Many people have heard that certain regions are well-suited for these projects, for example the Northeast Corridor is unusually good for HSR because it links four major cities and several medium-size ones on a single line. By implication, there has to be a flip side, i.e. regions that are poorly-suited for HSR and cities that are poorly-suited for new rapid transit. If there weren’t – if every region were like the Northeast Corridor – then the ridership models would just have higher first-order estimates. Several proposals I’ve seen in comments and on my blogroll in the last few days are in areas where the urban geography makes it harder to justify such projects. These and a few others are the examples I will use in this post.

As usual, there’s a caveat that difficult does not equal bad. Some of these ideas are worth pursuing, but have more challenges that their easier counterparts do not, and if those challenges are solved, then they can perform well. One of the biggest success stories of modern rail investment, the TGV, is in an urban geography that’s not particularly conducive to rail: France’s secondary cities surround Paris in all directions (although Lyon and Marseille are collinear with Paris), the stub-end layout of stations in Paris and many other cities forces awkward branching, Lyon needed a business district to be built from scratch around Part-Dieu. France made this work, and it’s possible some of the projects on this list can be made to work in similar vein.

High-Speed Rail in Sweden

Project: greenfield HSR lines connecting Stockholm with Sweden’s major secondary cities, Gothenburg and Malmö.

The problem: Stockholm, Gothenburg, and Malmö do not lie on a straight line. The three cities are quite small by the standards of more populated countries: Stockholm has a bit more than 2 million people, Gothenburg has a bit less than a million, Malmö has 700,000. A line connecting just two of them, or even a Y-shaped line, is unlikely to get enough ridership to justify the construction costs of full HSR. There are no large intermediate cities: the largest, Linköping, has about 100,000 people. As noted above, French urban geography is not great for HSR, either, but at least the LGV Sud-Est could serve both Lyon and Marseille, and France’s greater population ensures that its secondary cities are large enough to generate enough traffic to fill an HSR line.

As a silver lining, Malmö is adjacent to Copenhagen, and the difficult part, bridging the Øresund, has already been done. While international lines tend to underperform, the tight cultural and economic connections between the Scandinavian countries make it likely that international projects within Scandinavia would be exceptions to the rule. Copenhagen would add another 2 million people at the end of the line. However, even that is unlikely to generate enough ridership to pay for 500-odd kilometers of greenfield HSR (plus a connection to Gothenburg).

Because of its poor urban geography for conventional HSR, Sweden has investigated cheaper solutions, allowing higher speeds on legacy track or on greenfield tracks built to lower standards. As a result, there is research into the possibility of high-speed tilting trains, running faster than the 250 km/h Pendolino. This research is likely to be useful in the UK and US, where the urban geography is better-suited for HSR but fully greenfield construction is obstructed by suburban development near the rights-of-way and by high construction costs, but the original context was faster speeds within Sweden.

High-Speed Rail in the Pacific Northwest

Project: greenfield HSR connecting Portland, Seattle, and Vancouver. This is not officially proposed anywhere that I know; current plans focus on incremental improvements to the Amtrak Cascades. However, every American HSR fantasy map I’ve seen (including the ones I’ve drawn) includes this link, since at least superficially based on city populations it would succeed.

The problem: getting out of the major cities involves a slog on curvy legacy track in areas where it’s hard to straighten the right-of-way. Heading north of Seattle, the route goes along the water, in terrain that is too hilly for an easy inland cutoff all the way to Everett, 50 km north. Getting out of Vancouver is also hard, because of suburban development in Surrey, and becomes even harder if one wants the Vancouver station to be Waterfront rather than Amtrak’s current stop, the less centrally located Pacific Central. The Northeast Corridor is said to have slowdowns near the major stations, leading to proposals to bypass them with new tunnels, but at no point are there 50 nearly-continuous km of low curve radii; the New Haven Line does not look as curvy, while the Shore Line farther east is easy to bypass on I-95.

The Seattle-Portland segment is much easier: the route heading south of Seattle is not constrained, and north of Portland it is possible to run alongside I-5. However, the most important intermediate cities, Tacoma and Olympia, can only be served with exurban stations, since getting into their centers would require the mainline to detour on curvy alignments.

Through-Run Commuter Rail in Chicago

Project: there are many proposals by transit activists to construct new infrastructure to enable through-running on Metra, analogous to Crossrail, SEPTA Regional Rail, the Paris RER, and multiple S-Bahns. Details differ, but other than the lines through Union Station, through-running generally means connecting Metra Electric to some of the lines feeding into Union Station from the north or the Union Pacific lines; UP-North is especially notable for serving dense neighborhoods and not having any freight traffic.

The problem: the layout of the lines entering the Chicago central business district makes it hard to build a coherent network. What I mean by coherent is that commuter lines can make multiple CBD stops to serve different CBDs, or different parts of the same CBD: in New York, a Penn Station-Grand Central connection would let trains serve both the West Side and the East Side. Look at the map proposed by Sandy Johnston, in the second link above: there is no station on the Near North Side, there is no connection from the West Loop stations to the Loop, and effectively lines are still going to be split between lines bound for the West Loop and lines bound for the Loop in the through-run system.

None of this is the fault of any of the people drawing these maps. To serve both the West Loop and the Loop, a line would have to go east-west in the vicinity of Union Station, where there is no legacy line pointing in the right direction. The options boil down to a long greenfield east-west subway, and an awkward transition to the preexisting east-west lines, BNSF (which is too far south) and UP-West (which is too far north), which to add another complication carry heavy freight traffic.

A system prioritizing north-south connections runs into different dilemmas, concerning the tradeoff between service to the Near North Side and easier connections to the rest of the North Side Metra lines. A north-south line connecting UP-North to Metra Electric through the Near North Side would be beautiful, and miss all other Metra lines and most L lines. Sandy’s proposal has Metra Electric swerving west to meet UP-North just north of its terminus at Ogilvie Transportation Center, meeting all L lines and potentially the North Side Metra lines but missing the job centers in the West Loop and Near North Side.

Rail to LaGuardia

Project: construct some rail extension to LaGuardia Airport. Which rail extension varies based on the proposal. The most mainstream proposal, in the sense that it was supported by Giuliani until it was torpedoed by neighborhood opposition, would have extended the Astoria Line east to airport grounds. More recent proposals from various activists have included not just the Astoria Line extension, but also a Northeast Corridor spur, an AirTrain from the Astoria Line, an AirTrain from Jamaica with JFK connections, a subway shuttle under Junction, and a subway running from the airport to 125th Street along the route of the M60 bus.

The problem: all of the above ideas face the same pair of problems. At the airport end, the airport competes with other urban destinations, rather than complementing them by lying on the same straight line with them. An extension from the west, such as the Astoria Line extension, needs to choose between serving the airport and serving the Astoria Boulevard corridor, which has high residential density and no nearby subway service; Astoria Boulevard itself is so wide that as with Queens Boulevard, an elevated line in its middle would be an improvement. Farther east, there is nothing that a LaGuardia extension could be continued to, because of Flushing Bay. An extension across the bay going to Flushing or College Point could be useful, but an extension of the 7 to College Point would be even more useful and avoid underwater tunneling. The bay, and more generally the Long Island Sound, dooms any proposal for a loop returning to the mainline, in the manner of Zurich Airport, while a spur would again compete for capacity with more important lines. Compare this with LAX, which, going along the Harbor Subdivision, is collinear with Inglewood, the Slauson corridor, and Union Station, and would have an easy connection to El Segundo.

At the other end, the question with every airport extension is, what does it connect the airport to? The answer for LaGuardia has to be the Upper East Side, where as I remember most riders originate; but there is no good way of connecting to the Upper East Side, which has no east-west subway line, and shouldn’t, as there are perhaps a hundred kilometers of higher-priority tunnels in the region. A connection to 125th Street is ruled out by the fact that Second Avenue Subway has an even better connection to 125th. The Astoria Line serves the Midtown hotel cluster well, and has a connection to the Lexington trains to the Upper East Side, but I doubt that it can beat a taxi across the bridge in non-rush-hour traffic.

Providence East Side Tunnel

Project: restore rail service through the East Side Rail Tunnel, with a new connection to Downcity at the western end and connections to new or restored rail lines in and beyond East Providence. In Jef Nickerson’s version, the trains are light rail and drop to the surface at the Downcity end. In mine, they continue elevated through Downcity, with a new station replacing Providence Station for both commuter and intercity rail. All versions include a stop at Thayer Street for Brown University service, should one be constructable at reasonable cost.

The problem: there’s no real need for local or regional service from the east along the tunnel (intercity service could be sped up by about half a minute to a minute by avoiding curves in Pawtucket). Light rail service would run into the problem of incredibly spread-out suburbanization east of Providence. Commuter rail would run into separate problems: the legacy lines go along the water in East Providence and don’t serve the town itself well; beyond East Providence, the line going north serves the same suburbs as the existing Providence Line minus Pawtucket, while the line going south would need extensive and costly restoration work to get to Fall River, and only passes through small and low-density intermediate points.

Cutting off Providence Station to move the city’s main station to the south is useful, but the only rail from Providence to Pawtucket and Woonsocket goes due north of Downcity and would be left out of this system. Shoehorning it to the same station that leads to the East Side Tunnel would produce every adverse impact of viaducts on cities: heavy visual impact coming from elevated-over-elevated grade separation, squeal coming from low curve radii, takings of condo buildings near the existing Providence Station.