With the diversification of train and railway technologies, rail transit systems are becoming increasingly varied. They are widely used not only in long distance land transportation but also in medium and short distance urban public transit. Common types include traditional railways (ordinary railways, intercity railways, and suburban railways), subways, light rails, and trams, as well as new systems such as maglev and monorail.
According to the Chinese national standard Terminology Commonly Used in Urban Public Transportation, urban rail transit is defined as “a general term for rapid, high-capacity public transportation that typically uses electric power and operates on wheel-rail systems.”Based on service scope, rail transit is generally divided into three categories: national railway systems, intercity rail transit, and urban rail transit.