A post on Let’s Go LA from last year, about different suburban development patterns in different regions of the US, praises Los Angeles’s suburbs for having an arterial grid that allows some density and permits frequent bus service. The Northeast, in contrast, has a hierarchical system, of town centers surrounded by fractured streets and cul-de-sacs, at much lower density. This is how Los Angeles’s urban area has the highest standard density in the US, and one of the highest weighted densities, nearly tying San Francisco for second place after New York. It sounds like a point in favor of Los Angeles, but missing from the post is an analysis of how Rust Belt suburban development patterns reinforce prewar transit. Briefly, Western US grids are ideal for arterial buses, Northeastern town centers are ideal for commuter rail, which used to serve every town.
For a Northeastern example, the post brings up Attleboro as a historic town center. Look at the image and notice the walkable grid and development near the train station, although one quadrant of the station radius is taken up by parking. Attleboro is in fact the town with the oldest development on the Northeast Corridor between Boston and the Providence conurbation, and the only one that, when taking the train between Boston and Providence, I’d be able to see development in from the train. Sharon and Mansfield, both developed decades later, do not have as strong town centers. But conversely, many town centers similar to Attleboro’s exist in the Northeast: Framingham, Norwalk, Tarrytown/Sleepy Hollow, Huntington, Morristown, Paoli.
Now, a careful look at the specific examples of Norwalk and Huntington will show that the most walkable development is not necessarily at the train station. In both suburbs, the old town center is where the original road goes – Northern Boulevard and its eastern extensions in Long Island, the Boston Post Road in Connecticut. Huntington has a second center around the LIRR station; Norwalk has a much smaller second center around the South Norwalk Metro-North station. For the most part, the railroads went close enough to the older roads that the town center is the same, as is the case especially in Attleboro, Tarrytown, and Paoli, and in those cases, commuter rail can at least in principle serve jobs at the suburban town center.
This boils down to the difference between optimal bus and rail networks. Buses love grids: they typically serve the scale of a single city and its inner suburbs, and there it’s feasible to provide everywhere-to-everywhere service, which grids are optimal for. For the suburbs, this breaks down. Buses on uncongested arterial roads are still surface transit; an average speed of 30 km/h is aspirational, and that is for suburbs, not dense urban neighborhoods. On a road where the bus can average 30, cars can average 50, and cars can also use expressways without splitting frequency between different suburban destinations, speeding their journeys up greatly. Meanwhile, commuter rail can, depending on stop spacing, average 50-60 km/h easily, and an aggressive timetable can cross 80 if the stop spacing is relatively express.
There is no such thing as a rapid transit grid. Subway networks almost invariably look like a central mesh, often containing a circumferential line, with spokes radiating out of it in all directions. Mexico City has a larger mesh, approximating a subway grid, but its outer ends again look hub-and-spoke. Counting commuter rail, the hub-and-spoke system is as far as I can tell universal, with the exception of highly polycentric metro areas like the Ruhr. The spokes are rarely clean: they often cross each other (see for example the London Underground to scale). But looking at a city’s rail transit map, you’ll almost always be able to tell where the CBD is, where the inner-urban neighborhoods are, and where the outer-urban and suburban areas are.
At this distance, then, having a bus-friendly grid doesn’t matter much. What matters is having a good network of historical rights-of-way that can be used for regional rail, and a preexisting pattern of development following these lines and their junctions. In the US, the older cities have this, whereas the newer ones do not. In a suburb like Attleboro, good transit means good regional rail, with high all-day frequency, and a network of feeder buses timed to meet the trains. Grids aren’t especially useful for that.
And this is why, despite being so dense, Los Angeles has so little transit usage. Its street network is set up for bare-bones public transit, usable by people who can commute two hours in each direction and will never get cars. Because it was a medium-size city when its car ownership exploded, it doesn’t have as many town centers; its density is uniform. It has a higher weighted density than the Rust Belt outside New York, but its weighted-to-standard density ratio is much lower than those of Philadelphia, Boston, and Chicago. (It barely trails Washington, which has fewer town-center suburbs than the Rust Belt, but made an effort to actually build them around Metro; its Tarrytowns have Metro service rather than infrequent commuter rail.)
The optimal urban geography for urban transit is not the same as that for suburban transit, and the optimal street network for surface transit is not the same as that for rapid transit. Los Angeles could potentially excel at surface urban transit, but there’s only so much surface transit can provide the backbone of public transportation in a city. It has a handful of strong lines for rapid transit, and that’s a serious problem, which a grid won’t really solve.