According to Nice classification heading for class 12 states Vehicles; Apparatus for locomotion by land, air or water are included in Class12 The heading gives you a brief broad overview about what exactly is including in a particular class.
This Class includes, in particular: – motors and engines for land vehicles; – couplings and transmission components for land vehicles; – air cushion vehicles. This Class does not include, in particular: – certain parts of vehicles (consult the Alphabetical List of Goods); – railway material of metal (Cl. 6); – motors, engines, couplings and transmission components other than for land vehicles (Cl. 7); – parts of motors and engines (of all kinds) (Cl. 7).