Sometimes, Half a Line is as Good as No Line

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.


  1. Zmapper

    The explanation given for Colorado HSR serving the airport but not Downtown Denver was that according to their models, the airport was projected to have twice the ridership.

    Draw your own inferences as to the validity of the model CDOT uses…

      • Adirondacker12800

        A few minutes with Google satellite views and there a four lane boulevard going into the airport and nothing else that normal people would use. From the north heading towards downtown Denver there’s two lanes of I-70, five lanes of I-25 and three lanes of US36. Where do people want to go?

  2. betamagellan

    Colorado also has a history of looking into maglev for small markets—the idea of maglev ski trains to Vail and the like has been kicked around for over a decade.

    I’ll have to admit to wondering about something like Chuo Shinkansen for the NEC—if Amtrak wants to spend Chuo Sinkansen levels anyway, after all…(of course, capital costs for maglev would likely balloon in the same way, and it’s easier to scale back a bad rail proposal that can link up with the existing network)

  3. letsgola

    This is the essential problem in trying to implement quality transit in highly car-dependent cities: you need a big enough initial network to make it useful, but it’s hard to get people to invest that much at the outset. Ironically, once the thing is successful and people are willing to put more money in, it’s easy to make small extensions pencil out.

    As far as Colorado HSR goes, I can’t believe that any scenario makes sense. Fort Collins, Colorado Springs, and Pueblo are only worthy of that level of investment if your perspective of density and cities has been warped by living at the intersection of vast, sparsely populated plains and vast, sparsely populated mountains. Colorado has barely half the population of LA County, but it seems like a lot next to Wyoming, Nebraska, the OK & TX panhandles, New Mexico, etc. Given how small those cities are, and the low probability that either end of your trip is at the HSR station, regular speed rail is just fine.

    Looking further, there’s just nothing near Denver that’s in HSR’s sweet spot for distance. Phoenix and Las Vegas are 600 miles away over some of the most topographically tortuous, least populated parts of the country. Oklahoma City is 500 miles, Dallas is almost 700 miles. Albequerque is 300 miles & El Paso is 500 miles, each with metro populations of 1 million. Probably the best you could do is Salt Lake City, which is still 350 miles, and there’s a reason the UP went up the Platte River to South Pass, Wyoming…

    • Alon Levy

      Yeah, under any reasonable scenario, Denver and Salt Lake City are going to be the last major cities in the US to have any HSR connection. There’s a good chance they should never get any conventional HSR. Adirondacker likes to point out that Denver is farther away from Chicago than New York, Boston, Dallas, New Orleans, and Atlanta. The nearest city to Denver that’s larger than Denver is Dallas, which is still outside conventional HSR range, with no medium-size cities in between. This is where the low density of the US really comes into play – it has subregions of high enough density that metro areas are close enough together to justify HSR, but in between it doesn’t have anything to justify the investment.

      The city size issue is certainly there – as in the tweet you posted a few weeks back laughing at proposals to center HSR on Pittsfield, Massachusetts – but the geography of Colorado is terrible for HSR independently of it. If the Denver, Fort Collins, Colorado Springs, and Pueblo metro areas were each five times bigger, the corridor would still be questionable as an HSR route, although as a medium-speed intercity rail link it would be very strong.

      • Adirondacker12800

        here’s some things to contemplate
        The population of Wyoming, Colorado and New Mexico is 7,652,002. Thats the four boroughs of New York City, Staten Island can cut it’s moorings and float away to Xanadu.

        Or the population of the DC-Baltmore CSA is 9,331,587. The DC MSA is a paltry 5,860,342. Or a Staten Island’s worth bigger than Colorado. More Denver to the East Coast and it’s jockeying with Hartford for 6th position as the biggest metro area after NY, DC, Philadelphia, Boston and Baltimore. Bigger if you only consider Hartford. Smaller if you merge Springfield and Hartford into one CSA.

        It’s just under 600 miles from Laramie to Albuquerque. Or just over 600 from DC to Atlanta. There’s 5,268,860 people in Atlanta’s CSA. How ’bout Chicago-Memphis via Saint Louis?
        Or just over 600 miles from Cleveland to Boston and just a bit shorter to New York via Albany. 650 from Portland Maine to Richmond Virginia. East of the Mississippi it’s hard to get a corridor that’s 600 miles long and doesn’t have a whole string of large metro areas on it. Sorry Fort Colling but there’s, in nice round numbers, twice as many people in New Castle County Delaware than in your metro area. Or two and half as many in metro Akron.

        • Eric

          Unlike much of the US, in recent years the Denver area HAS demonstrated the ability to get (urban) public transportation projects finished. So “it should logically work better in other places than in Denver, but didn’t work in those places” is not a sufficient counter-argument.

          • Alon Levy

            Only up to a point. Just as Denver shouldn’t be building anything like SAS (yet), Colorado shouldn’t be building HSR.

          • Adirondacker12800

            I doubt it ever will. Unless the population of the US is 2 billion.

          • Eric

            “Unless the population of the US is 2 billion.”

            Or they discover tons of oil in Colorado

          • Alon Levy

            Alberta already has tons of oil, and is rich and has high population growth, but that’s not supporting any sufficiently large city. Calgary and Edmonton are growing quickly, but are still small cities, no matter how much oil the province is sitting on.

          • Adirondacker12800

            There are tons of oil in Colorado, They’ve known about it since someone decided to use some of that black shale for a fireplace and it burnt down. And even if they figure out a way to make that into liquid petroleum it’s not going to turn Denver into Manhattan, Or even Philadelphia.

      • Nathanael

        ” the corridor would still be questionable as an HSR route, although as a medium-speed intercity rail link it would be very strong.”

        Every previous proposal for Colorado “HSR” has meant something like Michigan “HSR”, i.e. reliable medium-speed intercity rail.

        This latest proposal from CDOT, however, seems more like a joke designed to prevent anything from getting done.

  4. Adirondacker12800

    The half-done job is. In a trivial sense it’s obvious that half a tunnel across a mountain is useless.

    … well if it’s a two bore tunnel pair and they build one tunnel first it would be useful. Not very, but useful…

    • Alon Levy

      Yeah, that’s certainly true. But if it’s a single-bore tunnel and you’ve only built half of it… or if you’re only building a tunnel halfway, to the great metropolis of Palmdale, and calling it an initial operating segment…

      • Nathanael

        Your latter example isn’t that bad because it’s possible to continue trains to LA, albeit over a slower route… breaking connectivity is the absolute worst thing you can do.

        For some dramatic examples of half-building, look at Cincinnati. The most famous so far is the Cincinnati Subway, of course, which managed to end just far enough away from downtown that it wasn’t useful unless more was built.

        But there’s also a large railroad tunnel which was literally dug three quarters of the way through a hill and abandoned before completion; ran across that reading about the city.

        And now, of course, it looks like they’re likely to abandon the streetcar after spending most of the money, relocating all the utilities, and actually laying a bunch of the tracks — it’s going to cost about as much to shut it down as it would to finish it (, and if the streetcar is cancelled a major foundation will pull out of all the projects it funds in the city ( ), but because the new mayor and his pals are jackasses, they’re going to do it anyway.

        Of course, it’s also worth looking in NY at the Second Avenue Subway, where a disconnected collection of tunnels were built in the 1970s and never connected to anything, making them entirely useless until very recently. But at least there was an external and unexpected cause there, rather than just jackassery as in Cincy.

        I may be rather literal-minded here, but it’s startling how many examples I can come up with which are *really* half a line, and as a result, completely useless. What’s really impressive is how many of them are in Cincinnati.

        • Ian Mitchell

          I used to think people in the rural south were myopic, racist, and niggardly when it came to non-road public project.

          Cincinnati showed me that, comparatively, those folks are forward-looking, colorblind, and chrematistic. The city has had race riots in the 21st century.
          That’s how bad their policies are.

  5. Adirondacker12800

    The [Hyperloop] technology is feasible.

    In Microsoft Train Simulator. In the real world I don’t know.

    Passengers tend to splatter when they crash into the wall only a few centimeters away at 1000 kilometers an hour. Or into the cushion of sea level pressure air that just leaked into the tube. It looks good on paper but what kind of safety systems are going to make it possible? Solving all the other problems are academic until you crack that nut. Intercontinental vactrains have the same problem. It’s not going to be pretty when delicate human beings decelerate that abruptly.

    Train crashes into the side of a conventional tunnel it it scrapes the dirt off the wall and it can be back in service reasonably fast. Train crashes into the lightweight tube how many kilometers of tube zip open like a kipper can? If the interior of the conventional tunnel is bit lumpier after the crash it’s a bit noisier until they can get around to spraying some gunite if they get around to it all. How perfect does the interior have to be to have a supersonic train passing it centimeters away… The wall centimeters away from the vehicle is the first problem to solve.

    • Stephen

      The Shinkansen has never crashed in 50 years of service, and has proven that if your service is reliable enough, you don’t need any survivability at all. (My understand is that the vehicles have essentially no protection if they crash – no crash energy management, no bulk strength, no nothing.)

      • Adirondacker12800

        Shinkansen don’t depend on a complex air evacuation system to operate properly. Or have obstructions centimeters away from the fast moving trains.

        • Andre Lot

          Rudder and elevator systems on airplanes are much more fragile and serious in terms of having a failure cause catastrophic damage, yet planes fly at the thousands every day.

          • Joey

            Yes, but planes don’t have to maintain their path to within fractions of a millimeter.

          • Adirondacker12800

            Or when they shed a part or suffer a sudden pressure drop it doesn’t make the following plane crash. ( which has happened but it’s even rarer than plane crashes in general )

  6. Steve Dunham

    One obvious (to me) extension is the Heartland Flyer from Fort Worth to Dallas. Dallas is the far bigger market and only another 30 miles. Maybe it requires a backup move or a crew change. It should still be done. The Amtrak timetable merely gives contact information for Trinity Railway Express and advises passengers to get their own information about a connection.

    Off topic: Did you see that Passenger Train Journal this fall had articles about rails in Israel and Jerusalem’s light rail system?

    • Alon Levy

      I haven’t seen it, no. (Within Israel, the railroad is unpopular due to accidents and low speeds outside the Tel Aviv-Haifa trunk line; and Jerusalem’s light rail is also unpopular because of construction disruption, cost overruns, and service to settlements, even though the trains are well-patronized.)

      Yes, the Heartland Flyer to Dallas would be a major boost. At the very least, Amtrak could offer through-ticketing with TRE and coordinate schedules, if for some reason it’s impossible for Amtrak itself to run through.

  7. Nathanael

    Regarding HS2, it has a second purpose, which is congestion relief: the existing lines are very crowded. This has actually been the trump card whenever anyone tries to cancel the project.

    This also provides some insight into why it’s so expensive; basically the whole damn route is one conurbation by the standards of much of the world. England is a *very* heavily built-up country, and the un-built-up parts are treated as parks and preserves, not “empty land”. Germany has some similar issues in their densest conurbations.

    Regarding your main point, I think the most famous example of “half a line” in recent years is Northstar from Minneapolis to… uh… Big Lake. It was supposed to be from Minneapolis to St. Cloud, and I still think that that route would actually have been pretty decent — but instead, it is literally half a line.

    • Alon Levy

      England is dense, but so are the Netherlands and Belgium. All three have 400 people per km^2, give or take. England doesn’t have the sprawl levels of the US; almost immediately after you get out of Greater London, heading northwest, you get into farms dotted by the sporadic suburb; like in France and unlike in California, those farms are irregularly shaped, so the farmers should be amenable to land swap deals. The initial plans had tunnel length in the single-digit percent, if I remember correctly, and the topography of the route suggests that bridging can also be minimal. Instead, they’re tunneling 16% of the route and putting another 40% in open cuts because NIMBYs (link). Unlike in California, they can’t just stick a fork in one segment with asshole residents and build elsewhere, because the asshole residents live near the critical part of the line heading into London.

      • Nathanael

        Ah, but you see, this was my point when I said that the un-built-up parts are treated as parks and preserves, not “empty land”.

        What you see as “farms” with irregular shapes, the English see as valuable historical preservation of ancient land use patterns. :eyeroll: That’s where the NIMBYs showed up *and the city people backed them*. These farms are, effectively, *tourist attractions*.

        “Unlike in California, they can’t just stick a fork in one segment with asshole residents and build elsewhere, because the asshole residents live near the critical part of the line heading into London.”
        Now you begin to get it.

  8. Nathanael

    “Sometimes, starting small means failing….”

    I think the Daniel Burnham quote is appropriate here.
    “Make no little plans. They have no magic to stir men’s blood and probably will not themselves be realized.”

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