The perfect is not the enemy of the good when it comes to rail projects. The half-done job is. In a trivial sense it’s obvious that half a tunnel across a mountain is useless. But even partial lines that have some uses are sometimes so much less useful than the full line, that the economic benefits of completing the half line to the full system are actually greater than those of building the first half. In many cases, even partial lines that are very good on their own have relatively easy extensions with very good economics.
This is primarily true for intercity rail, since costs are roughly proportional to route-km whereas benefits (e.g. high-speed rail operating profits) are proportional to passenger-km: once a first-phase rail line is in place, any future phase such that passengers will use the first phase for much of their travel will generate a large amount of passenger traffic relative to infrastructure construction. Probably the simplest example of this is extending California HSR to Sacramento: once a Los Angeles-San Francisco system is in place, especially if the route goes over Altamont Pass, extending to Sacramento requires only about 100 km of additional construction (180 if the LA-SF route is via the currently planned Pacheco Pass route), in flat land, but people would be taking the train from Sacramento to Los Angeles, a distance of about 600 km. Thus, despite generating much lower ridership than San Francisco, Sacramento is a highly beneficial extension of California HSR, once the LA-SF first phase is in place.
There are several more places in North America that are like this. When I tried applying a very primitive ridership model to American city pairs, what I found is that next to the Northeast Corridor, the highest-performing lines are extensions of the Northeast Corridor to the south. This is for the same reason as with Sacramento: once Boston-New York-Washington is in place, an extension to Richmond would generate 540 passenger-km of New York-Richmond travel on just 180 route-km of Washington-Richmond HSR, and thence extensions to Raleigh and Norfolk would be similarly high-performing, and so on. Some of those extensions would add about 40 million passenger-km per route-km of new construction, compared with about 28 million on the Northeast Corridor alone; in other words, assuming constant per-km cost, the rate of return on some of the extensions is higher than on the Northeast Corridor trunk. Similarly, although international HSR links are overrated, once New York-Buffalo is in place, an extension into Toronto becomes high-performing (with about 30 million passenger-km per new route-km after a fudge factor accounting for the underperformance of international city pairs), which is especially useful given that New York-Buffalo’s projected traffic based on said primitive model is marginal.
In those cases, the picture is bright, in that the first phase is strong on its own, and then future phases become natural extensions, which can be funded on the heels of the first phase’s success.Unfortunately, in many cases the situation is different, and the first phase is really a half-built line that isn’t much better than nothing, at least on the proposed merits. For example, High Speed 2’s rising costs are causing the cost-benefit analysis to head well into marginal territory: as per PDF-page 15 of a Parliamentary primer, the benefit-cost ratio of the first phase, London-Birmingham, is now down to 1.4, while this of the full system as proposed by the Cameron administration, going to Manchester and Leeds, is 1.8. Although 1.4 > 1, common practice in Europe is to build only projects with benefit-cost ratios higher than 1.2 or 1.3, because of the risk of further cost escalations (although the stated cost includes a generous contingency factor). The environmental benefits are likewise lopsided in favor of full construction, according to pro-HSR group Greengauge 21: three quarters of the benefits come from the second phase. This is because few people fly from London to Birmingham or Manchester already, since the existing medium-speed trains are fast enough at these distances to outcompete low-cost flights; however, there’s a large volume of people flying from London to Glasgow, and it is expected to take the full opening of HS2 to get enough of those fliers to switch to make a significant difference.
In this case, HS2’s first phase is better than nothing, and the problem stems from extremely high costs: without contingency, London-Birmingham, a distance of about 180 km, is projected to be about $23 billion after PPP conversion, which at nearly $130 million per km is worse than California HSR, which has to tunnel under tall mountain ranges. With contingency, it is $175 million per km, not much less than the projected cost of the majority-underground Chuo Shinkansen maglev. If the costs were brought down to reasonable levels, the first phase alone would be highly beneficial, as can only be expected given the size of London and the secondary cities of the West Coast Main Line.
In some other proposed cases, even the benefits are marginal. Worse, sometimes attempts to cut costs lead to steeper cuts in benefits. The example that motivated this post is a recent story of a proposal for HSR in Colorado, which is not planned to serve the built-up area of Denver at all, but instead stop at the airport. An airport stop without a downtown stop is unacceptable anywhere, especially given Denver’s airport’s large distance from downtown (30 km, vs. 15 km in Shanghai, where most HSR trains stop at the domestic airport and only a few stop downtown at Shanghai Station). It is especially unacceptable given that Denver is to be connected to cities that are within easy driving or medium-speed rail distance: Fort Collins is 100 km north of Denver, Colorado Springs is 110 km south, and Pueblo, which is only proposed as part of a larger second phase together with a Rocky Mountain crossing, is 180 km south. At the distances of Fort Collins and Colorado Springs, the egress time would eat all time advantage of HSR over driving; at the distance of Pueblo, it would eat most of the time advantage. Saving money is nice, but not when it makes the entire project useless except to the occasional Fort Collins- or Colorado Springs-based flier.
One can go further and ask why even build HSR at such short distances. On the Northeast Corridor, full-service HSR is a great investment, because of the combination of extremely thick city pairs at the 360 km mark (New York-Washington and New York-Boston) and one reasonably thick pair at the 720 km mark (Boston-Washington), which is too far for medium-speed rail to compete with air. Philadelphia’s presence boosts the case for HSR – it conveniently provides a source of reverse-peak traffic away from New York and Washington, adds long-distance travelers to Boston, and adds short-distance high-speed travelers to New York – but by itself it’s not worth it to build HSR at the distance of New York-Philadelphia. If Boston and Washington weren’t there, then incremental upgrades with a top speed of 200 km/h or maybe 250 km/h would be best, and higher speeds would just waste money on more expensive trains and create noise pollution and higher energy consumption.
The same analysis is true of faster-than-HSR travel modes. The other motivation for this post, in addition to Colorado’s proposal, is Japan’s attempt to export maglev to the US, proposing the Northeast Corridor as the route to run maglev on, with Baltimore-Washington as the first segment, which Japan proposed to build for free, as a loss leader. Nobody needs maglev from Baltimore to Washington: the egress time is going to ensure the benefits of maglev speeds over HSR speeds are small, and even the benefits of HSR speeds over fast commuter rail speeds are limited. The Chuo Shinkansen is only planned to be about 440 km long, but it’s a capacity boost on a line that already has HSR with extremely high ridership, and not just a speed upgrade. Elsewhere, Japan builds conventional HSR rather than maglev, even for inter-island travel, where people fly today since the Shinkansen takes 5+ hours and flying takes an hour.
Part of my distaste for Hyperloop essentially comes from the same problem: it tries to compete with HSR at a distance where HSR is appropriate and faster trains are not. All of the technical problems of Hyperloop – thermal expansion, claustrophobic vehicles, extreme levels of lateral acceleration – are solvable, at the cost of more money. The technology is feasible; it’s Musk’s order-of-magnitude-too-low cost estimate that I object to. The problem is that at LA-SF distance, access and egress time and security will eat the entire time advantage over conventional HSR, in similar vein to the problem with siting Denver’s HSR station at the airport. Conventional HSR still involves regular trains that can run on electrified legacy lines, so it’s cheap to go the first and last miles within the Bay Area and the LA Basin; maglev doesn’t have this ability and neither do vactrains. Thus there will always be the problem with the first and last mile, which can be solved only by spending even more money – even in the case of the Chuo Shinkansen, JR Central decided that Shinagawa, just outside Central Tokyo, is good enough, and there’s no need to spend further money to get trains into Tokyo Station. But the access, egress, and security time penalties are constant, whereas the time advantage over slower modes of transportation grows with distance.
So by all means, let’s think about maglev from New York to Chicago and Miami and from Los Angeles to Seattle, where HSR is too slow to compete with air travel; let’s think about a vactrain at transcontinental scales, were open-air maglev is too slow. There’s a reason this year’s April Fool’s post emphasized that the vactrain system should be intercontinental and globally connected. I don’t think maglev in the US or a vactrain anywhere pans out in the next few decades, but at least at this greater scale they wouldn’t be crowding out a technology that can succeed, i.e. conventional HSR at the scale of the Northeast Corridor or California.
Sometimes, starting small means failing. A strong first phase with stronger second phases, such as LA-SF or Boston-NY-DC, is likely to become a success and motivate the political system to spend additional money, partly from first-phase profits, on extensions. A weak first phase that needs additional phases to pan out won’t lead to the same extensions. When a white elephant project opens, nobody listens to critics who say it should’ve been built bigger, even in the uncommon cases when those critics are right. Colorado HSR as proposed is going to get faltering ridership, not enough to justify the cost, and cause widespread disaffection even with potentially strong rail projects in Colorado. The same is true of any faster-than-HSR project that tries to replace HSR instead of capitalize on its strength in serving much longer-distance city pairs. If Musk succeeds in causing the median Californian to turn away from HSR and build Hyperloop instead, then first Hyperloop will turn out to cost ten or more times as much as Musk predicted (for which people won’t blame Musk but the government – Musk’s sycophants will tsk-tsk from the sideline and say that if only he had been in charge), and second the ridership won’t cover the costs, leading people to decide that any linear transportation corridor is bad and the government should stick to highways and airports.