Eurostar, the high-speed rail system connecting London and Paris, underperforms. Its ridership, 9.5 million in 2010, is very low relative to both ridership projections and the populations of the cities it connects. This is used by opponents of high-speed rail as a worst-case scenario, as evidence that high-speed rail is a lemon. In addition, Drunk Engineer has argued in comments that it comes from unique design problems such as security theater, not present on any other high-speed rail network.

I claim that it’s not Eurostar specifically that underperforms, but rather the entire London-Paris travel market, and that it’s probably due to its being an international link. Specifically, there should be fewer business ties between London and Paris than between two similarly-sized cities in the same country, or even in different countries speaking the same language. In addition, because London and Paris were traditionally separated by sea, there was never a large ground market between them for rail transportation to poach.

Exhibit #1: Eurostar’s mode share is quite normal by the standards of other HSR lines of comparable travel time. See for example figure 1 in this report on air/rail competition in Europe, with data a few years out of date, and figure 2-4 2-3 in this report on Brazilian HSR, which is more up to date.

Exhibit #2: before the Channel Tunnel opened, the total size of the London-Paris air market was 4 million per year. This is smaller than intranational links connecting smaller cities: for example, according to an EU report on the busiest single-airport pairs in Europe, Madrid-Barcelona was 4.6 million (largest in Europe) on the eve of the AVE’s opening, Paris-Toulouse and Paris-Nice were a total of 4.6 million between them, and Rome-Milan with 2.5 million. In Australia, Sydney-Melbourne has 6.8 million annual passengers, and is the fourth busiest air market in the world, after Tokyo-Sapporo (not served by HSR), Tokyo-Fukuoka (where HSR takes 5 hours), and Seoul-Jeju (Jeju is an island off of mainland South Korea).

Exhibit #3: international air links other than London-Paris underperform as well. The EU report cited above, a study by the Centre for Asia Pacific Aviation ranking all airport pairs in the world by seats flown, and a Brookings ranking of the top 100 city pairs (not airport pairs) in or into the US are all missing or underranking international city pairs with huge combined populations. Tokyo-Seoul has 21% the seats flown of Tokyo-Sapporo; Paris-Milan is three-fifths the size of Paris-Nice; the only air market from Zurich to the EU that makes the top 20 EU-to-not-EU pairs is Zurich-London, with 900,000; and New York-Toronto is not on Brookings’ list, and has only 1 million passengers per year, compared with 2.3 million for New York-Washington, which has to compete with rail, buses, and cars.

Note that this effect applies both to international pairs speaking the same language and international pairs not speaking the same language. However, language does have an effect: there are far fewer air travelers from the US to Montreal than to Toronto or Vancouver. London-Dublin is a large market (4 million) when one looks at all airport combinations. Paris-Brussels rail traffic (6 million) is lower than Paris-Lyon (18 million in 1988, the last year the LGV Sud-Est was the only LGV) but almost as high as Paris-London despite a huge city size difference. And London-New York is the largest long-haul market, more than 4 million, though much of it must be connecting traffic – perhaps the finance links between the two cities contribute.

Indeed, while Eurostar flounders with its 9.5 million passengers, domestic HSR networks thrive – follow some of the links in the above paragraph to see numbers for the TGV, the KTX, and the premium-priced AVE.

Note that this pattern applies only to intercity passenger travel. Regional travel crosses borders frequently: the S-Bahn networks of Zurich and Basel both cross borders every day, with integrated tickets and fares, and the border crossings between San Diego and Tijuana and between Detroit and Windsor are infamous for their congestion. That the travel market between New York and Toronto is small says nothing about the travel market between Buffalo and Niagara Falls, Ontario.

There are two upshots to this pattern. First, proposals for high-speed rail within the US should be compared with higher-performing lines, such as the TGV network; they should avoid comparisons to the Eurostar flop. Second, US HSR plans should give much lower priority to international links, especially to Montreal; links to Toronto, Vancouver, and Tijuana may be justifiable on grounds of regional cross-border travel.