited as a way to solve the "last mile" problem and connect users to public transit networks.