Public transport (also known as public transportation, public transit, or mass transit) is a shared passenger-transport service which is available for use by the general public, as distinct from modes such as taxicab, carpooling, hired buses, and transportation network companies, which are not shared by the general public without private arrangement.
Public transport modes include city buses, trolleybuses, trams (or light rail) and passenger trains, rapid transit (metro/subway/underground, etc.) and ferries. Public transport between cities is dominated by airlines, coaches, and intercity rail. High-speed rail networks are being developed in many parts of the world. Most public transport systems run along fixed routes with set embarkation/disembarkation points to a prearranged timetable, with the most frequent services running to a headway (e.g.: “every 5 minutes” as opposed to being scheduled for any specific time of the day). Share taxis offer on-demand services in many parts of the world, and some services will wait until the vehicle is full before it departs. Paratransit is sometimes used in areas of low demand and for people who need a door-to-door service.
Urban public transit differs distinctly among Asia, North America, and Europe. In Asia, profit-driven, privately-owned and publicly traded mass transit and real estate conglomerates predominantly operate public transit systems  In North America, municipal transit authorities most commonly run mass transit operations. In Europe, both state-owned and private companies predominantly operate mass transit systems, Public transport services can be profit-driven by use of pay-by-the-distance fares or funded by government subsidies in which flat rate fares are charged to each passenger. Services can be fully profitable through high usership numbers and high farebox recovery ratios, or can be regulated and possibly subsidised from local or national tax revenue. Fully subsidised, free of charge services operate in some towns and cities.
For geographical, historical and economic reasons, differences exist internationally regarding use and extent of public transport. While countries in the Old World tend to have extensive and frequent systems serving their old and dense cities, many cities of the New World have more sprawl and much less comprehensive public transport. The International Association of Public Transport (UITP) is the international network for public transport authorities and operators, policy decision-makers, scientific institutes and the public transport supply and service industry. It has 3,400 members from 92 countries.