Monday, June 6, 2011

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!
* Which says a lot about human nature, really.


  1. Great observations about complete streets vs. narrow streets, especially that point that the less safe drivers feel, the more safe everyone actually is.

    I will say that Philadelphia and the North End represent two very different urban traditions -- the North End is among the last of the "organic" street networks, while Philadelphia was one of the first of the orthogonal-grid-with-wide-streets plans that later became commonplace in American cities (by 19th century). The grid obviously has historical antecedents but William Penn's wide streets mostly did not -- gridded Pompeii's widest street was 32 feet, and most were 12-15 feet, in spite of the fact that cart traffic in late 17th century Philadelphia was probably not much greater than in a prosperous Roman city. The complete streets idea I think indirectly shows that we're still trying to figure out what to do with all that surplus width.

  2. Somewhat off-topic, both designs you show for complete streets are actually very auto-friendly and pedestrian-hostile.

    The first has 13- and 14-foot traffic lanes, versus 10 for the Manhattan avenues. The wide median and the tree-lined (more commonly dirt with a few trees) separation from the sidewalk reinforce high traffic speeds. Worse, there's a sidewalk on just one side of the road, and it's likely that the signal timing on such divided highways makes it very difficult to cross safely. For a better example of such a street, see here: note the street is much narrower, so despite the apparent lack of street wall, it's more pedestrian-friendly.

    The second has an unprotected bike lane. The problem with striped bike lanes is that they look like parking lanes unless there's a very large volume of cyclists; since there's no actual parking in that lane, all it does is encourage cars to think they have a very wide traffic lane and speed accordingly. It's still better than the first road, but the bike lane has to be protected.

  3. Charlie: Conceded, but the lived experience of Philadelphia (Walnut Street) suggests that 50 feet isn't necessarily unbearably wide, so long as there is ample pedestrian space and limited auto space.

    Alon: The first example was pulled from Strong Towns (link in post) and your criticism was their criticism. It is an example of what I was talking about, when complete streets are designed by people with a traffic-first mentality.

    The second example, the Spruce-Pine lanes, had a bevy of separate issues to deal with. Among these, the street was first re-striped just prior to repaving, and someone along the line mandated temporary parking in the lane for a couple of churches along the way. Regardless, the lived experience of these lanes has been exceedingly positive, and there are enough bikers using these streets that their bike-lane status is clearly signaled.

    Spruce and Pine were deemed successful, and a multitude of new lanes based on the same design have gone up in the year since, to the point Council has started trying to politicize the process.

  4. I should backtrack and explain that striped bike lanes aren't very bad. West 106th Street in Manhattan has them, and although I rarely if ever see cyclists there, the street is friendly to pedestrians. But this pedestrian-friendliness comes from the fact that the street is meshed together with the rest of the Manhattan grid. My several years old recollection of Center City's streets is that they're all pedestrian-friendly, with easy pedestrian crossings, low traffic speeds, and so on.

    My dig about unused striped bike lanes applies mostly to roads that could be pedestrian-hostile - for example, Baxter Street in Athens, GA. That street has striped bike lanes that function as a few extra feet of road lane more than anything.

  5. Agreed on that.

    And yes, urban Philadelphia (not just Center City) is extremely pedestrian-friendly. Wide streets are unusual rarities.