Why dreams of speed are slowed by technological and economic challenges

At the start of his first term in 2009, United States President Barack Obama backed plans for a high-speed rail line between Los Angeles and San Francisco. Faced with production costs deemed exorbitant (estimated at around 50 to 60 billion dollars at the time), the famous businessman Elon Musk is skeptical. In 2013, he suggested replacing the project with a new system he called “Hyperloop alpha”. Small capsules 2.20 meters in diameter which would circulate on air cushion in two aerial tubes, under vacuum, at more than 1200 km/h for an initial investment estimated at 10 billion dollars.

Seduced by this futuristic scenario, many start-ups have tried to materialize the idea. Nearly a decade later, however, progress remains limited. Virgin Hyperloop, powered by British entrepreneur Richard Branson’s money, has certainly been tested in the Nevada desert, reaching 387 km / h. In November 2020, she even transported passengers for the first time, at 172 km / h, but that was before announcing her conversion to freight. The section that was to see the light of day in 2020 for the Universal Exhibition in Dubai has still not come out of the ground.

The contracts, however, are multiplying. Hyperloop Transportation Technologies (HyperloopTT) signed an agreement on March 21, 2022 to open a line between Venice and Padua, Italy for the 2026 Winter Olympics. In Canada, TransPod most recently succeeded in raising 550 million dollars to try to connect Calgary to Edmonton. In France, the HyperloopTT test track project in Toulouse remains at a standstill but that of TransPod in Haute-Vienne is in progress.

Concept of the Hyperloop Cheetah, which is a variant of Elon Musk’s Hyperloop project. It is equipped with wheels, rows of 3 seats and airlocks at the ends – RichMacf / Wikimedia CC BY-SA 4.0

We are therefore still very far from the goal, as we explained with Hervé de Trègulode in a recent research article. The announcement effects outweigh the concrete results because the technical challenges remain numerous: that of the rigidity of the tubes installed between pylons in the open air; ensure that the air in the tubes never crosses the sound barrier; compress and cool the air sucked in… To the point that François Lacôte, former technical director of Alstom does not hesitate to speak of Hyperloop as a “tremendous technical-industrial swindle”.

To the engineer’s critical eye, we can add some economic considerations by questioning the relevance of these “pods” which are sometimes presented as a “fifth means of transport”. Considering physical speed is not enough: it is also necessary to consider economic speed.

Money is time

Economists have long shown the benefits of speed gains. Indeed, time is money. TGV users are ready to pay more to go faster. But to what extent is the additional cost acceptable? Because money is also time. How much work time will it take to buy speed?

It is in fact a question of dividing a journey into two stages. There is the time actually spent moving around, and, before that, the time spent working in order to be able to afford the price of the train or plane ticket. In this first period, it is as if the user were moving at an economical speed.

A pod, scale model, on a test track in the Netherlands
A scale model pod on a test track in the Netherlands – Jeroen Juumelet / ANP / AFP (via The Conversation)

Let’s take an example. For a Concorde trip twenty years ago (the last flight took place in 2003), the cost was close to one euro per kilometer. The net minimum wage at the time was 6 euros per hour, which therefore gives an economic speed of 6 km per hour of work and nearly 2000 hours of work for the Paris-New York round trip. In short, nothing “supersonic”.

The observation was also valid for a high salary, for example 10 times the minimum wage. The economic speed of the Concorde was then only 60 km/h whereas a subsonic flight costing 10 times less (10 centimes per kilometer) corresponded to an economic speed of 600 km/h (and 60 km/h for the smicard).

The commercial failure of supersonic flights finds its origin there: the Concorde did not pass the barrier of economic speed. Symmetrically, the successes of traditional air transport and even more so of low-cost airlines, whose tickets cost an average of 5 cents per kilometer, are based on the trend increase in their economic speed.

Last flight for the Concorde between New York and London on October 24, 2003: according to the economist, there was nothing supersonic about it
Last flight for the Concorde between New York and London on October 24, 2003: in the eyes of the economist, it was nothing supersonic – Nicolas Asfouri / AFP (via The Conversation)

High physical speed is, in fact, irrelevant when economic speed is low. Because, when two speeds are combined (to calculate here a “generalized speed”), it is always the slowest which weighs the heaviest in the calculation.

Take the example of a cyclist who climbs a pass in the Alps at 10 km/h and descends at 60 km/h to reach his starting point. Its average speed is not 35 km/h (the sum of the two speeds divided by two) but 17.1 km/h. For most mathematicians, it is a harmonic mean and not an arithmetic mean. The curious reader will be able to calculate that even when descending the pass at the speed of light, the cyclist barely reaches 20 km/h.

It’s a bit the same when you combine economic speed and physical speed. The first corresponds to the ascent, the second to the descent.

What time savings and for whom?

By projecting ourselves into the imagination of Jules Verne, the search for speed makes us dream. It is implicitly considered as a sign of progress, but sometimes at the risk of going against common sense if the economic speed remains low for the majority.

The wide spread of rail, then road and air transport was possible because they made it possible to increase the speed of travel. But the greatest success of these modes of transport is their democratization, which has only been possible through a general increase in economic speed.

Even with a liter of petrol at 2 euros, an hour’s minimum wage today allows you to travel around 100 km with a small car compared to barely 30 km at the beginning of the 1970s. In 1980, a one-way plane ticket return to Tunis required 123 hours of work at minimum wage compared to 15 in 2020.

Gains in physical speed are of no interest if they cannot be democratized. However, Hyperloop-type projects will have great difficulty in offering travel costs that are accessible to as many people as possible due to their low potential throughput.

By flow, we mean the quantity of passengers that can be transported on an axis in one hour. Today, in a TGV train with two elements and two floors, we can put 1000 to 1200 passengers. With modern signaling systems, it is possible to pass 15 trains per hour and therefore 15,000 to 18,000 passengers per hour.

TGV trains can carry up to 18,000 people per hour on one axis: it seems very difficult for 20-seat pods to match this performance
TGV trains can carry up to 18,000 people per hour on one axis: it seems very difficult for 20-seat pods to match this performance – Philippe Lopez / AFP (via The Conversation)

In Hyperloop type capsules, carrying 20 people, it would take, to achieve the same result, a departure every four seconds. The problem seems insoluble technically but especially in terms of security. In case of problem for a capsule, how to prevent that a certain number of the following ones do not come to be embedded in this one?

Focusing on physical speed is useless if the throughput is low, even though the necessary investments are gigantic. How can infrastructures costing tens of billions of euros be justified if they only benefit a privileged minority?

It could be objected that the construction of the rail network also required very large investments. In the 19th century, one km of railway cost fifteen times more than one km of road. But the railroad has made it possible to increase traffic in such a way that we have been able to amortize the costs of building the infrastructures. In the 1970s, engineer Michel Walrave demonstrated that the same was true for the first high-speed line projects.

The question of throughput is therefore crucial because it determines the private and public costs. We then touch upon questions of a profoundly democratic nature. If the State finances the construction of infrastructures, how can we justify the mobilization of taxes from all to serve a privileged minority? It’s a bit like deciding to subsidize space travel for billionaires (for whom the economic speed is, by the way, 100 meters per hour for a minimum wage).

For Hyperloop, even if a democratization would be possible one day, let’s not forget that the search for speed is structurally confronted with diminishing returns. By doubling the speed of the trains between Paris and Lyon, the journey time has been halved, from 4 to 2 hours. But by doubling the speed again (from 250 to 500 km/h), we would gain only one hour and only half an hour by multiplying it again by two (1000 km/h). The gain in time would be increasingly minimal to the point that the question would arise: is the game worth the candle? This is also the question faced by Hyperloop-type projects.

This analysis was written by Yves Crozet, professor emeritus at Sciences Po Lyon and transport economist at the University Lumière Lyon 2.
The original article was published on the site of The Conversation.

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