Are cul-de-sacs a dead end?Posted: September 22, 2011 Filed under: Planning | Tags: cul de sac, new urbanism, permeability, Toolern, walkability, Wesley Marshall 8 Comments
The New Urbanism hates cul-de-sacs – they’re emblematic of much that’s wrong with car-oriented suburban cities, including poor walkability, low transit provision, long travel distances, “excessive” demand for privacy, and even low social capital.
I might be in a minority, but I’m an admirer of cul-de-sacs. They’ve been around for thousands of years for good reason. I grew up in what in my day was called a “dead end”, 6 km from the city centre. I lived in a terraced mews in Sydney for six years, just 1 km from the Town Hall. I now live in a seven property cul-de-sac developed in the 1950s, 8 km from Melbourne town hall.
The great advantage of cul-de-sacs is they have no through traffic, so they’re quieter and it’s safer for children to play outside on the street. As long as they’re not too long, they can create a sense of place and possibly promote greater social interaction among residents too (although it’s not clear how much of that’s due to the cul-de-sac form; to lower traffic levels; or in some cases to joint ownership of common property). It’s also a matter of no little importance that residents seem to like them.
Another claim is cul-de-sacs reduce infrastructure costs significantly compared to a grid plan. Further, they “allow greater flexibility than the common grid in adapting to the natural grades of a site and to its ecologically sensitive features, such as streams, creeks and mature forest growth”.
Cul-de-sacs are popularly associated with outer suburban developments and that’s why they get such a bad rap. However they can work in a range of urban contexts. They’ve often been used in inner city traffic calming schemes (where they’re called “street closures”). Large, higher density redevelopment projects like this one in Brisbane use what is essentially the cul-de-sac form to give access to dwellings without a street frontage. Yarra Bank Court in Abbotsford would be better with pedestrian access for residents at the far end but is otherwise a delightful “dead end”.
According to critics, the key disadvantage of suburban cul de sacs is they create a circuitous road system, necessitating longer travelling distances. This discourages walking and increases the cost of providing public transport when compared to a traditional grid pattern.
It’s true that many older suburban estates are relatively impermeable. However as inner city street closures show, it is quite easy to design cul-de-sacs that are open for pedestrians but not cars. It’s also quite simple to have a 1 or 1.5 km rectilinear grid of main roads for buses (e.g. see Toolern) with cul-de-sacs confined to “filling in” each square.
I think the main reason cul-de-sacs are demonised by new urbanists is because they’re conflated with the problems of outer suburban development. Consider this quote from Wesley Marshall, an assistant professor of civil engineering at the University of Colorado:
A lot of people feel that they want to live in a cul-de-sac, they feel like it’s a safer place to be. The reality is yes, you’re safer – if you never leave your cul-de-sac. But if you actually move around town like a normal person, your town as a whole is much more dangerous.
Professor Marshall says fatal accident rates are lower in areas with a traditional grid pattern, but he makes an elementary mistake. The traditional areas are older – they don’t have fewer fatal accidents because of their street morphology but because they’re denser, with more mixed development, more traffic and slower travel speeds than outer suburban areas. The primary “culprit” here isn’t the cul-de-sac, it’s the lower density and monoculture of the newer suburbs.
The same article says “people who live in more sparse, tree-like communities drive about 18 percent more than people who live in dense grids”. Again, that’s primarily because of differences in density. For example, destinations are further apart in outer suburbs so residents are less likely to walk or cycle. Given the article refers to the US experience, it’s possible, even likely, that differences in income between the two areas are an important explanatory factor too. At least this time the writer talks about “sparse” communities rather than specifically fingering cul-de-sacs. Read the rest of this entry »
How much growth is going to the fringe?Posted: October 18, 2010 Filed under: Growth Areas, Planning | Tags: growth areas, Melbourne 2030, Melbourne @ 5 Million, Residential Land Bulletin, Toolern, Transforming Melbourne 7 Comments
The Victorian Government set a target in its 2002 strategic plan, Melbourne 2030, that only 31% of new dwellings constructed between 2001 and 2030 would be located on outer suburban greenfield sites.
In fact, it envisaged that by 2030, the proportion would have fallen to just 22%.
This ambitious target reflected the conviction at the time that continued outward growth was unsustainable. The firm view was that a much higher proportion of growth would need to be accommodated within the existing built-up area.
The subsequent update released in 2008, Melbourne @ 5 Million, significantly downgraded the target.
Melbourne @ 5 Million “anticipated” that 47% of all new dwellings constructed over the next 20 years would be located in the fringe Growth Areas.
The new target simply reflected what the market was actually doing. There would be little danger now of getting caught out by a politically ambitious “stretch target”.
The most recent edition of the Government’s Residential Land Bulletin (March Qtr, 2010) indicates how prescient the authors of Melbourne @ 5 Million were. It shows that exactly 47% of dwelling approvals in the preceding twelve months were located in the Growth Areas.
But if you think we need less development in the outer suburbs and more in the inner and middle ring suburbs, it gets worse. Read the rest of this entry »
How dense are Melbourne’s outer suburbs?Posted: July 12, 2010 Filed under: Growth Areas | Tags: density, growth areas, Kenneth Davidson, Melton, The Age, Toolern 4 Comments
Kenneth Davidson claimed in The Age yesterday that Melbourne has 15 years’ supply of outer suburban land zoned for urban development at the world’s lowest residential densities of 12.5 to 15 houses per hectare.
Lowest in the world? I think that’s possibly a little harsh when Melbourne is compared with the outer suburbs of US cities. However what I’m really interested in looking at is what Melbourne’s supposed “lowest residential densities” actually look like. What does 15 dwellings per hectare mean on the ground?
An ideal case study is the new mixed use development planned for Toolern, near Melton. According to the Precinct Structure Plan, when fully developed it is expected to cover 24 sq km, house an estimated 55,000 residents and host businesses that provide 28,000 jobs.
This is an enormous project, covering an area around a fifth larger than the entire inner city municipality of Yarra. It is equivalent in area to a 2.8-kilometre radius circle – if the centre were Melbourne Town Hall, it would extend to Richmond Station in the east, Alexandra Parade in the north, Bolte Bridge in the west and Albert Park in the south.
The minimum average density set down for Toolern is 15 dwellings (per net developable hectare), the same as the target minimum for the growth areas set out in Melbourne @ 5 Million and its predecessor, Melbourne 2030. Read the rest of this entry »