Further out, where the streetcar lines helped settle early suburbs, there are corridors of activity which also correspond to low car ownership rates and population density. Public transportation acts as a "walk accelerator" making it possible to travel on foot over longer distances and faster than a person could sustain alone. The streetcars are mostly gone, replaced by buses and light rail vehicles, but many of the land use patterns remain -- despite decades of automobile-oriented public policy.
The MBTA has a "key bus route" program which has selected 15 bus routes for certain service guarantees about span and frequency. That's great, although a bit mysterious (why those 15?). The agency has slowly pushed for improvements in those particular routes, with the construction of the improvement program coming this year (finally). While a key route program might make sense from a transit agency's point of view, it doesn't necessarily correspond to the needs of urban neighborhoods, which are broader in scope. The city needs to consider land use and transportation together when make future plans. Historically those two subjects have been the purview of separate agencies, in Boston, and as a result, both have suffered.
Today, it's becoming fairly widely understood that the presence of a subway station ought to make a big difference in how development is conducted in the vicinity. However, that's too limited a view. I believe that concept should be extended further. Non-car surface transportation, whether it be walking, biking, trolley or bus, is far too important to be neglected in the overall land use and transportation planning picture. In addition, there are plenty of neighborhoods with current residents that deserve better streets and access to the city around them.
With that in mind, I drew up a rough sketch of a "key corridor" map which is loosely based on the idea of "key bus routes" but intends to have a larger scope that encompasses land use planning, pedestrian safety improvements, and bike routes as well. The light blue lines, dots and polygons are the places where walking, biking and transit ought to be emphasized. The black lines are connections that are outside the city's developmental scope, and there's also some regions highlighted in turquoise where future changes are anticipated. The map is far from complete, so I welcome comments. The core of Boston is largely omitted, since it should all be considered a "key" region.
You'll notice that many of the key corridors follow existing bus routes (key or not). That's because there is already a strong convergence between walkable areas and bus service. But the starting point is different. Rather than saying: "here's a good, frequent bus route" I am saying "this is a corridor near densely populated areas where people walk, and it ought to have high quality, frequent transit service of some sort." For example, the corridor between Roslindale Square and Forest Hills does not have a "key bus route" but it is, nonetheless, a very heavy ridership area and those parts of Roslindale are a fairly walkable area. Western Ave in Allston is another case, where the 70 and 86 buses are well-used but neither of them is a key route. That street is going to see some major development, as is the rest of Allston, and the bus stops along it ought to be designated for improved service. In addition to Allston, other neighborhoods on the map have historically been treated poorly by transportation planners, and have an existing population that can benefit from a commitment to expand the walking city.
Mayor-elect Walsh has claimed that he wants to conduct walk audits out in the neighborhoods, explore dedicated bus lanes, and better bicycling infrastructure. These key corridors could be the starting point for those kinds of improvements, as well as a land use planning process which is oriented around supporting walkable neighborhoods with convenient, frequent transit connections. A subway station is a fairly large commitment from the transit agency to providing "good service" in a particular area. A bus stop is not much by itself. But a planning process could make real guarantees about service, and give the same kind of commitment, and the same kind of environment in which to grow neighborhoods. We're not likely going to see too many new subway stations in the next few decades, especially with Boston's geology. So it's especially important that we are able to nurture walkable neighborhoods that are based around improved surface transit, and that new development gets directed into places where it can fit good transit geometry, rather than contributing to the traffic congestion and sprawl problem.