The alleyway is 10 feet wide, and the streets 30. This 30 feet is here translated into two 8' auto lanes (either both for travel or one for travel and one for parking) and two 7' sidewalks. You can go up to 50' in this design and use three 10' auto lanes (travel and parking) and two 10' sidewalks, or you could go narrower still and utilize naked streets.
This site design is easily adaptable, too. By switching out what we think of as proper "streets" with Radburn-style greenways, with the frontage side facing a 9' footpath with 7' access sidewalks, the rest of the former street space is converted into some small front (or side) yards. Thus, depending on frontage type and street width, this type of neighborhood can be optimized for (a) New Urbanism in a lower-density transect, (b) Landscape Urbanism (the Garden City), (c) streetcar suburbia, or even (d) autocentric suburbia. And since it's a '20s-type product, the results are already a pleasant known.
|Notice how small the amount of auto facilities is needed for adequate service--just 250 square feet of alleyway and 400 square feet of carport.|
Finally, some population statistics. Each block (500x210') has 20 single-family detached houses. With the average family size of 4.3 (2 adults and 2.3 kids), this means the average block population is 46; since each block is (roughly) two acres, this gives a per-acre population of 32, which thence gives a per-mile population of 20,480 with 4,050 square feet a house*...in much of the U.S., an urban population with a large house size, and a population density more than enough to support transit.
How was this done? By narrowing streets and removing ornamental lawns. In a Radburn-like situation, where streets are only needed for vehicular access, even the ornamental lawns are restored while the mean density remains extremely urban.
So bad zoning and bad subdivision regulation is the problem. To put it bluntly: setbacks destroy backyards just as overly wide streets and overly restrictive single-use zoning** destroys place.
* 45 x 45 = 2,025 x 2 = 4,050. This includes neither basement nor attic. Foursquare assumes four 20 x 20 rooms per floor, linked together by 5-foot-wide hallways and closet areas. Eight 20 x 20 rooms is quite spacious for most families.
Secondly, consider if this setup were twins instead. Per-family living area decreases to 2,025 sf plus half a cellar and half an attic (gross 2,025 sf), but the per-block, per-acre, and hence per-mile population densities would all double, now to 40,960 per square mile. Storage shed space would need to double, thus reducing one twin's backyard space, but this would be by a mere 100 sf.
** Notice not Euclidean zoning. A lot of people confuse the two, but when done correctly, Euclidean zoning is extremely flexible and can even include some form-based elements. It can, in other words, be inclusive. By contrast, ORSUZ is inherently exclusive, and when combined with a subdivision code which mandates hierarchical street patterns and excessive street width, functions like place-destroying dynamite. It is a pity traffic engineers know so little about cities since they have unwittingly designed or redesigned so many of them over the past half-century.