Note: this post is secretly about Hyperloop and Elon Musk’s most likely fraudulent claim about the Northeast Corridor. But it’s an interesting discussion more in general. Not all such technology is vaporware the way Musk’s efforts are. See more on The Boring Company’s false claims in a piece I published at Urbanize.LA a few days ago.
The upper limit of conventional high-speed rail seems to be 360 km/h. In Japan, experiments at that speed have succeeded, but there already are problems with noise, stopping distance, and catenary wear, and currently trains top at 320; plans to go at 360 depend on a future Shinkansen extension to Sapporo. In China, the maximum speed is 350, with trains capable of reaching 380 but not doing so in practice. In Continental Europe the maximum speed for new lines is 320-330 km/h, whereas in Britain HS2 is designed for about 350 km/h (220 mph).
Faster technologies exist, in service, today. Shanghai’s Transrapid tops at 431 km/h in service, and JR Central’s under-construction maglev line is targeted at 500 km/h, with tests at 600. Vactrains can go even faster, but are still untested technology (and this includes Hyperloop variants). The question is, where is there room for such technology? So far, Siemens’ attempts to sell Transrapid failed beyond the Shanghai airport connector, an orphan 30 km line going from the airport to the edge of the built-up area of the city. JR Central is building the Chuo Shinkansen maglev between Tokyo and Osaka, but so far there are no plans to extend this technology elsewhere – even within Japan, the state is continuing with building Tokyo-Sapporo as conventional Shinkansen rather than maglev.
The Tokyo-Osaka line is somewhat sui generis. JR Central is currently running about 14 trains per hour at the peak on the Tokaido Shinkansen between Tokyo and Shin-Osaka, each with 1,323 seats, and they’re generally full. It is also old – as the first HSR line in the world, it has a curve radius of 2.5 km (newer lines start at 4 km and go up), and a top speed of 270 km/h. This is exactly the sort of situation that favors new technology. The Tokaido Main Line was a popular intercity line in the late 1950s, but Japan National Railways couldn’t add more express trains without bumping against the capacity limit imposed by slower trains using the line; this tilted it in favor of building the Shinkansen. The Paris-Lyon main line was similarly busy in the 1970s, encouraging the construction of the LGV Sud-Est as a bypass. Nowhere in the world except Tokyo-Osaka is there a full conventional HSR line, except Paris-Lyon – but see later why it is a poor candidate for faster technology.
The main tradeoff with maglev, or even faster technology, is cost. This comes from two places. First, higher top speed requires much more advanced civil engineering, with wider curves, which means more tunnels and viaducts. Conventional HSR can limit costs by climbing steeper grades than legacy trains (the LGV Sud-Est has no tunnels, the legacy Paris-Lyon line does). Maglev can climb even faster grades, but once the speed crosses into the vactrain range, the vertical curve radius required to achieve a steep grade is so wide that it is no longer possible to vertically hug terrain the way European HSR lines do.
The second place is the urban approaches. In theory, this should be a strength of faster-than-conventional rail technology, which has a lower minimum curve radius than HSR at equal speed. But in practice, conventional HSR can leverage existing railroad lines on the urban approaches. At lower speed the stopping distances are shorter, so capacity is higher; the upper limit at speed maybe 12-15 trains per hour, but on a low-speed approach it’s closer to 24-30, so it’s possible to share tracks with legacy commuter and intercity trains.
In Japan, Spain, and Taiwan the HSR track gauge is different from the legacy gauge, so track-sharing is not possible in the major cities, driving up the cost of urban approaches. In smaller cities, Japan and Spain have gauge-change technology, which takes too much time to be of use in capacity-constrained big cities but can allow track sharing on branches. But unconventional technology cannot share tracks anywhere, requiring tunnels on urban approaches. The cost of 20 km of urban tunnel can easily match that of 200 km of at-grade greenfield HSR outside urban areas. The Chuo Shinkansen’s cost, around $200 million per km, comes from the fact that 70-80% of the line is underground, in urban areas and under mountains.
This implies that unconventional technology is most useful when there is limited benefit to be gained from track sharing. This includes the following situations:
- The cities served do not have usable legacy rail approaches, or else have a surplus of space within which to build a new approach.
- There is no need to branch and use legacy track at lower speed.
- There is no preexisting high-quality track that HSR can use, either at high speed outside cities or at medium speed on approaches.
In North America, FRA regulations traditionally led to situation #1. But FRA regulations seem to be changing, which makes track-sharing on approaches more feasible; practically every city has approaches with a surplus of passenger rail capacity (yes, even New York – Amtrak runs 4 trains per hour into Penn Station from the west at the peak, it just uses these slots poorly). In Europe, cities with poor approaches are more likely to be served on a branch, since the rest of the network is so strong. Situation #2 never applies here – branching is always useful, letting the LGV Sud-Est carry not just Paris-Lyon trains but also Paris-Marseille, Lille-Lyon, London-Lyon, Paris-Geneva, etc.
Some of the stronger intercity travel markets are in situation #3, but most aren’t. In North America, the Northeast Corridor has long stretches of high-quality track, either already capable of high speed or capable with a small number of curve modifications. That characteristic alone makes it exceptionally bad for unconventional rail technology: such technology would need a new alignment through hundreds of kilometers of suburbia in Massachusetts, Rhode Island, New Jersey, Pennsylvania, and Maryland. Toronto is also a poor candidate for unconventional technology, since it has a long stretch of suburbia in both directions with high-quality four-track commuter rail, straight enough for 200 km/h or even more. Significant suburban tracks are also useful in California (Caltrain, parts of Metrolink) and Chicago. Only the Pacific Northwest, Portland-Seattle-Vancouver, has a real shortage of usable legacy track even on the approaches. So is it a good candidate for unconventional technology? No, for reasons of distance.
The optimal distance
Faster-than-conventional rail is silly at short distance. The difference in travel time is smaller and does not justify the expense. Access and egress times are fixed, and may even go up if the station locations are less central (the Chuo Shinkansen won’t serve Tokyo Station but rather Shinagawa, a few km south of the CBD). So focusing on in-vehicle time is less useful. The Chuo Shinkansen is really at the lowest end of what is acceptable. It works because, again, the Tokaido Shinkansen is at capacity. Tokaido is also relatively circuitous in order to avoid mountains – the distance from Tokyo to Shin-Osaka is 515 km on the Tokaido Shinkansen, 438 on the Chuo Shinkansen, and 405 on a straight line. On the Northeast Corridor, the New York-Washington distance is 362 km on the railroad and 330 on a straight line, a much smaller difference.
Conversely, faster-than-conventional rail is questionable at very long distance. At maglev speed, a New York-Los Angeles train would take perhaps 12 hours, not really competitive with planes for people who don’t mind flying. At vactrain speed, the train would be competitive. However, in either case, trains require linear infrastructure, and repackaging them as a new Hyperloop doesn’t change this basic fact. Ignoring the effects of terrain, a 4,000 km vactrain or maglev line costs ten times as much as a 400 km line. This is not the case for air travel, which requires no fixed infrastructure between the airports.
There should be a good zone in the middle, say the 1,000-1,500 km range. This includes city pairs like Beijing-Shanghai, New York-Chicago, Tokyo-Sapporo, Tokyo-Fukuoka, Delhi-Mumbai, Delhi-Kolkata, and some international European pairs like Paris-Madrid. Going up to 2,000 there are also New York-Miami, Chicago-Dallas-Houston, Beijing-Guangzhou, and Los Angeles-San Francisco-Seattle; in China, where conventional HSR is faster, even 1,000-1,300 km is well within conventional HSR capabilities (Beijing-Shanghai is 1,300).
However, the fact that there is this sweet spot for unconventional rail does not mean that the construction costs are affordable. This remains a question mark. Maglev costs are either in line with HSR costs at equal tunnel proportion, or somewhat higher. The Shanghai maglev cost 10 billion RMB in 2003, which in PPP terms is maybe $100 million per km for an elevated suburban/exurban line (bad, but not terrible), and in exchange rate terms (imported technology) is somewhat more than half that. The Chuo Shinkansen seems to be $200 million per km, 70-80% underground, which is in line with urban tunneling costs in Japan but high by the standards of exurban tunneling (the 60% tunneled extension of the Tohoku Shinkansen to Shin-Aomori was $55 million per km).
The upshot is that a New York-Chicago maglev is likely to cost like 1,200 km of HSR. The western half of this line is easy – maybe a short tunnel in suburban Chicago is required, but there’s so much right-of-way space that an above-ground urban approach should be fine. The eastern half of this line consists of 600 km of pain in the Appalachians, suburban New Jersey, and a new tunnel under the Hudson. Costs approaching $100 billion are likely, and I don’t know that the benefits are commensurate.
Can you start big?
A short maglev or vactrain is of little use. Given the expense of approaches, the best use of expensive infrastructure may well be to build multiple lines using the same approach. For example, not just New York-Chicago or New York-Atlanta-Miami, but both at once, to take advantage of the same maglev tunnel under the Hudson. By itself New York-Chicago might be good enough, but it’s unclear – it’s nowhere the huge benefit/cost ratio coming from a program for conventional HSR on the Northeast Corridor at normal first-world rates.
I think this is the biggest risk with unconventional rail technology. Its basic characteristics suggest that there should be a distance range at which it works well – not too short so as to offer too little benefit versus conventional HSR, not too long so as for construction costs to grind it down. But it’s equally possible that the two bad zones, too short and too long, really overlap, so that 1,200-km lines are still too expensive to compete with planes while not offering enough speed benefit over conventional HSR to justify all this new construction.
The problem, then, is that it’s difficult to start big with a risky technology. The shortest useful maglev segment, Tokyo-Nagoya, is still well over $50 billion, and Tokyo-Osaka approaches $100 billion. This is on a route with proven demand; what about routes that don’t parallel overcrowded conventional HSR? Some government will need to take a $100 billion gamble on a long route hoping that the 1,200-km niche really exists.