If you multiply the populations of the metro areas served as a proxy for HSR ridership, then by comparison to Shinkansen lines as well as the AVE, New York-Washington traffic should be about 15-20 million passengers per year. It’s even higher if we include Madrid-Seville, an overperformer with more ridership than Madrid-Barcelona. This is just between the two metro areas, excluding additional passengers to Philadelphia. This raises two questions: what does the data suggest about modifying product-of-populations as a proxy, perhaps to account for distance? And, more importantly, is such ridership realistic for the Northeast Corridor?
First, at least on the Shinkansen and the AVE, in the range of distances up to nearly 4 hours, there’s no effect of distance on ridership, especially if we combine air and rail ridership. (We’re trying to apply this analysis to a city pair on which trains will take not much more than an hour and a half; end-to-end air traffic can be assumed to be zero.) Beyond that, Tokyo-Fukuoka air and rail ridership combined still underperforms shorter-distance links. One explanation is that as distance increases, total travel volume decreases, but rail and then air market share grows at the expense of cars and buses, and in the 1.5-4-hour range, these effects more or less cancel out. At longer distances, there is no longer much highway travel for trains and planes to poach.
With distance ignored, large cities consistently underperform small cities. This is not a surprise based on SNCF’s refined gravity model of ridership, in which travel volume is proportional not to the product of the city populations, but to the product raised to an exponent lower than 1. SNCF uses an empirically derived exponent, between 0.8 and 0.9, and AVE and Shinkansen data is indeed more consistent with that range. Some city pairs still underperform in a way that can’t be explained by population and distance, such as Tokyo-Okayama, but the exponent perfectly explains why Tokyo-Osaka underperforms a model with exponent 1.
So what about the Northeast Corridor? Current Amtrak ridership between New York and Washington is 1.74 million, but that’s just between Penn Station and Union Station. Amtrak provides its top 10 city pairs in the Northeast in its Master Plan, which include New York-Baltimore and New York-BWI, at 650,000 between them. I don’t know the ridership on more minor city pairs, such as those involving Newark or Stamford. I would guess the total including those is about 3-3.5 million; this is based just on extrapolating that of the top-10 markets on the southern half of the line just under half the ridership is between the New York and Washington metro areas, and applying a fudge factor to account for the fact that secondary markets not involving New York-Washington are less likely to make the top 10.
In contrast, based on comparison to the Shinkansen and AVE, we should expect HSR ridership of 15-20 million, about 5 times what I believe the present ridership is. (In fact, based on comparison to the lower-fare KTX, it should be if anything higher.) This is despite the fact that the current trip time is either 2:47 or 3:25 whereas with HSR it would be about 1:35. The importance of this is that we can’t expect induced demand to quintuple ridership out of halving trip time, but instead we need to explain this based on competition with cars and buses.
Part of this competition has to be about fares. Amtrak charges very high fares (see the route performance report) – on average, 28 cents per km on the Regional, and 48 on the Acela. Shinkansen fares average 23 cents per km on Tokaido, 20 on Sanyo, and 24 on the JR East network. That said, the shorter distance of New York-Washington means that absolute fares are not higher, particularly on the cheaper option. However, high fare per km does mean the trip is less competitive with cheap express buses and with driving.
This comes in addition to travel time. The Regional is an hour faster than Megabus; HSR that is three hours faster Megabus, especially if it’s also cheaper than today’s Regional, could make a serious dent in the Megabus network. Express buses already have trouble with secondary markets, because those can’t piggyback on primary markets as intermediate stops the way they can with trains. Better trains could poach the express bus market and reduce it to where it was ten years ago.
At the range of the top-performing city pairs, most people take trains rather than use roads. I do not have data for individual city pairs in Japan (but see here for Korea, where HSR overperforms, perhaps due to lower fares, which are about 15 cents per km before discounts), but at the distance of New York-Washington, 360 km, trains get a little more than half the total mode share and cars get the other half. Amtrak’s 2010 Vision says that the current rail mode share on the entire Northeast Corridor is 6%; it does not say what the share on New York-Washington is, but I’ve seen 14% elsewhere (no reference, sorry), and the Vision says that incremental Master Plan improvements will raise it to 26%. Of course going from 14% to 50% also involves induced demand, and this means the expected rise in ridership is a higher factor, potentially a factor of 5.
I’m not going to try using this method to estimate shorter-distance ridership, because then car ownership, sprawl levels, etc. become a much bigger issue, and quick-and-dirty sanity checks don’t work and are no replacement for serious ridership studies. But we can apply the method to other longer-distance portions of the Northeast Corridor. If we use the lower end of the scale, we get New York-Washington at 15 million annual passengers or a little more, New York-Boston at 15 million or a little less, Boston-Washington at 6 million, Boston-Philadelphia at 5 million.
As a secondary sanity check, the Boston-Washington air market is about 2.5 million, and for HSR to get 2.5 times as much ridership on a formerly air-dominated city pair as the pre-HSR air travel volume is the same performance Eurostar got.
All four metro areas should be interpreted as broadly as possible, to maintain comparability with Japanese metro areas, whose definition is loose and roughly comparable to the American combined statistical area. So there are just four cities on the Northeast Corridor, really. This is still not all the ridership there is – there is still New York-Philadelphia and Philadelphia-Washington, I’m just less comfortable making even an ex-recto estimate. But even without those two potentially high-ridership city pairs, we get high passenger density on all segments of the line.
Update: although I have not found city-to-city ridership data from France, I have found region-to-region numbers from Paris to the southwest. I also have some air traffic volumes from which we can deduce air/rail markets: on Paris-Nice the TGV has a 31% share of the air/rail market; on Paris-Marseille I’ve seen numbers ranging from 60% to 83%, and for this post’s purposes I’m going to assume 70%. We get air/rail traffic numbers from Paris to Marseille (5.2 million, but this grows to 9.2 million if we assume 83% TGV share and declines to 3.9 million if we assume 60%), Nice (4.2 million), Midi-Pyrenees (3.2 million), Aquitaine (5.5 million), and Poitou-Charentes (3.3 million). With the exception of the Midi-Pyrenees number, which represents a fairly long distance, all overperform the Shinkansen. Ignoring distance as always and using an exponent of 0.8, Paris-Marseille overperforms Tokyo-Sendai by a factor of 1.85, Paris-Nice by 2.21, Paris-Midi-Pyrenees by 0.77 (i.e. it underperforms), Paris-Aquitaine by 1.26, and Paris-Poitou-Charentes by 1.22. Per-kilometer fares are much lower than on Shinkansen – indeed SNCF’s total revenue, both high- and low-speed, divided just by TGV passenger-km, is €0.14 – and this can contribute to the higher traffic.
Paris-Nice can be explained as a major leisure corridor, similar to the unusually high passenger traffic to Florida or Las Vegas. But bear in mind that Nice and Marseille are metro areas and not entire regions, and under any assumption that Bordeaux and Toulouse get a greater share of the travel to Paris than the rural areas in their respective regions, they will overperform by a substantial margin. Although French metro areas are defined less loosely than Japanese ones, which can skew the Marseille and Nice numbers, the Aquitaine and Midi-Pyrenees numbers are if anything defined too loosely due to the inclusion of outright rural departments.