The rail gauges selected to build a railroad is chosen for a variety of reasons. These may include a need to connect to other railroads, the type of terrain to be crossed and the costs of construction and maintenance.A railroad may start as a single isolated line, for example from a mine or quarry to a port, and be built using a gauge that is ideal for the purpose of the line and the conditions along its route. Later a mainline railroad, built using a different gauge chosen for equally valid reasons, connects the port to other cities and industrial centres. Where the two railroads with their different gauges meet is a “break of gauge” location.
Break of gauge locations are a source of complaints from passengers and an added expense to industries. While passengers can be easily moved, often with complaints, from their seats on one train to seats on another train, this is not always easily done for freight, particularly bulk freight. Losses and damage are common problems. On some journeys passengers and freight would change gauges several times. Schemes devised to overcome this problem have led to some very innovative, and sometimes strange, solutions.
Separation of Gauges
The simplest method of dealing with break of gauge problems, and the method most commonly used in the early days of railroading, was to keep the two gauges completely separate. So each gauge would have its own platforms, loading docks, servicing facilities, etc. It was not uncommon for passengers to have to use a taxi to get from a station on one gauge to the station on another gauge to continue their journey. Likewise, freight would have to be transported between the different loading facilities by road wagons.
The image above shows the situation at Albury on the border between the states of New South Wales and Victoria in Australia. Railroads in Victoria (on the left) were built using the Irish Broad Gauge (5 ft 3 in, 1600mm) while those in New South Wales (on the right) were built using the Stephenson or Standard Gauge (4 ft 8 ½ in, 1435mm). Passengers moving from one system to the other simply crossed the platform to the train waiting on the other side to continue their journey. A similar but very labour intensive arrangement existed for transferring freight between the two systems.
Multi Gauge Track
More commonly tracks of a different gauge or gauges would be laid within track of another gauge. This allowed trains of different gauges to share the same platforms, loading docks and servicing facilities but obviously made track switching and signalling more complicated and expensive.
The image above shows dual gauge track (in the foreground and extending into the distance) merging with triple gauge track coming from the right.The dual gauges in the foreground are Irish Broad Gauge and Cape Narrow Gauge (3 ft 6 in, 1067mm) which both share a common right hand rail.The triple gauge tracks merging from the right are Irish Broad Gauge (the first and third rails from the left), Cape Narrow Gauge (the second rail and the shared third rail from the left) and Standard Gauge (the second rail, which is shared with the narrow gauge, and the fourth rail).
Using shared rails reduces the construction costs but is not always possible. If the difference between the gauges is small then there will not be enough room between the two outer (unshared) rails for the switches, rail plates and spikes. In the image of the turntable above the rails had to be custom made to fit the three gauges together without a common rail. Note the very small gap between the Irish Broad gauge (the outer rails) and the Standard gauge tracks.
One solution to the break of gauge problem is to replace a single gauge line, in its entire length, with dual gauge track. The image above shows one example where the gauges are too close to use a common rail. This allows passengers and freight to make the entire journey without having to change trains.
Break of gauge locations with four or more gauges are rare due to their costs and engineering difficulties. However, examples can be found in industrial systems, such as locomotive or rolling stock manufacturing plants and in railroad museums.
In a bogie exchange, the wagons are lifted off their current gauge bogies which are rolled away. The new gauge bogies are then rolled into place and the wagons lowered onto them. Most rolling stock (wagons and carriages) are designed to have their bogies replaced anyway so this system was not specifically designed for the gauge conversion of trains but it is ideal for the task. While the process can be time consuming the freight carried in the wagons does not have to be moved between wagons and this reduces losses and damage.
Diesel locomotives can also be gauge converted by this method but their more complicated bogie connections makes the process more difficult and time consuming. Some steam locomotives built after 1930 were designed to have their bogies and driving wheels gauge converted but there are records of only one such conversion ever taking place – a Pacific class steam locomotive R766 in Victoria Australia, which was converted from Irish Broad gauge to Standard gauge in 2014.
“Piggyback” or “Train on Train”
Rail wagons are commonly used to transport cars, trucks and other road vehicles between destinations. In the Channel Tunnel, for example, road vehicles are driven onto specially designed wagons at one end of the tunnel, the train takes the vehicles through the tunnel and they are driven off the wagons onto roads at the other end. Exactly the same principle, with variations, has been used to move rail wagons and even entire trains of one gauge over territory where a different rail gauge is in use.
The image above shows an example of a single wagon transport system designed to transport a wagon of one rail gauge over tracks of a different rail gauge. These systems are typically used in wagon repair facilities. In this case the upper wagons wheels are locked in position on rails that form part of the lower wagon.
The “piggy back” method has, on rare occasions, been used to carry entire trains across a different gauge. In the late 1950s when the narrow gauge Maree line in South Australia was being gauge converted, a set of standard gauge flat wagons were fitted with narrow gauge tracks on their tops. Narrow gauge wagons loaded with coal were pushed up a ramp at the end of the standard gauge train and along the “piggy back” track on the flat wagons. The coal wagons were then transported to the other end of the gauge converted section where the process was reversed. This continued for the year it took to complete the conversion of the entire line to standard gauge and ensured that a major power station continued to receive its coal supply.
There are a variety of systems in use that allow the wheels of a train to be changed from one rail gauge to another without using bogie exchange. The idea goes back to the 1800s when railroads in Great Britain were plagued with change of gauge problems. In the most advanced of these systems the entire train, usually without the locomotive unless it also has variable gauge wheels, rolls slowly through a gauge changing mechanism which unlocks the wheels, moves them closer (or further apart) on their axles and then locks them again in their new position.
In the image above, the train enters the shed at the far end on the Spanish side as an Iberian Gauge train (5 ft 5 21/32 in, 1668mm) and emerges at this end on the French side as a standard gauge train. Spain is the largest user of variable gauge systems.
Contributed by pware