The opposite phrase heavy rail, used for higher-capacity, higher-speed systems, also avoids some incompatibilities in terminology between British and American English, as for instance in comparing the London Underground and the New York City Subway.
Conventional rail technologies including high-speed, freight, commuter, and rapid transit urban transit systems are considered "heavy rail".
The main difference between light rail and heavy rail rapid transit is the ability for a light rail vehicle to operate in mixed traffic if the routing requires it.[19]