Uni-directional Vehicle

A uni-directional vehicle is a

vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles ( motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles ( trains, trams ...

that is normally designed to operate only in the forward direction. While the vast majority of

road vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles ( trains, trams), ...

s are like this, the term generally refers to a

train In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often k ...

tram A tram (called a streetcar or trolley in North America) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport ...

with a distinguishable front and rear end and a single operating cab at the front end. These vehicles often have the capability to operate in reverse, though such operations are limited to low speeds and short distances, such as shunting. Uni-directional vehicles commonly have entry and exit

door A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a ''doorway'' or ''portal''. A door's essential and primary purpose is to provide security b ...

s on only one side of the vehicle (usually the

sidewalk A sidewalk (North American English), pavement (British English), footpath in Australia, India, New Zealand and Ireland, or footway, is a path along the side of a street, highway, terminals. Usually constructed of concrete, pavers, brick, stone ...

side), although some are equipped with doors on both sides, or operate in opposing traffic flow, to facilitate the use of

island platform An island platform (also center platform, centre platform) is a station layout arrangement where a single platform is positioned between two tracks within a railway station, tram stop or transitway interchange. Island platforms are popular ...

s. Having doors on only one side allows for an increase in seating on board the vehicle, compared to

bi-directional vehicle A bi-directional vehicle is a vehicle that can be driven in either direction, forwards or backwards. Usually, the term refers to rail vehicles, such as trains or trams, and some airside transfer buses, that are equipped with driver's cabs ...

s which have doors on both sides. Because a uni-directional vehicle can only travel in one direction they require special infrastructure for turning around at a

terminal station A train station, railway station, railroad station or depot is a railway facility where trains stop to load or unload passengers, freight or both. It generally consists of at least one platform, one track and a station building providing ...

. This is usually a

balloon loop A balloon loop, turning loop, or reversing loop ( North American Terminology) allows a rail vehicle or train to reverse direction without having to shunt or stop. Balloon loops can be useful for passenger trains and unit freight trains. Bal ...

on tram systems, which mainline railways tend to use a triangle junction or

turntable A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

. Tram vehicles Rail transport {{rail-transport-stub