So here’s Roppongi:
Obviously very few of us can achieve the urban intensity of a city like Tokyo, but still, here’s what is by all intents and purposes a vibrant and pedestrian-friendly retail district which exists directly underneath an elevated expressway. Since we US Americans have a lot of elevated freeways, since removal often isn’t practical and since trenching can be cost-prohibitive, it’s worth asking – What’s different?
The underside is solid, painted white, and lit.
This is huge. Standard North American freeway architecture has individual beams with dark, shadowy voids in between. These beams are typically unpainted, and left to weather with age to become a dark brown color. This suggests the underside of the freeway as a shadowy realm. Who knows what could be lurking under there?
For instance, at one point WashDOT found a homeless shanty that had been erected on the underside of Seattle’s 520 bridge. The kid had sunk metal spikes into a column, bridged the flanges of two beams with plywood, and tapped into the street lighting electrical system. There was a mini fridge and a playstation in there! This kinda thing doesn’t happen with the steel box that roughly half of the Shuto network is constructed with.
With a solid, well-lit underside, the freeway simply becomes the ceiling of the street “room,” a logical extension of the “street wall” concept into the vertical plane.
Pedestrian attractors are on both sides of the structure
Another big one. Many of the US’s elevated freeways skirt waterfronts or other areas where the freeway separates a fringe area from the whole of the city. In this context it’s very easy to cut off the fringe area. This is one of the big differences between SF’s (now dead) Embarcadero Freeway and Seattle’s (soon to die) Alaskan Way Viaduct. In SF the buildings on the waterfront were sparsely spaced and even today many are reserved for industrial and maritime uses. Whereas in Seattle the waterfront was long a tourist attraction, with a high density of attractions. Hence there’s always a decent amount of foot traffic on Alaskan Way (the surface street) even though it’s 50 feet from a double-deck expressway.
The underside of the structure is open, with good sight lines
This is pretty much the opposite of standard US practice. 1960’s planning literature repeatedly emphasizes parking as a preferred use for under-freeway space. But a bunch of parked cars reinforce the status of the under-freeway space as a shadowy warren. Think how many action movies rely on shootouts in parking garages – Jason Statham crouching behind an SUV, watching for the baddie’s legs to move – and you see the issue.
Now the question that naturally arises is,
What about the Pierce Elevated?
It’s not going anywhere. And it’s probably not getting trenched anytime soon. How can we make it more… walkable?
The City has already done a decent job of making it more attractive from the street side by planting closely-spaced street trees and erecting wrought iron fences. This creates a sort of street wall at the edge of the freeway and defines the edge of the street instead of letting it filter out into some vague, shadowy and undefined realm.
Most of the Pierce’s bents have four or five columns, so there’s really not a lot you can do to make it open and airy underneath. In the long term you could probably build out some retail space down there, but as a cheap solution the iron fence works.
What you’re left with then is the beams and the lighting situation. One of the substantial pedestrian flows under the Pierce Elevated is from the Inbound bus stop on Louisiana at Travis three blocks east to the Downtown Transit Center. Presently the point where you get off the bus has NO overhead lighting of any kind. This is really not the way it should be.
Houston’s concrete is naturally substantially lighter than most other cities, by virtue of climate and geology. So I’m not sure the white paint is even really necessary here. But installing decent lighting mounted to the underside of the structure, and leaving it on 24/7, would make a huge difference. Do it with LEDs and the electricity cost becomes almost negligible.