Railroad Tracks With Different Widths, Why?

Railroad tracks are various, created with different widths. It is called “gauge” in railway engineering. The different gauges exist as different standards. The rule of thumb is that the broader the gauge, the heavier loads the track can carry and the faster speeds can be attained.

Railroad Tracks With Different Widths
Map of different main line railway tracks in the world.

Most main line railway gauges are matters of agreement. The most common gauges are the standard gauge (1435 mm), the Eastern European gauge (1524 mm) and Iberian gauge (1668 mm)

The rule of thumb is that one freight train can carry as much cargo on tracks as lorries on a four-lane motorway in an hour.

But there are many local, makeshift and light railways where the main line gauge is not needed, and they employ narrower gauges.

For example the Finnish main lines use the Eastern European 1524 mm gauge, but the Helsinki and Tampere trams use the 1000 mm narrow gauge.

Is there a technical advantage for railroad tracks one over another?

Railway tracks (gauges) are broadly classified into three groups: narrow, standard, and broad. Each of these three has its own advantages and disadvantages. However, within these three groups, there are a plethora of various gauges that differ by only a few millimetres or inches, and which have no significant advantages over each other but exist for a multitude of reasons.

railroad tracks

Dealing with the three broad groupings first.

Narrow gauge is defined as anything narrower than standard gauge (1,435 mm or 4 ft 8 1⁄2 in). It is cheaper to lay/construct since it requires less width of land and materials. It also allows tighter turns and smaller train sets (which in themselves allow tighter turns). This ease of turning also means you can squeeze narrow gauge tracks into places that couldn’t accommodate wider gauges, such as industrial sites, mine-workings and modern urban light railways.

The disadvantage of a narrow gauge is stability. Particularly, heavy loads at high speeds will be more susceptible to derail. There may be an issue of comfort for passengers. Also, with longer train sets, the wheels may bind on the track when cornering.

Broad gauge is anything wider than standard gauge (1,435 mm or 4 ft 8 1⁄2 in). Broad gauge is more expensive to construct, requires a wider turning radius and larger train sets, however, this is offset by increased stability — especially for large heavy loads at speed — and increased space for larger engines to be mounted.

Standard gauge (1,435 mm or 4 ft 8 1⁄2 in), is somewhat of a compromise between narrow and broad.

Why do we have a standard gauge and why is it such an odd number?

Well, rail predates steam trains. During the industrial revolution, it was common to have factories and mines with small horse drawn or cable drawn railways. Each site would have its own gauge of track, which wouldn’t matter much since bogies didn’t transfer from one site to another.

Then comes George Stephenson and his Rocket — the first practical steam engine — and railroads start to expand across the country. Various operators constructed lines with various gauges.

Brunel’s Great Western Railway from London to Bristol used a broad gauge of 7 ft (2,134 mm). This was a reasonably sensible unit, being a whole number of feet, but was very broad, even by broad gauge standards. Also, his system of construction, with sleepers parallel to the track and occasional cross braces, made the ride less comfortable than it should have been.

Railroad Tracks With Different Widths, Why?
Railroad Tracks

Above: a replica of Stephenson’s Rocket in York Railway Museum, England.

Most of the track in England copied the precedent set by Stephenson. He didn’t choose the number 4 ft 8 1⁄2 in for any special reason. The work sites where he first built lines used a gauge of 4 ft 8 in. This was slightly increased to today’s 4 ft 8 1/2 in, to allow better cornering, when Stephenson build his first major railway, the Liverpool and Manchester Railway, between 1826 and 1830.

For a time, there was no standardisation. Even George Stephenson, and his son Robert, used a variety of gauges on their projects. However, as networks expanded and began to join together, the incompatibility of the gauges became an issue.

In 1845, a Royal Commission on Railway Gauges reported in favour of a standard gauge of 4 ft 8 1⁄2 in. This choice was largely made due to this gauge being the most prevalent in use in Great Britain at that time. The Regulating the Gauge of Railways Act 1846 set this standard gauge for all new lines in Great Britain (Ireland was different) and after a period of mixed operations, all major railways in the Great Britain switch gauges.

Due to British industrial dominance and the British Empire, this standard gauge was spread to a great many other counties. However, a few countries didn’t follow the British lead for a variety of reasons. Russia and then the Soviet Union adopted a 5 ft gauge (actually 1520 mm or 4 ft 11 27⁄32 in) that had been used in the UK and USA before standardisation.

They continued to use that gauge building to the modern days with 84 446 km of Russia’s 85 281 km of railway lines using this 5 ft gauge, making it the second most used gauge in the world. Soviet influence in the second half of the 20th century saw this 5 ft gauge adopted throughout Eastern Europe and Central Asia. The geographical political isolation of the Soviet rail system meant that the difference in gauge between the Soviets and other countries wasn’t a significant issue.

In France, an extensive rail network was constructed during the industrial revolution. This was further intensified during the Great War. However, there wasn’t the same standardisation of gauges in France as there was in the UK. While most tracks were laid in standard gauge, about 1/3rd of the lines were narrow gauge.

With the advent of road transport, rail transport in France reduced and was rationalised. Many of the narrow gauge lines were closed as they faced road based competition. Today some narrow gauge lines still exist, such as St Gervais-Vallorcine line in the Alps, however, most lines, including all the high-speed lines, are in the standard gauge of 1435 mm

Spain’s gauge is odd. Spain didn’t use imperial feet (like the UK and USA) or metres (like France) they had the Castilian foot. Their first rail line used a gauge with a nice round number of 6 Castilian feet (1,672 mm or 5 ft 5 13⁄16 in) this was later adjusted and standardised across the Iberian Peninsula to become 1,668 mm (5 ft 5 21⁄32 in). However, many small narrow gauge railways were also constructed with about 1,250 km of metre gauge railways still existing.

The situation in Spain is becoming more complex as new high-speed rail lines are being constructed using standard gauge (1435 mm) so as to allow cross Europe network connections.

I could keep going on talking about various nations and their choice of gauge but in fact, the gauge is only a part of the story. Look at this:

Railroad Tracks With Different Widths, Why?

Above map shows the variation in rail electrification standards throughout Europe.

  • Orange — 750 V DC
  • Pink — 1.5 kV DC
  • Cream — 3 kV DC
  • Blue — 15 kV, 16.7 Hz AC
  • Green — 25 kV, 50 Hz AC
  • Grey — Non-electrified

Yes, that is a mess. It doesn’t matter so much for diesel-electric units, but for electric train sets such there is no pan-European standard for the electricity supply for the railways. Even within countries like France and the UK, there are two different standards of voltage in use.

Then there is the issue of load gauge — that is the width and height that train sets can be in order to fit under bridges, through tunnels and into train platforms. There is little or no standardisation of load gauge and many networks, such as that in the UK, are stuck with ancient rail networks with small load gauges that would cost a fortune to increase.

For gaining further knowledge, please check here, Why are there different widths for railroad tracks?

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