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Balloon loop at Linnéplatsen at the tramway in Göteborg, Sweden.
Double sided island platform on a balloon loop - Olympic Park, Sydney, Australia
P1 & P4 departures
P2 & P3 arrivals

A balloon loop or turning loop allows a rail vehicle or train to reverse direction without having to shunt or even stop. Balloon loops can be useful for passenger trains and unit freight trains such as coal trains.

Balloon loops are common on tram or streetcar systems. Many streetcar and tram systems use single-ended vehicles that have doors on only one side and must be turned at each end of the route, or else haul trailer cars with no driver's cabin in the rear car.

History[edit]

Balloon loops were first introduced on metro and tram lines. They did not appear on freight railways in large numbers until the 1960s when the modernising British Rail introduced merry-go-round (MGR) coal trains that operated from mines to power stations and back again without shunting.

Tramways[edit]

Balloon loops are essential for operating single-ended trams. Balloon loops were also used in Sydney, especially for its steam trams; some loops were retained for double-ended electric trams, such as at La Perouse, New South Wales, as they provided greater turn-around capacity on this very busy system.

Examples[edit]

Passenger[edit]

South Ferry balloon loop

On a balloon loop: the station is on the balloon loop, and the platform may be curved or straight.

Australia[edit]

Canada[edit]

United States[edit]

Lower level (suburban) layout of the Grand Central Terminal, showing a balloon loop
Upper level (mainline) layout of the Grand Central Terminal, showing a balloon loop

United Kingdom[edit]

Other[edit]

  • Various stations of the Hong Kong Tramways
  • The Charleroi Pre-metro system features two balloon loops, at Beaux-Arts and Waterloo stations.
    In the Charleroi Pre-metro, both the Beaux-Arts and Waterloo stations have balloon loops. At Beaux-arts, trains between Sud and Anderlues (line 89, both directions) first run through the station on a platformless track, take the underground balloon loop then stop at the platform leading to their destination. Waterloo station services three lines (54, 55 and 88) going to three directions, on a single island platform. Trains from Gilly station either diverge to the right and end up at the station to continue to Parc station, or diverge to the left to end up on the other end of the island platform to go towards Beaux-Arts. At the station is also a bypass so trains can run from Gilly directly to Beaux-Arts, without halting at the platform. No scheduled trains thus fully run the loop (or the bypass).
  • The Amsterdam tram system has balloon loops at the end of all lines except for line 5 terminus at Amstelveen Binnenhof.[5] In front of Amsterdam Centraal, there are two balloon loops. One serves tram lines 1, 2, 5, 13 and 17 (west side) and the other (east side) serves trams 4, 9, 14, 16 and 26.[6] Across the city there are several disused balloon loops that were in use until lines were extended or abolished.

Multiple stations on a balloon loop:

  • Heathrow Terminal 4 and Terminals 1,2,3 stations on the Piccadilly line of London Underground.[7]
  • The LACMTA Blue Line has four stations on its loop through downtown Long Beach (California).
  • In Liverpool, England, on the Wirral Line of the Merseyrail network, trains arriving at Liverpool through the Mersey Tunnel fork left at Mann Island Junction onto a balloon loop, before reaching James Street (platform 1); they then call at deep-level platforms at Moorfields, Liverpool Lime Street and Liverpool Central before reaching James Street again (platform 3), then rejoin the original route at Mann Island Junction and then pass back through the Mersey tunnel.[8]
  • The City Loop or Melbourne Underground Rail Loop, Melbourne, Australia, has five stations. There a four loops, one from the north east and three from the south west, on two levels. The loops are bi-directional. A connection enables one of the south east loops to be used as a circle line. The are no connections between the four loops.
  • In the Helsinki area, the Kehärata or Ring Rail Line is being built between an existing branch at Vantaankoski and the main line at Tikkurila, primarily to serve the airport which is presently only accessible by road. It is expected to open in 2014. Two existing stopping services (to Tikkurila and Vantaankoski) will be replaced by a single service which traverses the whole loop and returns to Helsinki, stopping twice on opposite sides of Pasila station. Four new stations are planned, but the loop will have a total of 21 stations, not counting Pasila or Helsinki. Roughly half of these stations are on the northbound and westbound mainlines, the loop line leaving them via diving junctions at Hiekkaharju and Huopalahti.

With balloon loop: The balloon loop is past the station.

Brooklyn Bridge and City Hall stations in New York City.

Paris Métro[edit]

Tram Systems[edit]

Balloon loops are used extensively on tramway 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. The Milan interurban tramway network, although using double-ended trams, had balloon loops at termini within the city limits so that they could be used as backup termini by the single directional trams used on urban service. In Milan, tramway depots are built as balloon loops, just as urban termini. Another example is in Potsdam, Germany.

Freight[edit]

Australia[edit]

Queensland

Loading loops

New South Wales
  • Coal
    • Camberwell — Coal
    • Craven — Coal
    • Fassifern — Coal - has triangle as well, so trains can go north or south
    • Gunnedah — Coal
    • Mount Thorley — and other mines - coal
    • Newdell Junction — Coal - has two balloon loops for different coal mines
    • Newnes Junction coal loader
    • Tahmoor — Coal - due to change in operational requirements, the balloon loop now points the wrong way, and requires trains to be top and tailed.
    • Ulan — Coal
    • Wilpinyong — Coal
  • Wheat
    • Penny Road, near Moree — Wheat
South Australia

Unloading loops

New South Wales
  • Eraring - power station
  • Vales Point — power station ; Coal unloader
  • Port Waratah — Coal & Wheat unloader at port
  • Koorang Island — Coal unloader at port
  • Port Kembla - coal and wheat
South Australia
Victoria
West Australia
  • Yarrie — Iron ore [12]
  • Koolyanobbing — Iron Ore

Africa[edit]

Germany[edit]

New Zealand[edit]

United Kingdom[edit]

There are several balloon loops at power stations in the UK; these have been provided so that coal trains may unload without stopping (known as the merry-go-round system). Examples include Cottam, Didcot, Drax, Eggborough, Ferrybridge, and Ratcliffe-on-Soar.

Also, the Fife Circle line between Edinburgh and the county of Fife acts like a giant balloon loop, branching off after Inverkeithing and connecting again at Kirkcaldy.

United States[edit]

Other[edit]

Both the French and the British terminals of the Eurotunnel Shuttle service through the Channel Tunnel consist of balloon loops.

Occasionally, balloon loops are used for reversing trains on lines with heavy grades and tight curves to equalise wear on both sides of locomotives and rollingstock. Such a balloon loop was constructed at Beech Forest on the 2 ft 6 in (762 mm) Victorian Railways line from Colac to Crowes.

Advantages[edit]

Advantages of a balloon loop include:

  • Smooth operation
  • Trains can arrive in any free platform, while another train is leaving any platform.
  • Reversal of rolling stock helps even out wear and tear on the wheels.
  • Eliminates need for brake test if locomotives uncoupled to carry out run around move.

Compared to stations with stub platforms, balloon loops allow:

  • Fewer tracks and platforms are required
  • Arrivals into some platforms do not block departures from other platforms
  • Time is not lost while drivers change ends and reset the train for the other direction
  • If the driver changed ends and discovers a hidden fault, then delays to trains are less likely

Disadvantages[edit]

The major disadvantage is that a balloon loop is very space consuming. Another disadvantage is that the sharp curves cause noise, as well as wear on wheels and rails. Also, if the platform is located on the curve, the gap between the platform and railcar door is a hazard. The former South Ferry station on the New York City Subway solved this problem by using gap fillers that extended out to the railcar door when the train triggered a switch on the tracks. The older station had been closed, but was reopened as a result of damage to the newer station caused by Hurricane Sandy.

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 reversing 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. This was the case on the Charing Cross, Euston and Hampstead Railway (now part of the Northern line of London Underground). 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 at Golders Green depot (near the other end of the line), for use when there was an imbalance of car directions.[14]

To avoid this problem, 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 the space inside the balloon loops is used for storing coal, so that is it not wasted.

At the Olympic Park station in Sydney, the loop is flattened where the platforms are located, so that the platform faces are straight.

References[edit]

  1. ^ MTA Capital Construction - Second Avenue Subway Planning Study
  2. ^ "Truckee Donner Railroad Society". Retrieved 2012-05-01. 
  3. ^ "Paulsboro - The New Omniport" (video). South Jersey Port Corporation. 
  4. ^ Trackmaps (November 2008). 5 Southern & TfL (Map). Railway Track Diagrams. Cartography by John Yonge (3rd ed.). p. 18 Romney, Hythe & Dymchurch Railway, E inset. ISBN 978-0-9549866-4-3.
  5. ^ gvb.nl
  6. ^ gvb.nl
  7. ^ Trackmaps (November 2008). 5 Southern & TfL (Map). Railway Track Diagrams. Cartography by John Yonge (3rd ed.). p. 43 Piccadilly line: South Harrow & Heathrow - Acton Town, D inset. ISBN 978-0-9549866-4-3.
  8. ^ Trackmaps (March 2005). 4 Midlands & North West (Map). Railway Track Diagrams. Cartography by John Yonge (2nd ed.). p. 40 Hunts Cross - Moorfields. ISBN 0-9549866-0-1.
  9. ^ Railway Digest February 2013, p54
  10. ^ Balloon loop
  11. ^ "Grain Loop". Rail Geelong. Retrieved 2013-12-28. 
  12. ^ http://www.street-directory.com.au/sd_new/mapsearch.cgi?star=5&heading=&x=120.27979366673421&y=-20.581211070081974&level=4&StateID=3
  13. ^ http://www.african-minerals.com/operations/maps
  14. ^ Bruce, J. Graeme (1988). "7. The First of the Standard Tube Stock 1923/25". The London Underground Tube Stock. Shepperton: Ian Allan. pp. 56–57. ISBN 0-7110-1707-7. 

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Balloon_loop — Please support Wikipedia.
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