Good Cul-De-Sacs and Bad Ones

The Sustainable Northampton Plan disfavors cul-de-sacs. Page 51 states:

Avoid creating cul-de-sacs and dead ends when possible and instead create a network of streets. Dead end streets, while desirable to some residents, add significantly to the delivery of city services and increases traffic flows to other local streets…

Kohl Construction’s latest condo proposal for North Street contains two cul-de-sacs:

In the past, we have objected to the Sustainable Northampton Plan’s aversion to cul-de-sacs as overbroad. Some cul-de-sacs are handsome, safe, thriving micro-neighborhoods that are well integrated with their larger surroundings. Northern Avenue strikes us as a good example of a healthy cul-de-sac:

What makes some cul-de-sacs good and others bad?

Professor Bill Hillier and Simon Shu offer clues in their 2003 paper, “Do Burglars Understand Defensible Space?”

We see a clear tendency for burglaries to be less frequent on the most integrated lines, and more frequent on the segregated lines. This was confirmed by statistical analysis, and shown to be statistically ‘significant’. Similar results were found in two housing estate areas…

[In Figure 2] we see a marked tendency for burglary to occur in the deeper parts of cul-de-sacs, rather than in the ‘shallow’ parts that are directly visible from the nearby through street. If we then look at the pattern in the top left quarter of the map, we see again that burglary is found not on the first line of sight into the cul-de-sac system, but in the deeper parts, and also on the footpaths which link the cul-de-sacs. Looking to the right side of the map, we see that the burglaries that occur on dwellings with through street addresses are mostly accessed through back alleys, or long driveways which conceal the house from the street.

…The main curving residential streets [in Figure 4], which have greater linearity and integration, and are lined on both sides with dwellings whose entrances can see each other (we say such spaces are ‘continuously constituted’ by dwelling entrances, and that the houses have good ‘intervisibility’) are completely free from both burglary and car crime. Once again we see that crime migrates to those parts of the layout where space is visually broken up, and with least potential movement (Figure 5). Some, but not all, cul-de-sacs and footpaths are particularly at risk, mainly those where space is relatively segregated. Cul-de-sacs which are more linear and ‘well constituted’, are safer…

…The evidence we have so far suggests we should move on from the universal cul-de-sac, with through streets only as a necessary evil – a layout with frightening implications for the future of the public realm of our towns and cities – and go for integrated and ‘everywhere constituted’ street and road networks, with constituted linear cul-de-sacs directly linked to the through streets for the sake of variety and choice. We must begin to design the connecting tissue of our cities again, and populate it with those who choose its lifestyle.

…In remarkably interesting study, Tim Pascoe of the BRE asked burglars which type of space they preferred as targets. Many, it turns out, liked small cul-de-sacs, especially if they were visually broken up…

Laurence Aurbach scrutinizes cul-de-sacs in “Connectivity Part 5: Neighborhood Crime” (2007):

Researchers look at the configuration of a cul-de-sac, the placement of homes within it, and its connection to the larger-area street network. Those are some of the factors that make a difference in crime rates.

In general, the hot spots of crime are the locations with low pedestrian traffic and low visibility of homes and entrances. Hidden or partly visible homes, on long, curvy cul-de-sacs that are part of a dendritic (i.e., “tree-like”) network of thoroughfares, have the highest crime rates.

Conversely, the safest locations are on well-connected streets with plenty of foot traffic and many highly visible dwellings. The safest cul-de-sacs are short and straight, with many highly visible dwellings, and connect directly to through streets…

Segregated footpaths that connect cul-de-sacs — the classic Garden City formula — can be highly vulnerable to crime if they are secluded…

Aurbach quotes from Hillier’s 2004 paper, “Can Streets Be Made Safe?”

At the level of the overall layout, we can say, fairly unambiguously, that reasonably regular street layouts with fairly large blocks (to structure movement and reduce unnecessary permeability) are best… If such a layout is then interspersed with simple linear cul-de-sacs directly attached to the through street, then the cul-de-sacs may well be the most secure parts of the layout — but only if the street system is there in the first place to keep the cul-de-sacs simple and linear.

So a layout works as a whole. We cannot isolate elements and say that this is good and that is bad. It all depends on how the elements are put together in themselves and how they are combined to form the overall layout. Although pickpockets need busy streets, and muggers locations where integration turns to segregation so that victims are available one at a time, it is clear that what burglars — and to a lesser extent car criminals — need is secluded access. The less we provide it either by breaking up layouts into poorly used, low visibility public spaces, or creating secluded secondary access to premises, then the more difficult the burglar’s job will be…
…there are no burglaries on the first lines of sight into cul-de-sac complexes from the through roads. The burglaries are dispersed, but are usually found in the deep parts of cul-de-sacs, and most of all at the end of the cul-de-sac…

An article by Hillier for Planning in London (PDF, 2004) adds this insight:

In this area, we can see that in each and every case, the burglar gained access to the dwelling not from the cul-de-sac itself, but from the network of footpaths that surrounded the dwellings at the back and side. The lesson is then about secondary access to premises through footpaths, not about cul-de-sacs.

Based on the foregoing, Northern Avenue has several aspects that likely improve its safety:

  • It is linear
  • The homes are well-integrated with good intervisibility
  • It is well-connected to a main road (North Street)
  • You can stand on North Street and see down to the end of Northern Avenue
  • Access to the rear of homes on Northern Avenue is relatively restricted
  • Homes line both sides of the street

By contrast, the cul-de-sacs in Kohl’s latest condo proposal give reason for concern:

  • The roads would not be straight
  • The space would be visually broken up
  • The homes would be isolated from North Street
  • Many units would be difficult or impossible to see from North Street
  • Footpaths (shown in pink) and the woods would give easy secondary access to the units
  • Homes would only be present on one side of the street

In fairness to Kohl, the risk of burglary to the condos would probably be offset somewhat by the fact they are grouped into units of 2-5. This is not a unique advantage over Northern Avenue, however, as two-family homes are prevalent there and presumably confer a similar increase in security. Condo associations do present special risks, however, especially in economic downturns. Empty units can lead to a budget crunch for the association. Pressure to generate income from units can induce landlords to rent to disruptive tenants. Common spaces and infrastructure, such as stormwater basins, may be neglected because responsibility is diffused and there is a general desire to keep dues low.

Bottom line, the proposed road layout in Kohl condo proposal “D” presents new reasons to be concerned about this project. It raises security issues and reinforces its disconnection and disharmony with the surrounding neighborhood. It is easy to imagine that neighbors would feel uncomfortable walking through the roads and paths of the development. Instead of public ways, these would feel like private spaces.

See also:

Smart Growth and Crime
…[Newman’s] 1972 book Defensible Space…showed that the
safest neighborhoods maximized private space and minimized common
zones. Safe areas also minimized “permeability,” that is, the ease of
entry to and exit from the neighborhood or housing area…

“The larger the number of
people who share a communal space,” [Newman] found, “the more difficult
it is for people to identify it as being in any way theirs or to feel
they have a right to control or determine the activity taking place
within it.”

“Housing Choice and Smart Growth” (2002, emphasis added)

A survey sponsored by the National Association of Home Builders and the National Association of Realtors:

The survey asked
consumers to rate the importance of 11 quality of life factors. Quality
of community and neighborhood was rated very important by 80 percent of
respondents. This was followed closely by crime rate, 79 percent, and
price of home, 78 percent. Some 67 percent of the respondents rated the
size and features of the home as very important, followed by builder’s
reputation, 62 percent; size of lot, 54 percent; quality of the school
district, 44 percent; highway access, 34 percent; and close to work, 31
percent. Scoring lowest were convenience to public transportation, 11
percent, and close to shopping, 24 percent.

“Results of the Fannie Mae Foundation Affordable Housing Survey,” conducted by Hart Teeter Group, May/June 2002, cited in “Bibliography of References on Growth Controls and the Price/Supply of Housing/Land”, available at the website of the National Association of Home Builders (MS Word document, emphasis added)
What people want in a place to live: Low Crime Rate 67%; Stable Jobs 53%; Schools with Good Test Scores 52%; Low Taxes 50%; Affordable Homes 45%; Schools with Smaller Class Sizes 41%; Short Commute to Work 30%; Single Family Detached Homes 24%; Bigger Homes 13%. Property Crime Rate Comparison (as of 4/12/09)
Northampton: 29.88 per 1,000 residents
Massachusetts: 23.82 per 1,000 residents

Video: Second public “in-process” presentation and feedback session for Design Northampton Week

Condo Monotony: The Future of Ward 3?
To maximize profits, the developers have shoehorned units into their
lots with little regard to the preexisting appearance of their
neighborhoods. The developments feel inward-facing or ‘withdrawn’, not
part of the regular street fabric. These aspects are probably what
prompted the “carbuncle” comment from the planning board member.

EPA: “Mosquito proliferation in stormwater ponds is a concern”
Mosquito proliferation in stormwater ponds is a concern, especially
when so many wet and dry ponds are in place and continue to be
installed across the country. Many ponds are not properly maintained,
particularly in cases where they are installed in subdivisions and
other developments where the entity responsible for long-term
maintenance is not clearly defined once the construction is complete…

New York Times: Downsides of Owning a Condo in a Downturn (5/15/08)
When people buy condos, they expect their monthly fees will cover many
of the responsibilities that they would otherwise have as owners of
single-family homes, like cutting the grass and paying the water bills.
Now many find themselves nagging each other in the hallways to pay
their assessments and adding special fees while haggling over chores…

“…your fate is tied to 50 or 100 other people who may stop making
their condo payments,” [says Sam Chandan, chief economist at the real
estate research firm Reis]…

Sales of existing condo units were down 26 percent in March from a year
earlier, compared with an 18 percent decline for single-family homes,
according to the National Association of Realtors.

hunters say they are reluctant to buy into a building even when the
upfront cost seems low because they might have to pay unexpected fees
as distressed neighbors default on their mortgages or just stop paying
the association fees that cover everything from taxes to pool
maintenance to air-conditioning repair…

The shabby condition of some condos means potential buyers insist on especially steep discounts on foreclosed units…

Buildings with few units can suffer even if it just one owner falls into trouble…

[Condo owner Mark Mills] resents neighbors who have rented units they
cannot sell to 20-somethings, who leave beer bottles in the lobby and
hold late-night parties…