Published by Australian Academy of Science
KEY TEXT Looking down the track at very fast trains This topic is sponsored by the Australian Government's National Innovation Awareness Strategy.

Australian trains are plodders. It takes the Indian-Pacific 18½ hours to travel between Sydney and Broken Hill, a distance of 1100 kilometres (at an average speed – including stops – of 60 kilometres per hour). Even the country's fastest train, the XPT, takes just over 4 hours to travel from Sydney to Canberra (310 kilometres).

Some people say we should use 'tilt' trains, which are faster than current Australian trains (but still slow by world standards) and can use existing tracks (Box 1). But most train enthusiasts know that when it comes to real speed, there are only two contenders: the current crop of 'very fast trains' that have wheels and run on steel tracks; and the more imaginative magnetically levitated trains, which excite the mind but are yet to be tested commercially.

How fast is very fast?

The fastest trains in commercial operation today are the French train à grande vitesse (TGV), the Japanese shinkansen  (or bullet train) and the German InterCity Express  (ICE). The TGV routinely travels at 300 kilometres per hour through the French countryside and has been clocked at 515 kilometres per hour in test runs. The bullet train averages 262 kilometres per hour between stations and has recorded 443 kilometres per hour in test runs, while the ICE has a top operational speed of 280 kilometres per hour and has recorded 408 kilometres per hour in trials.

These trains have several things in common:

• They all use electric motors (some very fast trains still run on diesel, but these are slower than their electric counterparts).

• They all have steel wheels that run on steel tracks.

• They have aerodynamic designs to decrease wind resistance - in some ways they look like long, thin aeroplanes without wings.

• They all require special lines to achieve their maximum operating speeds – in particular, these need to be as straight as possible, because very fast trains and tight bends don't mix well (Box 1: The centrifugal effect and tilt trains). Nevertheless, these trains can also run on conventional lines at reduced speeds, a great advantage when approaching major urban centres.

Let's look at one of the most successful of these trains, the TGV, in slightly more detail.

Innovations in the TGV

Many of the innovative aspects of the TGV are in the design and placement of bogies. Bogies consist of two or more pairs of wheels, their axles and a connecting frame that supports the carriages (usually called cars) above. At high speeds, the vibrations produced by contact between the wheels and the rails increase dramatically. This can cause the bogies to sway from side to side, which in turn can damage the track and, in severe cases, derail the train.

While developing the TGV, engineers found that increasing the distance between axles in the bogies could reduce this instability. In addition, since instability increased with increasing bogie weight, they moved the electric motors, usually mounted on the bogies, and suspended them from the bottom of the cars.

Bogie placement was also changed. Conventional train carriages have two bogies each, one towards each end. In the TGV, cars are attached to each other semi-permanently, with the front end of one car and the back end of the next car resting on a common bogie. In this way, each car effectively uses only one bogie (two halves).

Efforts are continually being made to reduce the overall weight of the train, largely because the lighter the train, the less stress there is on the track (therefore lowering maintenance costs). Reducing the number of bogies saves weight. In addition, new, lighter materials are used in the construction of the trains. Even the seats are now made of lightweight carbon fibres, magnesium and composite materials.

Wheels on tracks or levitated

While the TGV, the bullet train and the ICE all use established technology – electric motors and steel wheels – revolutionary technology has produced a high speed train which floats on a magnetic cushion of air above a special track.

Maglev

The maglev differs radically from its more conventional high-speed cousins. It doesn't have wheels and it doesn't run on a steel track. It doesn't even have an on-board motor. The motor that propels the maglev is in the special track, and the propulsion comes from magnets.

In maglev technology, electromagnets (devices that become magnetic when fed an electric current) are mounted on the train and in the track (usually called a guideway). The electromagnets levitate, guide and propel the train along the guideway (Box 2: How the maglev works).

Maglev vs conventional high speed trains

Maglev technology has several theoretical advantages over conventional high-speed trains. Since there is no wheel-to-track contact, less energy is lost due to friction and the trains create less noise. Maglevs also use less energy to achieve the same speed as conventional very fast trains.

In addition, since the motor is in the guideway rather than on the train, it is possible to increase its power on steep sections. This means that maglevs can climb steeper grades than conventional high-speed trains, reducing the need for tunnels.

Despite such advantages, maglevs remain commercially unproven. In comparison, trains like the TGV, the bullet train and the ICE have been formidably successful. Millions of people have travelled on them; hundreds of thousands use them each day. Each new generation of train gets faster, and they boast an impressive safety record.

One of the biggest barriers to maglevs is the need for a whole new infrastructure. Their guideways need to be constructed from scratch, a costly and financially risky venture, at least in the early stages. In contrast, conventional high-speed trains can run on existing tracks through urban areas, and the high-speed portions can be constructed in stages.

Safety of very fast trains

Very fast trains are safe compared to most other forms of motorised transport. For example, the TGV, which commenced operation in 1981, travels about 10 million passenger kilometres each year. It is yet to have an on-board fatality, although a number of people have died in collisions at road crossings.

But this is not to say that major disasters are impossible. In June 1998, an InterCity Express, travelling at about 200 kilometres per hour, derailed near Eschede in Germany, killing 102 people and injuring hundreds more. The cause of the accident is still under investigation.

The future of high speed trains

Commentators seem to agree that very fast trains – the conventional ones, at least – will form a significant part of the international transportation scene in coming decades.

But Australia is something of a special case. With our small population dispersed in relatively small towns and middle-sized cities across vast distances, the commercial viability of very fast trains remains in doubt. There is no shortage of ideas: some people talk of a high-speed train network linking Melbourne to Brisbane (via Canberra), and another, linking Melbourne and Darwin, has also been proposed.

Are we on the cusp of a transport revolution in Australia, or are our trains destined to remain plodders? Should we launch straight into technology, or should we consider the tried-and-true alternatives? Expect the debate to continue, full steam ahead.

Boxes

1. The centrifugal effect and tilt trains

2. How the maglev works

CREDITS

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