Capping Vine Redux

Remember this post? Remember this picture?

Well, with the new Mormon apartment building, I thought I'd bring it back to life, and put more meat on them bones.

Here we see, in purple, the major developments near Vine between Broad and Logan Square: the Mormon Temple, their Meetinghouse, the new apartment building at 1601 Vine, the Provence, and the apartment buildings buttressing Broad and Callowhill. Under it, we see the old cap plan. Intermingled with these, we also have some additions: several mews structures to take advantage of the increased desirability, and a small park over the exit ramp at 15th and Vine.

In the cloverleaf, we build a new "Sydenham Mall" (Sydenham being the name of the interstitial street between 15th and 16th); flanking it, large buildings fronting each of the four corners. They would share mechanicals and loading docks in the cloverleaf curve; inasmuch as possible, they would cover the interchange. Retail fronting Sydenham would lead up to the Provence*; retail fronting 16th would help urbanize that street further; flex space would front 15th.

Between all of these additions, the Vine Street Expressway would be completely hidden from 12th to 21st-ish. It would become the perfect example of the proper placement of heavy transportation infrastructure in the city--grade-separated, out of mind.**
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*If the Provence is built. As you may recall, I noted in A Provincial "Provence" that turning the cloverleaf green is, in fact, the worst possible for it.
**Remember, in Death and Life, Jane Jacobs noted that the most marginal uses--and hence the worst land values--were (in her time) usually located next to railroad tracks; this can be expanded to include Interstates today, for various reasons. Both are heavy infrastructure. The fact of the matter is that heavy transportation infrastructure, while indubitably necessary for the city to function properly (to get imports in and exports out à la her economies trilogy), also have a depressing effect on adjacent land. My extension of this point is--one of planning's major goals should thus be minimization of this effect by making heavy transpo infra "invisible" from an urban-dynamics point of view.

Tactical Urbanism: Shared Streets Edition

Now we have two tactical urbanism tools to encourage shared streets.

1. No Parking signs. Like in Malibu, of all places. Yes, I'm serious. Wash West has the highest shared-street quotient in the city, and many of these streets have strong--signposted--No Parking regulations in place, as well as bollards preventing parallel parking on sidewalks. (In saying this, I retract my previous post on the subject: I was clearly wrong). The easiest way to make this happen, if you live on a Small Street, would be to contact your block (group) captain and request that on-street parking be removed from your block and it be turned into a shared space (a tour through Wash West may be helpful here). If that doesn't work, more...tactical solutions may be needed.

2. Pedestrian sharrows. Create a large stencil and paint it at the head of a small street.

Like so.

Expressway Caps

Columbus has an interesting expressway cap on High Street. Check it out.

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High Street cap from the sky

While the Tribune blog bloviated over its similarities to Columbus' former (lost) Union Station--alas, poor Union Station--for planners that's not the key takeaway: instead, the key takeaway is that it is very much possible (though not cheap) to build light freeway caps. (This one cost just under $10 million.) The other takeaway is that a freeway cap need not be just for recreational land use. Boston, I'm looking at you.

High Street crossing the cap. Look, ma! No expressway!

Instead of a fully underground, Big Dig-type scenario, the Columbus example gives us some counter-ideas. When it is necessary--for whatever reason*--to run a sunken expressway through an urban area (usually due to the inertia of one already existing), it would be far better--and cheaper--to mitigate the impact by deploying these cap structures--or more accurately, in most cases, salable cap slabs.

Such as these slabs in this unfinished development.

In either case, the interventions are different than the major interventions that usually involve acquiring an Interstate's air rights: in those cases, space for full cores needs to be found, and anchored on solid ground. In this case, however, the structures are diminutive enough--single story commercial, townhouses, walkups, or possibly retail with a townhouse or walkups atop--that they need only basic infrastructural hookups (electricity, plumbing, and fiber)** that can be routed through the cap--no need for such expenses as elevators. Additionally, well-known green roof installation techniques can be used to add grass to whatever open space local zoning laws require in the rear of the property, please; a low wall (about 10 ft.) separates the livable space from the transportation space. With caps another possibility may be to provide a cap base along an entire city block that e.g. garden apartments can be built on. Unlike the cap concept, however, this concept would become a full tunnel and necessitate ventilation equipment somewhere on site.

Click it to see it in all its glory!

This is the first of the two concepts I whipped up for this post. The Vine Street Expressway is a sunken highway dividing--despite the crossing frequency--Center City from North Philly. The sunken section runs from 10th St. to 22nd St., or 12 blocks (with 13 spans). It additionally passes by Logan Square, a pretty dismal City Beautiful mess anchored by an excessively autocentric traffic circle. This model proposes closing open caps currently situated between 18th and 21st Sts, and providing for small commercial or multipurpose salable slab space alongside each of the other bridges. As time goes on, cap additions between these caps can completely conceal the expressway's existence at street level.

Oooh shiny. Clicky.

This is the second. Where the Vine Street Expressway is ideal for more fly-by-night and urbanist interventions, Society Hill is ideal for something more closely approximating garden apartments, as the image explains.
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* And usually it's not, from a technical perspective. Big Dig-type projects should usually be opposed on principle (pork-barrel automotive spending): what I am proposing here is a mitigation strategy when expressway closure has already wormed out of the picture, or for retrofitting of existing sunken expressways.
** Electricity for climate control and cooking as well as power; plumbing means fresh water and sewer hookups; fiber allows for phone, cable, and Internet.

What Makes Up Walkability Anyway?

Yesterday, commenting on Strong Towns, I commented on how jogging paths and crosswalks don't make up "walkability" and the Walk Score showed that, giving the school a walk score of a cool 3. I contrasted the locally-highly-amenitized Kensington High School for the Creative and Performing Arts, on the border between Fishtown and Norris Square, with a Walk Score of 83, to demonstrate what a walkable school would actually look like.

And then I Walk Scored a commercial strip from my childhood. Here's what it looks like. It's pure sprawl, and an effort to traverse in anything that doesn't have four wheels and a motor. Yet it gets a Walk Score of 72. Why?

It occurs to me there are two aspects to "walkability" (or transit mobility in general): you have to have locational amenities--that is, somewhere to walk to, and traversal amenities--that is, what kind of effort it takes to get there. Locational amenities are places, and places such as stores, restaurants, parks, schools, churches, friends' houses/apartments/condos, while traversal amenities are the condition and quality of the trip. For pedestrians, this means wide sidewalks, good (and frequent and signalized) crosswalks, fairly narrow streets, and lots of interest and variety in one's surroundings, including variety in the built environment and of traversal paths; issues that decrease traversal amenity include poor sidewalks (if not no sidewalks), overly wide roads, poor crosswalks (if any at all), poorly set stoplights, overly deep setbacks (especially for commercial), highway boundaries (such as Bethlehem Pike in the example above or DeKalb Pike by King of Prussia; many suburban strips are, unfortunately, arrayed around these highway boundaries), lack of interest along path (few buildings, buildings too deeply set back, lack of usage distinctions, oversized parking, etc.), and so on.

Now, needless to say, locational amenities need to be weighted over traversal amenities. Locational amenity trumps traversal amenity when the area of traversal, from door to door, is relatively short (500 ft., say) and not blocked by some sort of boundary feature (fence, wall, waterway, cliff, highway, thicket, etc.) Desire lines in the suburbs routinely get etched through narrow hedgerows and woods, for example, for precisely this reason. However, there is also a horizon or sunset, beyond which traversal effort in the main trumps any kind of locational amenities whatsoever. Let's peg pedestrian sunset at 2000 ft. As the traversal effort increases, the need for locational amenities likewise increase, as a way to counteract the effort being expended and keep the pedestrian sunset from shrinking (to 1500 ft. or even 1000 ft., say). This shrink space indicates an increased importance of traversal amenity, meaning it now trumps location as the primary determinant in whether one will walk; beyond the sunset, this is in turn trumped by distance. The presence (or absence) of traversal amenity can be determined empirically, critically scaled, and then weighted against the scales of location (and location density) and distance.

The problem with Walk Score is frankly that it only measures and weights locational amenities, and then weights them by locational density as an address function. It in no way measures traversal amenity, or even traversal, for that matter; Walk Score perceives Airport Square and Montgomery Mall as being on opposite sides of the road and hence highly locationally dense; it does not register that to actually walk from the exit of Airport Square's Toys "R" Us to Montgomery Mall's entrance one has to traverse two goliath parking lots 500 feet each with a serious boundary feature (Bethlehem Pike) without any sort of safe crossing halfway between. It, in other words, fails to register that the built environment, with no pedestrian traversal amenities whatsoever perpendicular to the lay of the buildings, has effectively created a pedestrian sunset precisely as deep as the setbacks. Without pedestrian amenities, distance trumps location as soon as location ceases to be an independently viable draw.

Because of this, Walk Score is only a useful means of measuring pedestrian amenity when pedestrian amenity is there to begin with. We can see the contrast when we compare Montgomeryville's walk score with that of the closest Main Street, that in Lansdale. The implication is clear: either (a) Walk Score has to do a better job of measuring walkability viz. traversal amenities, or (b) a new walkability score is needed.