The most interesting transit planner in the world:

This principle is true primarily for large international airports. As I will explain, this is less true of smaller airports. But before going on, I would like to clarify a distinction between bad and overrated. Airport connectors, as I have argued many times, are overrated: city elites tend to like them disproportionately to their transit usage, as do many urban boosters, who think a comfortable airport connector is a necessary feature of a great global city. The result of this thinking (and also the main evidence we have that this thinking exists) is that airport connectors are built at much higher costs per rider than other transit projects: the JFK and Newark AirTrains cost more than $100,000 per weekday rider, much more than other recent rail projects in New York; even the far over-budget East Side Access, at current estimates, is about $60,000.

However, overrated does not mean bad. There exist airport connector projects with reasonable cost per rider. They’re still overrated, which means they’ll be built concurrently with even more cost-effective non-airport projects, but they’re good enough by themselves. As an example, take the Canada Line. The total cost was about $2 billion, and the latest ridership figure I have, from 2011, is 136,000 per weekday, ahead of projections. At $15,000 per rider, this is reasonable by European standards and very good by North American ones. Let us now look at the two branches of the line, to Richmond and the airport. Lacking separate cost data for them, I am going to estimate them at about $300 million each, as they are entirely above-ground; the airport branch is 4 km and the Richmond branch is 3 km, but the Richmond branch has an urban el and the airport branch doesn’t. For ridership data, we have this set of figures per station (which results in a Canada Line total of only 113,000). Boardings and alightings sum to 19,000 on the airport branch and 34,000 on the Richmond branch; we’re double counting intra-branch trips, but there presumably are very few of these. As we see, the Richmond branch is more cost-effective, but the airport branch holds its own – since the per-station data has a lower overall Canada Line ridership, the airport branch’s presumed cost per extra rider generated is less than that of the entire line! (This sometimes happens, even with branches that generate less ridership than the trunk.) Clearly, despite the fact that airport connectors are overrated, this is an example of a good project.

The importance of the overrated vs. bad distinction is then that good transit advocates need to be wary, since airport connectors that don’t work well might get funded anyway, ahead of more deserving projects. But there remain good airport connectors, and therefore we should discuss what features they might have. The answer given by city elites is typically “nonstop connection to the CBD,” often with a premium fare. But the good transit answer is more complicated, and the graphic at the top of the post is only a partial answer.

There is a difference between short- and long-distance air travel. In many cities it doesn’t matter much because there’s a single dominant airport – Beijing, Frankfurt, Zurich, Atlanta, Toronto – but in others there are multiple airports, with different roles. Often there will be a smaller, closer-in, older airport, serving mostly domestic flights, and a larger, farther away, newer international airport. Paris has Orly and Charles-de-Gaulle, Chicago has Midway and O’Hare, New York has LaGuardia and JFK (Newark is intermediate in its role, even if it’s the oldest), Los Angeles has Burbank and LAX (the other airports are somewhat outside this division), Dallas has Love Field and DFW, Tokyo has Haneda and Narita, Seoul has Gimpo and Incheon. Because those airports have different functions, they require different kinds of transportation links.

First, let us consider departing passengers. If they travel to another continent, their options are quite restricted: for example, if they live within driving distance of Atlanta, they’re flying out of Atlanta. Even if there are closer secondary airports (such as Greenville-Spartanburg and Chattanooga), they don’t offer such service – at most, they offer a connecting puddle jumper flight to the primary airport. In contrast, if they travel shorter distances, and live far from the primary airport, they could fly out of a secondary airport, or might just drive instead of flying: a 2-hour drive to the airport is comparatively more tolerable for an 8-hour intercontinental flight than for a 1.5-hour short-hop flight. For example, when I lived in Providence, my air trips were all to the West Coast or Europe, so I flew out of Boston or even New York; but when my sister visited, she chained trips and also visited her boyfriend, who at the time lived in North Carolina, and for the domestic leg of the trip she flew out of T. F. Green.

The result is that primary international airports draw their departing passengers from a much wider shed than mainly domestic airports. In metro areas with such separation of airports, the international airports – Charles de Gaulle, JFK, DFW, Incheon, etc. – draw riders from faraway suburbs and even from adjacent small metro areas, whereas the domestic airports draw riders primarily from the city and its nearby suburbs.

Now, let us consider arriving passengers. Destinations are more centralized than origins, but this is especially true for international trips than for domestic ones. Tourism trips are heavily centralized around a few attractions, which in most cities are in the CBD, or in specific locations: if you’re flying to the Paris region for tourism, your destination is either Paris proper or Eurodisney, rather than an average suburb. Business trips are also heavily centralized around the CBD and a few edge cities. Personal visits have no such concentration, and these are much more common for short-distance domestic flights than for long-distance international flights. I am unusual in that I live on a different continent from my parents; usually, people live within ground transportation or short-distance flying distance from family and friends, depending on the country they live in (short-distance flying distance is more common in the US). The result here is that arriving passengers at domestic airports are typically interested in visiting the CBD but often also the rest of the metro area, whereas arriving passengers at international airports are much more CBD- or tourist attraction-centric.

Some evidence for this difference can be found in looking at the Consumer Airfare Report, which has domestic O&D traffic counts between airport pairs. The primary international airport usually has a smaller percentage of its domestic O&D traffic going to shorter-distance cities. For example, at LAX, 13% of traffic is within California, and another 6% is to Las Vegas, Phoenix, and Tucson, within a 3-hour high-speed rail range. At Burbank, the corresponding figures are 42% and 21% respectively. The same pattern can be observed for O’Hare (8.6% of traffic is internal to the Midwest) and Midway (14.6%), and DFW (3% of traffic is internal to the Texas Triangle) and Love Field (27%).

The mode of transportation that best suits the needs of international airports is then mainline rail. On the one hand, it tends to be better than urban transit at serving trips that are dedicated to CBD service, since commuter rail is more radial than urban transit, and the stop spacing is typically also longer (although dedicated premium connectors are still often wastes of money). On the other hand, it can extend deep into the suburbs and to adjacent metro areas, and expand the airport’s draw. People can ride intercity (often high-speed) trains direct to the terminal at Frankfurt, Zurich, and Charles-de-Gaulle, and this allows those airports to be the primary international airports for metro areas in a wide radius: SNCF code-shares with airlines to connect people from Charles-de-Gaulle to Lyon, 400 km and 2 hours away by TGV.

This is not true of small domestic airports. A TGV connection to Orly would’ve been much less beneficial than the current connection to Charles-de-Gaulle: most of Orly’s traffic is short-distance, often competing with the TGV rather than complementing it.

With this distinction in mind, we should look at the situation at the major American airports. In California, the current plan is to have California High-Speed Rail serve both SFO (at Millbrae) and Burbank Airport; the original plan served Downtown Burbank instead of the airport, but the HSR Authority seems to have shifted its focus, and wants Burbank to be the southern terminus of the line, pending construction to LA Union Station. This is bad planning. Nearly two-thirds of Burbank’s traffic competes either with California HSR or with future tie-ins. People from Bakersfield and Fresno are unlikely to take a train to the airport to connect to a flight, since they can take a train the whole way, or drive directly to Las Vegas or Phoenix. People in Bakersfield and Fresno would be more interested in a connection to LAX, whose traffic complements rather than competes with intercity rail.

Los Angeles could build a connection to LAX, running both frequent electric commuter trains and high-speed trains on it. The Harbor Subdivision has existing tracks from Union Station almost the entire way to the airport, although the route is at-grade, with a large portion of it running next to Slauson Avenue, and most likely a major project like this would require viaducts. Only a short greenfield segment, elevated over Century, is required to reach the proposed Terminal 0 location, and that is only necessary if, as in Zurich and Frankfurt, LAX wishes to avoid a landside people mover. It is both bad transit and bad politics to build this only for nonstop trains: the route passes through reasonably dense urban neighborhoods, and should have 10-12 stops along the way, with some trains running local and others making only 1-3 stops, at major nodes such as Inglewood or the intersection with the Blue Line. There is room for passing sidings at the line’s midpoint, but the low top speed and the short length of the line is such that overtakes are only necessary if there are nonstop and local trains every 10 minutes. Such an airport connector would serve many different trips at once: HSR trips from Central Valley cities to LAX, arriving trips from LAX to Downtown LA (and, via transfers at intermediate stops, to the Westside), and local trips on the Slauson corridor. It’s a flexibility that modernized regional rail has, and that other modes of transportation, which can’t mix local and intercity traffic as well, lack.

Leaving California, let us look at New York. There are perennial proposals for a new connection to LaGuardia (via an extension of the N) and an additional connection to JFK (usually using the Rockaway Cutoff). There is also a new proposal for a Newark connection via PATH. With the distinction between short-distance domestic and long-distance international airports (Newark is intermediate between the two), we can analyze these proposals. Newark is the easiest to dispose of: the cost is extreme, $1.5 billion for 4 km above ground. It also has several design flaws: unlike the LAX connector I outlined above, this proposal is nonstop from Newark Penn, skipping the former South Street railroad station; the lack of intercity service improvement and the poor service to the Midtown hotel clusters doom it as a CBD connector.

The JFK proposals are problematic as well. The AirTrain connection to Jamaica is quite useful, since it lets people from all over Long Island connect to the airport. Improving JFK access hinges on improving service to Jamaica, then: through-service from New Jersey, higher off-peak LIRR frequencies, reelectrification with catenary to permit Amtrak send Northeast Corridor trains that aren’t needed for Boston service to Jamaica. East Side Access improves JFK access as well, since it allows LIRR trains to serve Grand Central, which is closer to the Midtown hotel clusters than Penn Station. Ideally there wouldn’t be an AirTrain connection, but it’s the best that can be done given existing infrastructure and given Jamaica’s importance. A Rockaway Cutoff connection, which branches from the LIRR Main Line west of Jamaica, would not help Long Islanders go to JFK; it would also not be able to carry intercity trains, since Amtrak trains to Jamaica can serve both airport riders and Long Island riders, each of which groups alone is too small to justify intercity trains on its own.

In contrast, LaGuardia proposals are better, since for a close-in, domestic airport, service to the entire city is more important. I remain somewhat skeptical – airport connectors are still overrated – but less dismissive than of Newark and JFK proposals. LaGuardia travelers from the Upper East Side, which as far as I remember supplies a majority of its departing traffic, would have to transfer at 59th Street; but they have to detour through 59th or 125th via taxi already, and the subway would not get stuck in Manhattan traffic. Conversely, there is much less need to connect the airport with the suburbs and with neighboring metro areas than there is with JFK, which means that there is no point in constructing people movers to the LIRR.

Finally, let us look at Chicago. O’Hare has the airport connection of a domestic airport rather than that of an international airport. There are plans for an express link to the Loop, but these do nothing for departing passengers from neighboring areas. While airport connectors tend to be overrated, express premium-fare links are especially overrated, since they give business travelers dedicated trains, on which they always find seats, without needing to commingle with lower-income riders.

However, some of the Midwestern high-speed rail proposals include a connection to O’Hare from the outlying metro areas, and this is good planning, assuming the cost is not excessive. SNCF’s proposal includes a bypass of Chicago that serves O’Hare, similar to the Interconnexion Est. A second step, if such a connection is built, is to attempt to connect regional lines to it, if they are electrified. This includes both inward connections, i.e. a frequent commuter rail connection to the Loop or West Loop with good connections (ideally, through-service) to other commuter lines, and outward connections, i.e. low-speed short-distance intercity lines, such as to Rockford.

In all of these cases, the common thread is that the connection to the airport does not need to be a premium service, marketed only to the business traveler. These services are never the majority of airport transit ridership: see Hong Kong, Tokyo, and London numbers on PDF-p. 28 here. However, it does need to provide service to both departing and arriving passengers, and for a major international airport, this requires good service to the suburbs and to adjoining metro areas. The optimal technologies are often bundled together with premium fares – high-speed rail is in many countries, mainline rail is in North America – but the benefits come from features of the technology and service pattern, rather than of the branding. Good transit projects connecting to airports will make sure to have the correct service reach, while at the same time not excluding local riders.