Here’s a Google Maps image of Southport, a section of Fairfield, Connecticut with its own Metro-North commuter rail station:

Here’s an image at the same scale of Bourg-la-Reine, an inner suburb of Paris on the RER B, at the junction between the line’s two southern branches:

At Bourg-la-Reine, the buildings just east of the station are high-rise. There are local community amenities, including walkable schools, supermarkets, and pharmacies, and people can comfortably live in this suburb without a car. This generates significant RER traffic at all hours of day: outbound trains are often standing-room only until they reach this station even in midday, outside rush hour.

At Southport, there are a few townhouses near the station. But the roads are wide and hostile to pedestrians, and the nearest supermarket closes at 6 pm, too late for commuters returning from the city. Car ownership approaches 100%, and nobody rides the trains except to get to office jobs at the traditional peak hour in Manhattan (or perhaps Stamford).

The difference between the two places is so stark that they can barely be compared. Southport has 317 inbound boardings per weekday. Of those, 263, or 83%, are in the morning rush hour; the Metro-North-wide average is 63%, and the average on the SNCF-operated parts of the RER and Transilien is about 46%. Bourg-la-Reine has 4.5 million annual riders, about 16,000 on an ordinary working day.

A huge part of the difference is about service provision – Bourg-la-Reine has a train every five minutes midday, Southport a train every hour. But it’s not just about service. The RER has stations farther out, with somewhat less intense service, such as a train every 15 minutes, with comparable ridership. And the LIRR and Metro-North have little off-peak ridership even at stations with more frequent service, such as Mineola and Hicksville. Transit-oriented development (TOD) is as important as good service in such cases.

I bring up Southport because the RPA just dropped a study about suburban TOD that grades every New York commuter rail station between 0 and 3, and gives Southport the highest mark, 3. The RPA study looks at zoning within 800 meters of each station and considers whether there’s a parcel of land that permits multifamily housing with a floor are ratio higher than 1.25. Southport has such lots, supporting some townhouses, so according to the RPA it gets full marks, even though, by RER standards, it is like every other American car-oriented suburb.

Based on this methodology, the RPA identifies a number of good suburbs, and even comes to policy conclusions. It proposes more TOD in the mold of existing exurban New York examples, such as Patchogue. The model for the program is the real reason the RPA study is so weak: rather than calling into attention the big differences between land use at suburban stations in New York versus in Paris (or any number of big European cities with suburban rapid transit), it overfocuses on small differences within auto-oriented suburbia.

Some of the ultimate conclusions are not terrible. For example, the RPA is proposing linking federal infrastructure development to permitting more multifamily housing. This would improve things. However, the problem with this is twofold. First, it is unrealistic – the federal government gave up decades ago on enforcing fair housing laws, and has no interest in attempting to make exclusionary suburbs behave. Were I to propose this, hordes of American commenters would yell at me for not understanding American politics. And second, it misunderstands the nature of the problem, and ends up proposing something that, while unrealistic, is still low-impact.

The best way to understand the problem with the study is what author Moses Gates told me on Twitter when I started attacking it. He said that the RPA was looking at zoning rather than actual development. Since there is zoning permitting multifamily development within the prescribed radius at Southport, it gets full marks. With my understanding of what good TOD looks like, I would be able to say that this is clearly so bad the methodology must be changed; on Twitter I suggested looking at zoning within 300 meters of the station rather than 800, since the highest-intensity development should be right next to the station. I also suggested looking at supportive nonresidential uses, especially supermarkets. A development that isn’t walkable to retail at reasonable hours is not TOD.

The RPA does not think in this language. It thinks in terms of internal differences within the US. Occasionally it deigns to learn from London, but London’s suburban development is auto-oriented by European standards (transit mode share in the London commuter belt is at best in the teens, often in the single digits). Learning from anywhere else in the world, especially places that don’t speak English, is too difficult. This means that the RPA could not reach the correct conclusion, namely, that there is no such thing as an American suburb with TOD. The only exception I can come up with in the United States involves Arlington, on the Washington Metro, and Arlington is no longer considered a suburb, but really a full-fledged city in a different state, like Jersey City.

The other thing the RPA missed is that it drew too large a radius. TOD at a train station should include townhouses 800 meters out – but it’s more important to include high-rise residential construction next to the train station and mid-rise apartment buildings 500 meters out. Giving American suburbs latitude to place TOD so far from the station means they will act like Southport and allow small amounts of multifamily housing out of the way, while surrounding the station itself with parking, a tennis court, and large single-family houses with private swimming pools. This is not hypothetical: suburbs in New Jersey have reacted to court rulings mandating affordable housing by permitting apartments at the edge of town, far from supporting retail and jobs, and keeping the town core single-family.

Because the RPA missed the vast differences in outcomes between the US and France, it missed some useful lessons:

States should centralize land use decisionmaking rather than give every small suburb full autonomy.

TOD doesn’t need to be fully mixed-use, but there should be some local retail right next to housing.

Housing should be high-density right next to the station. A floor area ratio of 1.25 is not enough.

Publicly-funded social housing should be next to train stations, in the city as well as in the suburbs, and this is especially important in expensive suburbs, which aren’t building enough affordable housing.

Without suburban TOD, any regional rail system is incomplete. I wish I could have covered it at my talk, but I didn’t have time. Good service needs to run to dense suburbs, or at least suburbs with dense development within walking distance of the station. It needs to extend the transit city deep into suburbia, rather than using peak-only commuter rail to extend the auto-oriented suburbs into the city.