The trails of all-terrain motorcycles!
The term trail is used to refer to races in the wilderness and also to all-terrain motorcycles.
Trails were marketed with single-cylinder engines, then the BMW GS created the twin-cylinder engine in 1980, giving a larger displacement without the disadvantages linked to single-cylinder engines (fast wear at high rpm, vibrations). The idea was successful and nowadays all the large displacement trailers use a twin-cylinder engine, or even a three- and four-cylinder engine.