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.

Sharing Space

In the past I've (blasély) talked about naked streets, or as they are more euphemistically known, shared space, mostly in the context of other work, such as understanding street hierarchies. Now I would like to offer a few suggestions on realizing shared space:

1. The essence of shared space is that the travel ways (carriageways or cartways) are shared between all modes. Very narrow streets in older cities are often naturally shared spaces.
2. The lone useful metric of success in measuring fully shared space is whether or not walking in the middle of the road feels comfortable and natural; this is because of pedestrians' tendency to favor sidewalks wherever feasible; when pedestrians can effectively lay a territorial claim to the middle of the road, the motorist's response must be to accommodate to the pedestrians' territory, rather than pedestrians being excluded from motorists' territory. The pragmatic application of this is that shared space forces a natural speed limit, for motorized transport, in the range of 15 mph or 20 kph. In other words, sharing space naturally caps design speed.

This is the theory. Not rocket science, is it? Now to some application guidelines.

3. There is a clear hierarchy of streets even within the shared space paradigm; this hierarchy manifests as the distinction between residential and commercial shared spaces. This is in part because commercial shared space can be a bit more forgiving than residential.

Let us now elaborate the design guidelines for what both types have in common.

4. The street is narrow to very narrow. In most North American settings, this narrowness can be accentuated with onstreet parking.
5. The street is unidirectional (one-way).
6. Buildings alongside shared spaces are close together and cluster on, or close to, the lot line.

Now, let's get on to what describes a residential shared space.

7. There is little, if any, differentiation between carriageway and non-carriageway on shared-space streets. A small "sidewalk" may still be allowable as a space for street furniture (such as stoops, benches, trash cans, or street trees), but this space should not extend further than 3 feet from the lot line: pedestrians will still favor sidewalks when the sidewalk is as narrow as 5 feet.
8. The street is rarely more than  35 feet wide, and is, indeed, frequently less.
9. There is almost always only one travel lane; this travel lane is usually 10 feet wide when it accommodates automobile traffic.
10. The street must be quiet, that is, with an AADT under 500.
11. Parking lane(s) can be provided on either side of the travel lane: shared spaces can thus vary in width from sub-10-foot (very rare) to about 35 feet (fairly rare). Because the cars are parked close to the lot line, there is little comfort space for pedestrians there, bringing them out into the middle of the road. Onstreet parking is often an excellent way to artificially narrow a road.
12. Residential shared spaces tend to break into three typologies: the 10-foot class, with only one lane and no onstreet parking; the 20-foot class, with one travel lane and one parking lane, and finally the 30-foot class, with one travel lane and a parking lane on either side.

Commercial shared spaces are a bit different.

13. Commercial shared space is different from residential primarily due to the presence of storefronts facing the street.
14. Where there is shared space with a parking lane and commercial facing one side of the street, the parking lane always goes on the other side.
15. Commercial shared  space can have deeper sidewalks: up to 10 feet, due to the importance of window-shopping in commerce. This is especially true where there is parking on both sides of the all-mode travel lane.
16. It may be the case that commercial shared space can handle multiple travel lanes (no more than two). However, if this is so, the travel lanes still must be unidirectional if side-by-side, and bidirectional if and only if the parking lane is provided between travel lanes, and that if there are two travel lanes, then there must be direct access from the sidewalk to the travel area on at least one side (i.e. no parking lane).
17. This necessarily means that commercial shared space can be no more than 50 feet wide in most cases, with the possibility of 60 foot in the extreme case of having two parking lanes sandwiched between the travel lanes.
18. Through-traffic not wishing to use the commercial street needs to have a bypass easily available. This is particularly important since space sharing in popular commercial areas is likely to massively depress AADT along that particular road.

From this discussion, I would like to suggest that good 30-foot typologies would be (a) storefront-sidewalk-travel-sidewalk-storefront or (b) storefront-sidewalk-all mode travel-onstreet parking-lot line (non-storefront); 40-foot, (a) storefront-sidewalk-travel-travel-sidewalk-storefront or (b) storefront-sidewalk-travel-parking-sidewalk-storefront; and 50-foot, (a) storefront-sidewalk-travel-travel-parking-sidewalk-storefront, (b) storefront-sidewalk-travel-parking-travel-sidewalk-storefront, or (c) storefront-sidewalk-parking-travel-parking-sidewalk-storefront. Commercial streets narrower than 30 ft. can also, of course, occur; indeed, at the narrowest widths, they would be busier versions of residential shared space. Madrid's Calle de Preciados is one such example.

Delineating shared space is my next topic. Of course, the best way would be by use of a concept I call materials assonance, where particular materials are used to define how such-and-such part of so-and-so street is supposed to behave. Belgian blocks, for example, could define parking areas, while brickwork defines through passages, and slate, areas where street furniture goes. But implementation of a materials assonance plan would take quite some time, and would likely be undercut by state DOTs' insistence on confusing streets with roads. In the interim, before materials-assonance plans can be tried out, I would suggest a simple paint sheme:

Sharrows are already being used to identify spaces shared by bikes and cars. If the sharrows itself is what is used to identify shared space, then why not take the concept one step further and use it to define where pedestrians have right-of-way as much as cars? Furthermore, bike shared space is included in pedestrian shared space, so this sharrows is even more general than the bike sharrows. Painting pedestrian sharrows at the entrances to shared-space networks would territorialize the interior of the network for the pedestrian, and over time, lay the ground work for areas to develop materials assonance schemes in.

Thoughts on Old Urbanism

The first thought I have on Old Urbanism is about street width. Old Urbanists--particularly Nathan Lewis and Charlie Gardner--argue that our streets should be narrower. A lot narrower.

I have no quarrel with this, in principle. There really can't be much of an argument that postwar streets are excessively wide. When I learned in Land Use Planning 101 that the 1960 Philadelphia Subdivision Code mandated streets of at least fifty feet wide, I was shocked; in the lived environment of urban Philadelphia, 50 feet (three traffic lanes and two sidewalks) is the widest a street feels comfortable at.With the exception of the grand boulevards or proto-grand-boulevards (for example, Broad, Market, JFK, Washington, Spring Garden, Girard, Delaware, the Ben Franklin Parkway), no street in Philadelphia's urban core is ever historically* more than 50 feet wide, and the traditional driving of alleyways through the middle of blocks results in a network of ever-narrower streets and mews. Even so, since Philadelphia's primary grid is built up of 50-foot-wide streets (arterial streets, to the Old Urbanists), the mix here is closer to 49-49-2, in terms of narrow streets, arterial streets, and grand boulevards. This hasn't impinged Philadelphia's urbanism a bit.

Secondly, traffic density can also be a determinant of walkability or human-centrism. The primary Chestnut and Walnut Street shopping core is aligned along a pair of 50-foot-wide streets with two ten-foot sidewalks, two traffic lanes, and a parking lane**, but pedestrians and automobiles are segregated due to no more than the sheer force of traffic. Midcentury planners attempted to pedestrianize such streets--Chestnut was pedestrianized for a while--to disastrous results.

That said, I think that no more than the barest handful of streets need be more than 50 (or at the very outside, a very dense 60, like Ridge Avenue here) feet in width. Beyond this, they split rather than knit. Different neighborhoods also require different street widths to feel comfortable. Neighborhoods built on the picturesque-suburban model*** (such as Wynnefield) feel most comfortable with 50-foot roads; more urban neighborhoods are more comfortable with roads that run between 15-20 ft. and 50 ft., with each city having its own idiosyncratic alchemy of the two: this subtle alchemy helps creates a sense of macro-place: we are here and nowhere else.

The second thought I have--since streets are so wide and setbacks so deep--is that we can narrow our streets, and cities with excessively wide streets can make a pile of money by literally selling off excessive street width, in addition to other densification strategies--granny flats along the alley, carving excessively-deep front yards into new buildable parcels, and flat-out per-parcel redevelopment. In places like Detroit, where, for example, the widest streets can reach 200 ft., you can get whole new blocks.****

There are other ways to ameliorate excessively wide streets. Transforming their centers into various types of green space (hedges, swales, and even alamedas) is a good way to make them less excessively autocentric; an alameda is--additionally--a good way to provide bike facilities in underutilized street space. In a handful of instances, going farther is also an option: a trolleyway down the center of this greened space in the center of the street, maybe?
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* Some streets have been widened since. Some the numbered streets accessing the postwar office core of Market West have been widened to 60 or as much as 80(!) feet.
** I do dispute on-street parking a bit...although not by much. The occasional on-street parked car helps control speeding and defines the carriageway, for autos, and effectively becomes a piece of street furniture presenting a lived feeling in the neighborhood for pedestrians: good examples are this narrow (30 ft., I think) street in Manayunk and this street in Wynnefield.
*** Picturesque suburbia is heavenly. Post-picturesque-suburbia becomes ever more hellish.
**** This is not to say that Detroit has a market that can take this additional density, however.

Complete Streets and Naked Streets

A naked street in Britain

 Two major new approaches to street designing are being tested in Europe and the Americas: complete streets and naked streets. These approaches emphasize completely different aspects of the street: by separating every conceivable use into its own carriageway, complete streets emphasize the transportation use of the road, while by designing the whole road at a pedestrian scale, naked streets emphasize its public-room aspect. Local street space, whether a grid byway or suburban cul-de-sac, is an ad hoc shared space, if not de facto, which is why I prefer the earlier term "naked street"--a street space designed to be shared by motorists and pedestrians.

A complete "road" in Minnesota. Courtesy Strong Towns.

Because of complete streets' transportation aspects, they can range in width all the way from fifty feet (Philadelphia's historic street width) on up; it is difficult to downscale them any further. Complete streets usually have, at the very least, two ten-foot sidewalks and a bike lane in addition to traffic lanes; worse, the traffic engineers have a predilection to design the traffic lanes first, creating "complete" roads--still designed for cars first and foremost, with non-motorist design features added at the end of the process to placate NIMBYs and such. Essentially, the added carriageways (two sidewalks and bikeway) become expensive and nigh-useless ornamentation.

Spruce-Pine complete street design. Note that the total width must be 50 ft., and everything else flows from that.

However, complete streets on a small scale, such as Center City's Spruce-Pine bike lanes, with two 10 ft. sidewalks, a 10 ft. traffic lane, 10 ft. parking lane, and 10 ft. separated bike lane, can make sense in the broader urban context, as a way of deploying velocentric arterials into the street grid. Larger complete streets at boulevard scale, such as the Wynnefield Heights plan's proposal to widen City Line Avenue, in order to incorporate a dedicated 30 ft. transit right-of-way, four 12 ft. traffic lanes (six southeast of Monument), and two 11 ft. sidewalks, for a grand total width of 100 ft, similarly, only work in an arterial context with abundant crossing possibilities and superlative transit access. The fact that complete streets only work on arterials makes it temptingly easy, especially when the arterial is a highway arterial, to overengineer it into a complete "road" instead. For engineers, who seem to be trained to put as much concrete into something as the budget will bear rather than optimizing the mix of uses, this temptation is overbearingly powerful.

Naked streets are primarily European, and emphasize narrow streets lined with pedestrian uses and amenities, no signage whatsoever, no barrier between pedestrian and motorist whatsoever, and very subtle (texture changes are popular) differentiation between vehicular and non-vehicular "zones" on the street. Since scale and detailing prioritizes the pedestrian, a naked street is in essence a pedestrian zone the motorist "borrows" for the duration of his trip. Since this is not the motorist's element, the perception of a lack of safety, on his part, is greater, and thus (ironically enough) the street is safer*. They are clearly rooted in traditional urban paradigms, and are thus of great interest to Old Urbanism, as a nascent movement of sorts. Unlike complete streets, narrow streets can fit in far narrower rights-of-way--even as narrow as the 12 ft. Nathan Lewis likes, or, in the American landscape, probably more commonly the standard width of the city's streets, as determined by prewar building tradition (50 feet in Philadelphia, for example).

Since complete streets' and naked streets' optimal widths are so different, with only the teensiest overlap at 50 ft., a scalar system immediately suggests itself...a scalar system which looks, remarkably enough, quite like Philadelphia's grid, with 75 ft. complete-street arterials, 20 ft. naked-streets, and finally sub-20 ft. mews running through the blocks defined by the naked streets (Philadelphia's grid is historically 50 ft., with the exceptions of Market and Broad, at 100 ft., all of which was considered generously wide in 1700). The end result is a street paradigm which promotes a built form extremely close to the older parts of Philadelphia and Boston, such as can be seen below.

North End, Boston, top, and Washington Square West, Philadelphia, bottom. Both are taken at 500 ft. scale on Google Maps. Both neighborhoods are excellent surviving examples of traditional urbanism in American cities--indeed, this is what makes the North End such a tourist attraction!

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* Which says a lot about human nature, really.