A border—the perimeter of a single massive or stretched-out use of territory—forms the edge of an area of “ordinary” city. Often borders are thought of as passive objects, or matter-of-factly just as edges. However, a border exerts an active influence. “The curse of border vacuums” The Death and Life of Great American Cities (p257)

Maybe it’s just because I read Kevin Lynch through the lens of Death and Life, but I was surprised to find Jane Jacobs referencing Lynch’s concern about edges as an aesthetic matter. Jacobs’ focus is on the functional.

When I introduced The Image of the City, I offered this note on edges:

Edge - This is paramount in Jacobs’ discussion of border vacuums. These are the elements such as rivers, railroad tracks, or anything else that might be a barrier to paths. It may also be where two different use districts meet. They can be any linear element we don’t consider paths.

I hope some of this definitional material helps. Here’s why it’s important:

As I’ll explore tomorrow and later this week, the elements of the city that create these edges are not inherently bad. We need, for example, railroad tracks and limited access roadways; we also need large, single purpose districts, such as hospital and university campuses. However, the designers and placers of such elements do not consider the functional costs these elements require. Jacobs hopes not just to add these costs to the cost-benefit analyses behind such placement decisions, but also to understand the functional impact and provide strategies to minimize it.

Pruitt-Igoe, St. Louis, 1968

This week I’ll be looking at another of the elements of The Image of the City that Jane Jacobs spends significant time discussing in The Death and Life of Great American Cities: the edge. Five chapters before discussing the limits of visual order, she dedicates a whole chapter to “border vacuums” created by edges - a phenomenon she recognizes in the failings of the modernist and Corbusian housing projects (see example above) and Daniel Burnham’s City Beautiful (see example below).

The White City, Chicago, 1893

Jane Jacobs explains two types of tactic to help clarify visual order for the city:

1. Emphasis
2. Suggestion

The tactics detailed in yesterday’s post were those falling in the former category, such as terminating vistas with landmark or interrupting a straight stretch of roadway with a plaza.

Jacobs’ chapter on visual order spends less time on the tactics of suggestion. That is, those that help unify a district’s character. Jacobs focuses on the street, again, listing different design elements that can help us perceive a street as a unified whole, even where there is diversity and vitality among the uses and structures:

• street trees
• strong and simple patterns in sidewalk pavement
• awnings

(cc) RachelH_ on flickr

(cc) Andrew A. Shenouda

Imagine a street where residences mix with commercial uses, where there is a mix of building ages and consequently their styles, materials, and craftsmanship. Adding such elements can suggest a unified whole.

These same strategies can be applied to larger districts. However, if every street and every district applies the same elements, the unified whole suggestion becomes untenable. The open sky can be a unifying element, but it’s presence nearly everywhere lacks the tactical weight of other unifying elements.

Town Planning in Practice by Raymond Unwin, 1909

Terminate your vista. Jane Jacobs shares the same sage advice as Raymond Unwin did 40 years earlier. Sites created by intersections like those from Unwin’s illustration above are great spots for landmark structures - statuary, civic buildings, churches, or even an attractively landscaped moment. Streets do not need to appear to continue on endlessly if you terminate and interrupt them well.

Kevin Lynch, contemporaneous to Jacobs, provides the the research and language for describing such a moment where two of the five elements of The Image of the City occur:

• Path
• Landmark (or substitute a Node)

Andres Duany, Elizabeth Plater-Zyberk, and Jeff Speck return to such concepts in Suburban Nation, where they discuss TND and other takes on The New Urbanism, noting how modern traffic engineering has made such intersections illegal. This makes it impossible to replicate a plan, such as John Nolen’s Mariemont, Ohio:

Mariemont, Ohio

I hope to get a few pictures of Mariemont the next time I’m down in nearby Norwood. But, even here in plan, you can see the streets interrupted by an important node at the town center. Note the civic buildings with their large lots - especially the Town Hall south of this node. Nolen sure could terminate a vista.

(cc) David Gane on flickrYesterday, I introduced Kevin Lynch’s five elements that make up The Image of the City in our minds:

1. Paths
2. Edges
3. Nodes
4. Landmarks
5. Districts

Last week, I asked whether architects hate cities. In her chapter on visual order, she sets up streets as our primary setting for viewing the city, and that it is problematic that they announce both activity and endlessness - especially under the tyranny of the grid found as an historical artifact of many cities.

Lynch backs Jacobs, suggesting that paths are the primary element in most of our mental maps because they are the setting in which we view all the other elements:

• Edges cut off paths
• Paths lead to nodes; sometimes, the intersection of two paths creates a node
• We see landmarks from paths; we orient ourselves along paths by them
• We travel through districts on paths

Paths are the key. The “problem” of visual order isn’t the activity on the street, it’s the false perception of an endless expanse of this activity. The architects that might hate the city have identify the problem incorrectly. Jacobs has some suggestions about how to use the other elements to solve this design problem - a much easier fix than:

• removing activity from the street
• ordering it in separate districts, or
• spacing it out so much that it makes sense at the speeds of an automobile

I’ll share those tomorrow.