Blog buddy Bob Voelker at DFW Reimagined has a new post up about a recent trip to Taiwan. I grab onto a detail he points out about streets with express lanes in the center and expand:
The "center express lanes" reminds me of a metaphor that I use when discussing how to make busy arterials more amenable to development that wants to interface directly with those streets rather than back away from and defend its building with a parking lot.
When you cut a section across a natural stream channel, the fastest current is in the center (and at the surface, but depth doesn't matter for this purpose). The slowest current, and consequently where the most biodiversity is, is at the edges of the stream channel, where land (stagnant) and water (movement) interface and in some cases overlap. I'm not a fisherman, but I'm pretty sure fisherman will tell you these are also the best spots to catch fish, where they're feeding on all of that life at the edges.
In stream corridors (that receive too much runoff, too quickly from too much impervious surfaces) where the side current is too fast, it erodes the banks and extinguishes all of the life at the edges. Not unlike streets that are about fast movement all the way across.
Where the current is slow or "eddies" at the edge, is like pedestrian life on the sidewalks. It doesn't move in clean, clear predictable channels. It is the ballet of street life. People stop, people turn around. They cross. They meet. They window shop. They enter/exit buildings. Etc. Etc.
The best streets in the world, those that maximize BOTH movement capacity and real estate value are able to juggle need for "link/movement" and need for "place" (in leveraging maximum private investment in property along the public investment. The fastest traffic is at the center, and increasingly slower traffic as you move closer to the edges (such as browsing and parking lanes, buses that make frequent stops, bike lanes,
When this is done successfully, "movement economy" businesses can actually be urban and furthermore, the quality of place is such (because of the amount of amenity) other uses including residential, want to cluster up as close as possible to this center of gravity. It is sociopetal rather than sociofugal like our current road design and resultant building form.
In reality, this is all the public sector needs to focus on rather than every little detail of every development. Getting the right "bones" in place, the primary movement corridors. You get those right, you create a network of interconnected centers of gravity, that will naturally find their appropriate place in the hierarchy of scales (largest are downtowns, smallest neighborhood/village centers), the market will fill in the residential backdrop that populates these places.
See the attached images for more information:
Red in this street section is for fastest movement. These could be two lanes, or three, or four. One of the keys, since this is for primary arterials, is that the transit should be at the edge of this section. It will be slower than the more internal lanes since it stops frequently, but is still primarily about movement. However, it is also dropping off pedestrians which need to be as close to the slow movement as possible.
Yellow here, is still about vehicular movement. This is where your bike lanes, browsing lanes, and parking will go. The arrangement of these can happen in a number of different ways. In this case, I'm showing a shared browsing/bike lane since if a car is browsing it will be moving slow enough to comfortably share with bikes. If bikes need less restrictive movement, they should get their own dedicated lane. As with many roads, these are best determined by context and locally determined need, NOT by standardized sections.
Green, obviously is pedestrian only realm. Parking is the interface, as a stopped car lets out its newly formed pedestrians.
Also, it should be noted that just about any corridor naturally adapts to this arrangement. Think about the narrowest of pedestrian only streets. I'm thinking of two I'm very familiar with, la passeggiatta in Rome or stroget in Copenhagen. The slowest movement happens at the edges and people walk in the center. The same red, yellow, green occurs just within the scope of speeds that pedestrians would move.
La Passeggiatta, shown above, is actually a more general term for "evening stroll" that italians make after dinner. However, in Rome, the route has been immortalized through tradition. That happens in cities aged several millennia. This section happens to be one sided, but you can still see the red(walking)/yellow (sitting/serving)/green (building interface) spectrum.
Every street should have this thought of green, yellow, red pervading through it, so that buildings and the people that occupy them aren't continually spreading apart from each other. Furthermore, it is absolutely vital from an economic development standpoint to get this right along the primary arterials, where the most potential exists for new development for a couple of reasons:
1) They are currently underdeveloped because of car-centric development and the cannibalization that inevitably occurs because of the sociofugal nature. To recap, sociofugal means to fling people away. Sociopetal means to draw people in. Sociopetal places don't die because people are constantly drawn to them, therefore we continue to care for and steward these places. Otherwise, Rome and its monuments, a city that was essentially buried under twenty feet of earth 150 years ago wouldn't exist as it does today. And,
2) Movement economy is essential in creating both commerce and vital, lively places. Business needs to be by lots of traffic. Traffic exists as vehicle, bicycle, foot, or web traffic. The most valuable websites have the most traffic. The most valuable real estate ALSO has the most traffic when the sites can actually be accessed. You can't access sites along a highway because it is impractical to have so many stopping points or pedestrians along such dangerously high speeds.
Frontage roads were an attempt to ameliorate this truism, but they have also failed. Property along frontage roads are tremendously overvalued and in nearly ever case, in decline. The reason for first the overvaluation is because of the traffic (or assumed traffic) of highways. The reason they are in decline is because the traffic is a) one-way b)still difficult to access - especially if you are headed in the opposite direction, and c) still along a freeway and the frontage roads often move at similar high speeds.
Therefore, the opportunity is along the major arterials. If we can redesign those correctly, they'll become seams for interconnected, fine-grained, complexity aka urbanity. And our shiny, new big developments won't be so internalized, which has its own economic penalties or perhaps better put, economic governor (like in a golf cart) for how valuable it can ever be.