Railway Track gauges – Further thoughts

Readers of this blog will have encountered my previous post in which I postulated that rail track gauges have clustered into various sets related by the mathematical constant known as the Golden Ratio. In this post I develop this idea further.

With this in mind I then tried to derive what might have been a more optimum set of railway gauges from the golden ratio. I was working on the basis that tramways with gauges in the region of two foot have proven a good solution for industrial use, so derived complimentary gauges bigger and smaller. See the table:

Based on 600 mm Based on 2 foot
mm feet / inch mm inches
Miniature (Leisure)




9 1/8

Minimum (Leisure / Horticulture)


14 5/8


14 7/8

Narrow (Industry / Farm / Intervillage)


23 5/8



Medium (Urban tramways / large island network)


38 2/8


38 7/8

Broad (Continental standard)


61 7/8


62 7/8

In doing so I made the presumption that the rail system would largely be structured like that which we have in the UK. The biggest gauge would be the “Standard gauge” and form the national network. Standalone rail systems such as light railways, industrial railways and various tourist lines could pick a smaller gauge reflecting the limited scope of the network.

In this post I look at the option of standardizing on a narrower gauge. The biggest gauge is only for the most intensively used routes, similar to the role played by standard gauge on the mostly narrow gauge Japanese railway network.

As before, I look at what nations have the highest railway usage. Here are the top ten countries for passenger modal ratios (market share in person kilometres) on Wikipedia.





















 United Kingdom















I’d qualify this by saying that it does not include China, India and Russia which would also be very high. Two of those are soviet countries where the society was planned around public transport to the extent that railway use has been “locked in” by the built environment. All three are very large in land area meaning  cars are not suitable for longer journeys within the territory.

Of those on the list, all have standard gauge railways. Top two Japan and Switzerland have extensive metre-ish gauge networks. India also has extensive metre and two foot gauge networks in rural areas although is busy eradicating these whilst building standard gauge metros in its biggest cities.

Most nations with alternative track gauges regard themselves as hamstrung by an unfortunate mistake and wish they could be “normal” standard gauge. Nonetheless Western nations with standard gauge networks, even those well invested with modern equipment seem to do very badly in terms of modal share. European countries seem to major on passenger transport with little share of freight, whereas “pioneer countries” like north America or Australia are all about bulk commodities and intermodal freight and carry virtually no passengers. Yet even European countries have modest rail modal share in spite of the quality of the railway and the apparent enlightenment of national government to the environmental impacts of road transport.

The poor modal share does not apply however to Japan. Rather Japan was occupied by the United States and certainly builds better cars than then the United States so why has the share of railway traffic remained so high?

I think part of the reason for the permeation of rail travel into Japanese life is the result of separation of the real people movers, the Shinkansen, from the everyday track gauge. The flexibility and lower start-up costs associated with a narrow gauge facilitate the proliferation of tracks and trains into the everyday travel patters on the society. As Japan realized, this in turn created a demand for a wider gauge railway network for express passenger service.

The narrow gauge railway network, in effect, performs the role of light rail and feeds traffic from the intermediate towns and cities into the high speed railway. We might call this the Shinkansen principle because the choice of gauge creates a strong distinction between the quotidian railway and the high capacity trunk route.

Choosing a track gauge for required performance

Narrow gauge seems quite adequate for almost all the everyday railway that serves town and country. Your ordinary seated carriage ought to seat four abreast in some degree of comfort, which requires a minimum width of about 2.75m and this coincidentally happens to be close to what the UK runs. British standard gauge train dimensions are exceeded on many 3’6″ gauge railways (1067mm, CAP gauge). Trams can be narrower due to the likelihood people will stand in peak periods.

Express speeds on CAP gauge of 160 kph has been achieved. This may be pushing the technology close to its limits, but shows that CAP gauge is more than sufficient for most rural or suburban railways that rarely need such speeds. With regard to freight, Queensland and South African railways run some of the heaviest iron ore trains on their CAP gauge. Of course the carriage of standard shipping containers would not present a problem – albeit not double stacked!

This leaves the option open to use a broader gauge for the small number of corridors with greater requirements for high speed or capacity (volume rather than mass). For example, double stack trains have a height of over 6m. The Channel Tunnel Shuttle (car carrier) has a width of 4.1m. The Dutch have recently built a freight railway (Betuweroute) that allows both these dimensions. These trains would of course be barred from the regular network. Given a broader gauge, double deck passenger stock would likely have been almost universal.

The engineering dictum “if it looks right it is right” can be applied here. A very large passenger train and tram are shown here, both on the same track gauge. Clearly these are built to different scale and demand the same of their track. Whilst the track gauge is the same in this case, in practice neither vehicle could run on the other’s right of way anyhow. A different track gauge for local and light railways than from long range heavy haul would be logical.

Running gear and track gauge

The choice of track gauge largely determines the appropriate design of running gear for a given application. Conventional railway coaches use twin axle bogies at each end with outside frames. Other options are simple two axle wagons, articulated stock which share bogies between two coaches, Talgo system which takes this concept further with only one pair of wheels and does away with the rigid axle. The inside frame bogie has recently become popular because it reduces weight and aerodynamic drag.

We might imagine a wider gauge would have encouraged a diversity of systems to compliment the outside frame bogie which dominates railway traffic. The Talgo system of articulation, a lightweight system which relies on independent wheels instead of solid axles, might have proved popular for single deck stock on routes where traffic was insufficient for double deck trains. Inside frame bogies, such as the Bombardier Flexx Eco which is now becoming popular on standard gauge, might also have arisen earlier were the space between wheels greater so as to reduce difficulties packaging the required systems between the wheels.

A likely system of gauges

Based on my previous post suggesting a relationship of track gauge defined by the golden ratio, I suggest that the “standard gauge” would be CAP gauge or thereabouts. Using cunning numerology I found that a slightly broader metric equivalent of 1100 mm for the standard gives a round number of centimetres for all gauges down to 260mm (this is also, bizarrely, the popular 10 1/4 gauge used for miniature railways). 1100mm is actually used for some light railways today. The 68cm gauge is almost 2’3″ which is the gauge used by the Tallyllyn and Corris railway in Wales, these fulfilling the same role as the 2′ gauge used in the other Welsh quarry railways.

So our big, fat, trans-continental gauge is about one foot wider than Stephenson gauge (exactly one foot wider under “something between” in the table below). Also interesting is that the Stephenson gauge falls almost exactly halfway between our broad and our narrow gauges. Since our  CAP-like gauge which forms the bulk of the railway network will allow most trains to be lighter than standard gauge ones, this means that despite the bigger, heavier trains on broad gauge, the average train of this counterfactual would be lighter than the average train in real life.

Iterate from CAP (3’6”) …Somewhere between From 1100 mm
mm inches mm inches mm inches
Miniature (Leisure)


9 15/16




10 4/16

Minimum (Leisure / Horticulture)


16 1/16


16 3/16


16 9/16

Narrow (Industry / Farm)




26 3/16


26 12/16

Standard Gauge




42 5/16


43 5/16

Broad (Intercity)




68 8/16


70 1/16

Separation between local and national

The great thing about different track gauge for local and long distance movement is that it will enforce two tiers of management of the network. The management of the highways might be illustrative. The narrow gauge would represent the ordinary roads managed by the local highways body, whereas the broad gauge represents the motorways and trunk roads and be run by a national or trans national body. Local administration narrow standard gauge becomes more responsive to local needs. The broad gauge system might be expected to run at a profit.

A disadvantage might come with freight transport as it would imply two breaks of gauge over long trips narrow gauge for the feeder and distributor trips, broad for the trunk haul). In practice the freight traffic might have been expected to work its way across the narrow gauge networks.

An application where such a scheme could have potentially worked very well is on continental Europe. Today the problem is with national integration: unlike the alternative of road transport each national system remains stubbornly self contained. Under the Shinkansen scheme each country could have been responsible for its own CAP gauge network. The long distance railways (those represented by TEN routes or high speed lines) would then be to the broader gauge. The advantage would be to allow each nation its sovereignty but also reserve a more strategic function for the broader routes.


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