Bicycle carrier
A bicycle carrier, also commonly called a bike rack, is a device attached to an automobile or bus for transporting bicycles. By vehicle type. Bus mounted bike carriers are usually attached to the front of the bus. They may flip up against the bus, out of the way, when not carrying any bikes. Automobile mounted bike carriers can be attached to the roof, rear trunk, or rear tow hitch, depending on the vehicle. Bikes may be mounted in the carriers by clamping both wheels and providing some additional vertical support, by clamping the rear wheel and the front  dropouts (necessitating the removal of the front wheel, which may be mounted separately on blades), or by clamping the top tube (usually in the case of rear hitch mounted carriers). There is a device available that connects from the stem to the seat post, to provide a top tube equivalent suitable for mounting in these carriers for step-through frame bicycles that do not have a top tube. Carriers that clamp on the front dropouts may also provide a built-in locking mechanism. Carriers have been developed especially for the rear of pickup trucks that attach either to the bed  or its sides. Special long carriers have been developed to support long-wheelbase recumbents and tandems. At least one manufacturer offers bicycle carriers for use on motorcycles. Children's bikes with wheels smaller than 16" may be too small for the racks on buses. Transit authorities with bicycle carriers on buses. Transit authorities with bicycle carriers on buses: