Rapid transit is a type of high-capacity, urban public transportation that operates on an exclusive right of way that cannot be accessed by pedestrians and road vehicles and thus allows relatively high speeds. The right of way can be in tunnels, on elevated structures, or on the surface, and it is usually some combination of these. Tunnels are the most common type of right of way in city centers and thus rapid transit systems are often referred to as "subways."
The vehicles on most true rapid transit systems have steel wheels that operate on steel rails, similar to a conventional railroad, and nearly all such systems are powered by electricity that is obtained through a third rail or overhead wires.