A post from last month on Keep Houston Houston notes how high-speed rail transformed Japanese geography to the point that it’s faster to get from Osaka to Nagano via Tokyo than direct despite a doubling of travel distance. The same comment could equally be made about rapid transit within a city: for example, for some origin-destination pairs in Vancouver, it’s faster to go the long way around the Millennium Line than to take a direct bus, and the same principle works in every other city. For both modes of transportation, this comes from high capital costs and high capacity, which make them useful primarily on the thickest travel markets, which tend to be radial around the largest center.
The next step is to look at the effect this change in transportation on economic geography. As I’ve argued before, in both cases the result reinforces preexisting centralization. This is both feedforward and feedback: a dominant city creates enough travel demand to support an HSR network and a dominant CBD creates enough demand to justify digging subways, while at the same time the quickness of travel along the rapid lines makes people emphasize connections along them and deemphasize others.
Concretely, this means that in Manhattan, with its wealth of north-south subway lines and paucity of east-west lines north of Midtown, people identify with the East Side or the West Side. Although the Upper East Side and Upper West Side are socially and demographically similar and are geographically close to each other, the social connections I’ve seen are primarily north-south. A gaming group I participate in many of whose members have recently moved to New York concentrates on the West Side since the earliest members moved to the Upper West Side, and so more people who were living or looking to live in Brooklyn or Queens are moving to Uptown Manhattan in general and the West Side specifically. The subway helps the Greater Upper West Side project influence as far north as Inwood. In contrast, the east-west connection is deemphasized to the point that people I know talk up the cultural differences between the Upper East Side and the Upper West Side, even ones who are not from either neighborhood and are not from the usual high-income demographic (though, of course, the two neighborhoods are culturally dominant and can discuss their own issues via mass media).
I do not know if the above trend is also the case for countries with developed HSR networks. However, another corollary trend is. The importance of the CBD and areas easily accessible from it is that the CBD becomes the more or less neutral choice for where people from different sectors can meet. Midtown can be easily accessed from the Greater Upper West Side, Greater Williamsburg, Greater Bed-Stuy, and so on. This effect then not only reinforces the rapid transit lines but also their nodes, to the point of creating possible centers around accidental transfer stations. In Vancouver, the Commercial Drive area functions as a major meeting location for social groups that are too widely distributed around the metro area for a place in Burnaby or along the Canada Line to be as acceptable. Although the Commercial Drive area hasn’t turned into a CBD and most likely never will, Midtown Manhattan became a CBD largely because of subway lines leading to Uptown Manhattan and Queens. Social meetings and job centers obey similar geographic rules.
In a fractal manner, in each sector there can also be a relatively neutral meeting location when the primary CBD is too expensive or too far, based on either a highway network (for example, White Plains for Westchester) or a rapid transit network (for example, Downtown Brooklyn for all of Brooklyn except Eastern Brooklyn), or even an arbitrary choice of zoning that then becomes self-reinforcing (for example, Metrotown in Burnaby). It promotes a perverse kind of equality, one in which no sector is favored over others, and the social hierarchy is based on the ease of getting to the center, in a similar manner to how in former British colonies with few whites, English sometimes arises as the politically neutral choice of language (or French in former French colonies, etc.), replacing a hierarchy between speakers of different local languages with a hierarchy between people with varying degrees of English fluency.
The exact same node effect can be observed in HSR. Japan’s become more centralized around Tokyo since the Shinkansen was built. In France and Britain there’s heavy centralization, going back many decades; from the start, the lines connecting the capital to the major secondary cities were treated as fast main lines while the others were slower branches. In South Korea, there’s mixed evidence about the role of the KTX in promoting development in secondary cities, but there has been growth in outer exurbs of Seoul that the KTX put within reasonable commute distance, such as Cheonan and Asan, even beyond the general growth of Seoul’s suburbs in the last 30 or so years. It is likely that of the secondary cities, the one emerging the best from this development is Daejeon, both the closest to Seoul and the junction of the lines to Busan/Daegu and Gwangju; for what it’s worth, even before the KTX opened, its metro area had faster population growth than the other major metro areas, excluding satellite metro areas that should really be thought of as suburbs of larger cities.
The meaning of this analogy is that an urban rapid transit network and a national HSR network will look similar. We can now extend the analogy and think in terms of connecting transportation. S-Bahn/RER-style regional rail generally involves routing preexisting commuter lines through new tunnels to provide rapid transit-style urban service; this is analogous to making HSR use legacy lines at lower speed in parts of the system that don’t justify the construction costs of a new line. Branch regional lines and buses feed people into rapid transit stations, in the same manner that legacy rail lines feed people into HSR stations. Some of the alignment questions, such as whether to tunnel or build complex viaducts to reach secondary city centers or to go around them on easier rights of way to save money, are similar, though the answers are often different (i.e. the benefits of the higher-cost alternative are much higher for rapid transit than for HSR since more people ride local transit than intercity transit, while the extra costs are comparable).
It can even explain some of the political coalitions. Rapid transit and HSR are both high-construction cost, high-capacity, long-term investments. They scale up but not down, and therefore cannot be undertaken by a cheeky entrepreneur with a moderate amount of venture capital; they are instead built by governments or very large conglomerates or sometimes both combined, and require careful planning (for example, upzoning) to ensure economic development patterns can reorient along the new infrastructure. They are also signature investments generating a lot of press, to the point that in some cases they can pursued purely for the ribbon cutting, while other forms of rail usually aren’t unless a politician is trying to oversell them as equivalent to rapid transit or HSR but cheaper.