Solving my cul de sac quandary

I recall industry and planning events in the 1990s where someone was advocating new urbanist ideas in the early days of that movement about street network design with modified grid patterns etc over the typical post war car oriented design of curvilinear streets and lots of culs de sac – what I think of as the “spaghetti suburbs”. You know, like this diagram from Better Cities that has done the rounds on social media: 

 

Anyway, often at those events, a hard headed traditional developer challenged those ideas. What stayed with me was their claim that people want culs de sac (look, I can be old fashioned about language, but that is the correct way to spell the plural, okay!), and that was what sold. 

That point resonated with me as a lot of people do value living in those streets, and I knew quite a few people that ars very clear on the benefits they found in it.  Since then I’ve encountered other related arguments, even from CityLab.

Now maybe I’m a bit slow, but it just dawned on me why that is. The lifestyle a cul de sac offers is in fact reinforcing of why the new urbanist approach to street design makes sense. In the car dominated spaghetti suburbs, most streets that aren’t a cul de sac are designed to carry more traffic, and try to use things like curved road profiles, and maybe “traffic calming” devices, to (mostly unsuccessfully!) moderate traffic speed. Those streets aren’t comfortable for people, and the cul de sac offers a peaceful alternative in that environment where fast moving traffic is removed, so the cul de sac street is a lot safer and becomes more people oriented as people feel safe to use it for other things – walking, talking, even kids playing on it. That in turn creates more sense of community and social connection. In those suburbs, that’s where the street parties happen.

  
And of course, the whole point about the new urbanist approach is to achieve those same outcomes in most streets. To design them to slow traffic, to make them safer, to encourage more social interaction and to allow people to use the street for purposes other than driving a car. I particularly like the work of local Brisbane’s David Engwicht on this topic. 

So, it took a while for the penny to drop for me, but I have now solved my cul de sac quandary. They are popular in car oriented street designs because they are a haven in those suburbs that people like for all the same reasons we want shared streets and slower, safer street designs!

Of course, there are other reasons why developers like spaghetti suburbs – they use less area than grids for streets. And there are also lots of good reasons why they aren’t good for communities, like the lack of creating good pedestrian and cycle connectivity, as the diagram above shows, and the social and health impacts that causes. This is well demonstrated by the work of Larry Frank.

And newer design concepts have merged, like the fused grid, that try to bring the benefits of both approaches together.

And that is all of great interest, and is advancing how we design cities. But I’m glad I finally sorted out my cul de sac quandary so I can put that to bed and get on with helping create better cities!

Greg Vann
May 2015

Discussion:

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  1. Julie says:

    Dear Greg,

    I’m so pleased that you also have a cul-de-sac dilemma. I too battle with the planning ethos that they are not best practice but I have lived in two over the last 10 years! Mind you I did not look for a cul-de-sac, it was just coincidence that it turned out that way and indeed in the older parts of Mackay where I live culs-de-sac are not common at all.

    The current cul-de-sac is the largest I have ever seen. Council’s engineers must have been anticipating retrofitting for b_doubles 30 years ago? Not sure, but it’s size makes for fantastic road-based fun which our neighbourhood has extended to include a green machine, BMX, golf carts, scooters, rip sticks, bikes and skateboards. We also have handy, jump platforms, pots of road chalk and a battery operated set of traffic lights! These road fun experts also confirm that cul-de-sacs must be of asphaltic concrete (hot mix) finish to maximise road fun. Older and rehabilitated streets with tar and two-coat seal will not attract this type of fun as the gravel rash potential is just too scary!! (things you learn hey!)

    I have taken a photo of our street and the junior mad-max clan for you. There are 11 in all. After this photo was taken on Sunday arvo I stood on the road watching the kids with my wine and was joined by other parents and we chatted for half an hour until it was dark. We traded camping stories with number 8 and reinforced to Naomi at number 6 that when her 4th bub arrives next month that the street was full of babysitters as her family is in Victoria. Indeed my girls babysit for number 1. Number 5 saves their scraps for my chooks and number 7 grows bananas which he brings over and I turn into cakes and send back. The retiree in the unit next door to me mows my lawn when he’s bored. It’s our little community.

    However it is a segregated community and has no access other than a blind cul-de-sac. The fruit shop and bottle’o is about 200m as the crow flies but 600m to walk. The botanical gardens as well, would be just across the road if there was a pedestrian access at the end of the cul-de-sac.

    The problem with cul-de-sacs is that sometimes there are just too many and they are not designed with the purpose of enhancing design but rather to benefit short term gain. Land is frequently marketed at much higher values if deemed “private” and coupled with lower construction costs cul-de-sac lots present a lucrative form of development. Many I have seen purposely deny any access to reiterate the privacy attributes of the street. A high number of culs-de-sacs compromise overall community fabric, legibility and connectedness.

    Good cul-de-sac design is connected and accessible and compliments the overall estate design and does not segregate. The previous cul-de-sac we lived it at South Mackay was long and straight and I don’t think that there would have been any difference in our interaction with the neighbours if it were a through street because it was only a 6m wide pavement (enter David Engwicht) but it may have been hampered by any increase in traffic. It was connected at had with a walkway and in turn to a bike path and about 300m to the local park. That access gave direct bike and pedestrian link to the major arterial.

    Thus, I think that the conclusion is the purpose of the cul-de-sac determines its compatibility with planning tenets: is it to calm traffic, make safe the streets, encourage engagement but simultaneously enhance connectedness and encourage walking and exploring? Or is it to enhance land values and isolate enclaves of the community in the name of personal privacy?

    In the big picture numerous cul-de-sacs make retrofitting suburbia problematic in the future. From an assessment perspective, they produce odd lot shapes resulting in landowners requiring set back concessions on built form or demonstration of building envelopes. Some produce rather large lots which are difficult to support for multiple dwelling activities based on land size because of narrow frontages, wheelie bin issues on bin day and parking (yep – all the mundane stuff that really annoys residents!). The designs often require more complex infrastructure solutions multiple easements for odd utility alignments and inter-allotment drainage, especially ones which do not provide connection corridors.

    An option is this design below which I really like. The street network is regular loop network with alternate loops having only stub driveways. This limits traffic but enhances accessibility and provides good opportunity for interaction.

    So, I guess I’m comfortable in my cul-de-sac because I embrace its benefits but I am highly cognisant of its dangers to the greater community as well.

    Cheers Julie
    Photos wouldn’t work so I’ll tweet them for ya