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.
Balloon loops are common on
tram and streetcar systems. Many streetcar and tram systems use single-ended vehicles that have doors on only one side and controls at only one end. These systems may also haul trailers with no controls in the rear car, and, as such, must be turned at each end of the route.
History
Balloon loops were first introduced on
tram
A tram (also known as a streetcar or trolley in Canada and the United States) is an urban rail transit in which Rolling stock, vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some ...
and, later,
metro lines. They did not commonly appear on freight railways until the 1960s, when the modernising
British Rail
British Railways (BR), which from 1965 traded as British Rail, was a state-owned company that operated most rail transport in Great Britain from 1948 to 1997. Originally a trading brand of the Railway Executive of the British Transport Comm ...
system introduced ''
merry-go-round'' (MGR) coal trains that operated from mines to power stations and back again without
shunting.
Tramways
On the former
Sydney
Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...
tram system, loops were used from 1881 until the second-generation system's closure in 1961. Initially, the Sydney system was operated by single-ended
steam trams; then from the 1890s by double-ended electric trams. Lines were looped in the Sydney CBD and the other busiest areas of operation, such as the eastern suburbs lines, as they provided greater turn-around capacity on the crowded system. The Sydney system was the first example of a tramway system using loops and has continued to build them up to 1997 (third-generation system).
Later in the 19th century, looped streetcar (tram) lines also began to appear on systems in the US, and soon looped operation with single-ended streetcars became widely used on many North American streetcar systems. European systems were almost universally converted to looped operation in the early 20th century, and most also adopted single-ended trams. Loops were also used on some tramways in Asia, South America and New Zealand, as well as on other Australian systems in addition to Sydney. Looped operation with single-ended trams is still the predominant method of tramway operation in the world, in spite of the recent construction of some new, typically smaller, stubbed systems with double-ended trams.
Usage
Balloon loops are used extensively on
tram
A tram (also known as a streetcar or trolley in Canada and the United States) is an urban rail transit in which Rolling stock, vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some ...
way systems with single-ended trams. Usually located at termini, the loop may be a single one-way track round a block. Single-ended trams have a cab at only one end and doors on one side, making them cheaper and having more space for passengers. On tram systems with double-ended trams balloon loops are not required but may still be used as they can provide greater turn-around capacity than a stub terminus.
Balloon loops enable higher line capacity (faster turnaround of a larger number of trams) and allow the use of single-ended trams which have several advantages, including lower cost and more seating. However, double-ended trams also benefit from the capacity advantage of balloon loops.
Occasionally, balloon loops are used for reversing trains on lines with heavy grades and tight curves to equalize wear on both sides of locomotives and rollingstock. Such a balloon loop was constructed at Beech Forest on the Victorian Railways line from Colac to Crowes.
Efficiency and convenience of operation
* Trains can arrive and leave simultaneously, as long as an open platform exists.
* Time is not lost while drivers change ends and reset the train for the other direction.
* Eliminates the need for brake test if locomotives uncoupled to carry out run around the move.
Infrastructure optimisation
* Fewer tracks and platforms are required.
* Arrivals into some platforms do not block departures from other platforms.
Train maintenance and durability
* Reversal allows even wear and tear on the wheels.
Spatial and structural constraints
* Very space-consuming.
* If the driver changed ends and discovers a hidden fault, delays are less likely.
Track and train adaptability
* The sharp curves cause noise, as well as wear on wheels and rails.
* Due to the presence of sharp curves in balloon loops, heavy haul trains are required to operate at reduced speeds to ensure safe and efficient movement.
* On systems, where, for reasons of economy, the couplings are made non-reversible (e.g. by fitting the air brake pipe along one side of the car only), the use of a balloon loop will cause a proportion of the rolling stock to face the "wrong" way and it may not be possible to assemble a complete train in a depot, even if sufficient cars are on hand.
Solutions

* On many systems with a balloon loop, the couplings and brake hoses are made reversible.
* At coal ports such as
Kooragang in
Newcastle, New South Wales
Newcastle, also commonly referred to as Greater Newcastle ( ; ), is a large Metropolitan area, metropolitan area and the second-most-populous such area of New South Wales, Australia. It includes the cities of City of Newcastle, Newcastle and Ci ...
the space inside the balloon loops is used for storing coal so that it is not wasted.
* At the
Olympic Park station in
Sydney Olympic Park
Sydney Olympic Park is a suburb of Greater Western Sydney, located 13 kilometres west of the Sydney central business district, in the Local government in Australia, local government area of the City of Parramatta, City of Parramatta Council. It i ...
, the loop is flattened where the platforms are located, so that the platform faces are straight.
* After the opening of a loop at
Charing Cross (Embankment) in 1914 (replaced in 1926 by the present
Kennington loop) car ends were marked "A" or "B" (later, when axles were designated by letters, the "B" car ends became "D" to match the adjacent axle), and it was not permitted to couple cars together if the ends to be coupled bore the same letter. It was found necessary to provide a
turntable
A phonograph, later called a gramophone, and since the 1940s a record player, or more recently a turntable, is a device for the mechanical and analogue reproduction of sound. The sound vibration waveforms are recorded as corresponding phys ...
at
Golders Green depot (near the other end of the line), for use when there was an imbalance of car directions.
* The former
South Ferry station on the
New York City Subway
The New York City Subway is a rapid transit system in New York City serving the New York City boroughs, boroughs of Manhattan, Brooklyn, Queens, and the Bronx. It is owned by the government of New York City and leased to the New York City Tr ...
solved the railcar door hazard by using
gap fillers that extended out to the railcar door when the train triggered a switch on the tracks. The older station was closed in 2009, but was reopened between 2013 and 2017 as a result of damage to the newer station caused by
Hurricane Sandy
Hurricane Sandy (unofficially referred to as Superstorm Sandy) was an extremely large and devastating tropical cyclone which ravaged the Caribbean and the coastal Mid-Atlantic (United States), Mid-Atlantic region of the United States in late ...
.
References
External links
*
{{Rail tracks
Railway track layouts
Tram loops