Stroad to Boulevard
is a blog dedicated to a single policy recommendation: the replacement
of American-style arterial avenues (aka stroads aka wide boulevards)
with
multi-way boulevards, with examples mainly drawn from the
French style. This is justified primarily by economic gardening: stroads
fail, according to
Strong Towns' Charles Marohn, to create
places of value
(i.e. offering a public environment nurturing of true value-creating
enterprise over life cycles). In addition, the benefits of urban
greenery are obvious, and (as Stroad to Boulevard's author points out)
benefit congestion by decoupling through traffic from causes of
friction, after
Jarrett Walker.
Multi-way
boulevards appear endemic to places of value in Europe, and rudimentary
versions even occur in places of high value in the United States--see,
for example,
Commonwealth Avenue,
Park Avenue, and
K Street--but
they have yet to be accepted here. Part of this is due to different
focuses in transportation planning, engineering, and design: in Europe, a
more multi-modal approach became more accepted and, yes, welcomed after
the Dutch bike revolution, whereas in the United States the
moving-cars-around orthodoxy continued to prevail. In essence, this
means American transportation engineering is now a generation behind
Europe's.
What I want to explore now are two things:
firstly, the variety of configurations available for such boulevards,
and secondly, ways to implement transit in the scheme.
What is the Minimum Width?
Stroad to Boulevard
carries, essentially, a single cross-section, seen above, for a typical
boulevard--100 feet. Of this, two access ways (curbside woonerven)
flank a four-lane central artery. Each access way is 28 feet, and the
central artery 44 feet, which implies that each driving lane is 11 feet.
It is possible to tweak some of the design features--for instance,
dropping a foot off each of the central passing lanes (not meant for
trucks anyway) and adding it to the access lanes. As woonerven, the
access area fulfills primary pedestrian and cyclist needs and secondary
auto ones (primarily loading and parking)--to function, in other words,
as a street--while the central artery is able to function as a road.
We'll call this
full profile--bidirectional, with twin woonerven. It is intuitive that this would be optimal for 100-foot arteries, such as
Broad and
Market streets.
 |
| Ignore the school bus. There would be no bus lanes at this standard. |
The
narrowest a full-profile multi-way boulevard could be would have two
driving lanes in the center, flanked by woonerven on either side; this
is created by removing the 100-footer's inner passing lanes. Taking 28
foot as the standard woonerf width, this implies that the narrowest
full-profile multi-way boulevard must be 76 feet--that is,
(28*2)+(10*2). Since few (if any) American streets are
exactly 76
feet wide, this implies that 80 feet is the smallest practicable limit,
which we would fill out by adding a foot to both driving lanes and each
access lane--(29*2)+(11*2).
If you split this in two, you would get a
half-profile
boulevard. The narrowest this could be would be 38 feet (or a more
comfortable 40 feet)--assuming no pedestrian realm at all to one side.
Add a sidewalk and you've got 50 feet.
The problem with this, however, is that
most nearly every 50-ft street is a
street, and thus not compatible with the MWB treatment. Even Paris'
Boulevard Haussmann is a
street. In fact, I do not believe there are
any
half-profile boulevards in existence--they gobble too much space with
their access woonerven, provide inadequate parking relative to their
full-street counterparts, and most 50-ft streets offer ample natural
pedestrian realms--almost a 1:1 sidewalk/street ratio as long as the
carriageway is held to reasonable widths (that is a ten-foot driving
lane plus two eight-foot parking lanes, for 26 feet total).
So
we can say the narrowest useful multi-way boulevard is 80 feet. This
actually works well for most American cities, which tend to have wider
streets that can better support this treatment.
Adding Transit to the Scheme
Most European multi-way boulevards have buses running in the outer through lanes, and some have
light rail in the median--see
this example
from Rotterdam. Such boulevards can have truly tremendous
widths--Rotterdam's Schiekade looks to be, for example, some 160 feet
wide--but we are focused on developing light rail along boulevards of
more manageable width.
Girard Avenue
is a good example: The 15 trolley runs in the median of what is here a
120-foot street. This represents an easy insertion into the 100-foot
multi-way boulevard standard--see above. Likewise, a transit median on a
100-foot multiway boulevard, like would be a relatively simple
insertion into the 80-foot standard--see below.
Washington Ave. would be a good possibility for this treatment--see below.
The problem comes when you need to put a transit median into an 80-foot way, like
Baltimore Avenue.
Without the trolley median, it would be equivalent to 60 feet, too
narrow for a full boulevard. Could a sacrifice need be made? Just the
woonerven--
Stroad to Boulevard shows us
the way.
While that post is about 66-foot streets, a crop of three feet on both
sides brings us down to 60 feet, enough to insert the 20-foot transit
median in between. This is, again, perfectly encapsulated in Rotterdam,
on the
Middellandstraat:
Even
where the street is too narrow to support full access woonerven, it's
still possible to support a transit median. But what about 60-foot
streets, like
Germantown Avenue? This final class
does
require a sacrifice--Do you give mass transit a dedicated right-of-way
and cut parking? Or do you mix traffic in two travel lanes and provide
it? Both solutions require a tradeoff: with the former you have better throughput on all modes, but most constituencies
demand parking and reject any proposal reducing it, Shoup be damned.
So in conclusion, we can say that, firstly, the nature of a multi-way boulevard makes 76 ft. its absolute minimum, as that width has
two
driving lanes coupled with mirrored woonerven; this can be retranslated
into an 80-foot standard for most American municipalities; secondly,
that the addition of transit lanes blows the width out a bit, and that a
100-foot transit boulevard is analogous to an 80-foot multi-way
boulevard, 120 to 100, and so forth; thirdly, that transit provision on
sub-100-foot streets requires a
transit avenue, built like a Dutch complete street; and fourthly, that at 60 feet a tradeoff must be made between throughput and parking.
While this post is by no means perfect, consider it a framework
for applying transportation engineering and urban design to the
streetscape; consider it a framework for implementing European design
standards in American situations.
