There’s no shortage of articles proclaiming the benefits of Hyperloop and Maglev transportation. Yet such features rarely have any serious engineering analysis. In 2012, Elon Musk published a technical paper proposing his Hyperloop concept of pods in vacuum tubes. In this, he recorded his disappointment that the home of Silicon Valley is building a high-speed railway which he, and others, saw as an outdated technology.
But are they? As shown below, the permanent way has evolved into a modern well-engineered system for guided transport that is hard to beat.
The railway’s long history is certainly no bad thing. Like all modes of transport, railways have been developed from crude beginnings and now benefit from many years of worldwide experience, research and development, which include painful lessons learnt.
Wagonways to steel rails
From medieval times, wagons in mines have been moved on wooden tracks in mines. In the 17th and 18th centuries, Britain’s various timber wagonways (or waggonways) were built to carry coal. Possibly the world’s first overground wagonway was the Wollaton Waggonway which opened in 1604 near Nottingham. This was used to haul coal for two miles from Strelley to Wollaton.
Another early wagonway was that between Tranent and Cockenzie in East Lothian, Scotland, which opened in 1722. This supplied coal from the mine at Tranent to the salt pans at Cockenzie, three miles away down an average 1 in 50 gradient which required a substantial embankment to maintain an even grade. The coal was carried on wagons that had a brakeman to control their descent and the empties were returned by horse. The line cost £3,500 – the equivalent to £400,000 today.
With the development of the iron industry in the late 18th century, iron plates with inside flanges replaced the wooden timbers that had to be frequently replaced. However, the accumulation of dirt on the plate rail reduced the load that could be hauled.
William Jessop realised that the solution to this problem was raising the rails. To do so he developed three-foot long fish belly I-section rails which were laid on stone pads to give horses a smooth path between the rails. Their first use was for a three-mile long railway in Loughborough in 1789. This seems to have been the first use of flanged wheels on rails and, if so, was the world’s first railway.
When steam locomotives were first introduced, there were concerns that their wheels would not grip the rails, so some early locomotives had rack and pinion propulsion. However, it was found that the friction between wheel and rail was generally sufficient to haul trains.
What was a problem was the weight of the locomotives, which broke the cast iron rails of the time. It was the introduction of wrought iron rails that enabled steam locomotives to be used on early railways. Originally, these rails were laid on stone pads. However, where the ground was particularly soft, it was found that wooden sleepers were required to spread the load, which became the accepted practice.
To prevent track movement, early engineers considered anchoring it in place. However, as speeds and weight increased, it soon became apparent that the best way to carry the railway’s load without damaging the track was to secure it in a layer of stones, to provide the right balance of rigidity and elasticity. It also enabled track geometry to be relatively easily maintained by packing stones under the sleepers.
Switches were also developed from the early days – initially stub switches which had moveable rails cut off squarely at the end to line up with the fixed rails. These were susceptible to impact loads and were progressively replaced by those with switch and stock rails which were developed to carry heavy loads safely at high speeds.
The first steel rails were laid in Derby station in 1857. The transition to steel rails was hastened by later developments in steel making. By the late 19th century, the basic configuration of the permanent way had been established and it was carrying heavy loads and passenger trains travelling at speeds approaching 100mph.
Since then, there have been many developments in track manufacture, construction and maintenance, including the introduction of continuously welded rail to eliminate track joints. As a result, tight geometrical tolerances can be sustained to safely carry frequent 200km/h passenger trains and heavy freight trains.
However, ballasted track is at its technical and economic limit for trains operating at 300km/h, which has high dynamic forces and requires more demanding tolerances. This drove the development of slab track, which was used for 19,000 kilometres of China’s 29,000km high-speed rail network and will be used for HS2.
Efficient surface transport
In parallel with the development of modern track, rolling stock suspensions and wheelsets have been the subject of a huge worldwide research and development effort to ensure that trains can reliably run smoothly and safely at speeds of up to 225mph or carry freight trains weighing thousands of tonnes.
After these various developments, a railway now offers the most efficient system of surface transport that carries heavy loads and operates at high speeds because:
Loads are efficiently distributed – the maximum dynamic wheel force of 350kN results in a pressure on the rail head of 2.8kN/mm which is progressively reduced through the rails, sleepers and ballast to 0.5N/mm. Hence, high dynamic loads from high-speed trains and the large axle weights of heavy freight trains can be carried on a relatively narrow formation.
Low resistance to motion – the rolling resistance of steel wheels on steel rails is about 0.1% of the weight of the train, compared with about 1% for car tyres on a road. At speed, aerodynamic resistance becomes the dominant factor. In this respect, close-coupled railway vehicles have lower resistance to motion than the same number of individual vehicles.
High passenger and freight capacity – the ability to couple many vehicles together offers high freight and passenger capacity, despite the need to distance trains for safe separation. A Eurostar train can carry 900 passengers. When completed, HS2 will have capacity for 18 such trains an hour out of London, about 16,000 passengers per hour. A two-lane motorway carries around 4,000 people per hour.
Collecting electricity on the move – as trains are part of a guided system, they receive megawatts of power as it is generated. Electric trains are thus highly efficient and take advantage of the greening of the grid to reduce carbon emissions.
Connectivity – new railways connect into the existing railway network to offer far more journey opportunities than those on the new line.
However, permanent way is expensive, so these benefits can only be realised if there is sufficient traffic.
Hype and reality
So, what of Hyperloop? Most of the literature promoting it concerns only the pod and its tube. Yet a transport system has to be much more than this. For example, claims have been made that the tube/pod system is now proven, without any mention of switches. Any serious engineering analysis of all aspects of the Hyperloop system shows that many significant problems have yet to be addressed before it can operate safely. These include switching very high-speed pods between tubes, hyperloop tube expansion, emergency evacuation from inside the vacuum tube and signalling systems.
Readers familiar with the Railways and Other Guided Transport Systems (Safety) Regulations may imagine the task faced by those who wish to obtain authorisation to operate a system that carries people in vacuum tubes for hundreds of miles at speeds of around 750mph.
Even if it were possible to prove the safety integrity of all these aspects, the cost of constructing vacuum tube infrastructure over long distances must be justified. Yet, with its small pods, Hyperloop has a poor passenger capacity, as shown in Elon Musk’s paper which states that it would carry 840 passengers an hour. This is just 5% of HS2 which will have the capacity to carry 16,000 passengers out of London.
Unlike Hyperloop, Maglev has demonstrated its technical feasibility. Although its electromagnetic levitation eliminates a train’s rolling resistance, this offers no real advantage. At high speeds, rolling resistance is a tiny fraction of the aerodynamic drag and comparable with the energy Maglev needs for its levitation. What Maglev does offer is maximum speeds of around 300mph, compared with 225mph for high-speed rail.
Yet, as with Hyperloop, it has no economic justification. Between London and Manchester, a Maglev offers a time saving of around 15 minutes over HS2 and could never justify the huge infrastructure cost over this distance, especially as it cannot be plugged into the rail network to offer more journey opportunities.
Both these technologies, but particularly Hyperloop, have attracted a large amount of investment, been promoted in reports by reputable consultancies and received uncritical press coverage. The money this attracts then further adds to their false credibility. Furthermore, various countries have backed proposals to build a hyperloop. It seems that the hype and attraction of these futuristic proposals transcends engineering realities. The danger is that decision-makers might consider Hyperloop and Maglev to be realistic proposals, to the detriment of proven transport technologies.
The reality is that, over the years since they were first proposed, those promoting Hyperloop and Maglev have yet to demonstrate that they have analysed and satisfactorily addressed all safety, engineering, operational and economic aspects of their systems. It is difficult to see how they ever can.
Hence, a well-engineered modern railway will continue to provide the most efficient way of transporting freight and passengers where the cost of its infrastructure can be justified. Its permanent way will continue to be just that.