One of the tenets of new urbanism is that streets should be laid out in a rectilinear grid to maximise connectivity i.e. to minimise public transport and walking distances.
This research project in Seattle seems to confirm the wisdom of that principle. It compared the distance travelled by residents of two neighbourhoods and found that in Woodinville, where the dominant street form is the cul de sac, residents travel 26 per cent more kilometres than residents of Ballard, where streets are laid out in a rectilinear grid.
As it happens, I’ve spent a fair bit of my life living on a “no through road” or similar street form and I think the advantages of cul de sacs are too often neglected. I grew up in a closed street, lived for six years in a mews and currently live with my family in a short cul de sac created in the 1950s when a larger property was subdivided into seven lots.
The great advantage of the cul de sac is low traffic. When my children were very young my wife and I were relaxed about them playing in the street because the only cars that entered the street were residents or their visitors. And for that same reason we don’t have issues with traffic noise like we used to have in North Fitzroy. These are major advantages and should not be dismissed lightly.
But cul de sacs have another advantage. If they’re not too long, they can create a sense of a place that is shared or “owned” by a small number of residents. We got to know all our neighbours well, shared child supervision responsibilities and even had an annual lunch in the middle of the road.
Some, perhaps most, older suburban cul de sacs do increase walk distances to schools and shops. This is in large measure because they are frequently too long and because the feeder roads they run off - which are often loops - are themselves overly long and sinuous.
Some inner city areas like Fitzroy have implemented the cul de sac idea more successfully. Strategically placed road closures and other devices, like having multiple one-way changes of traffic direction, deter through traffic while preserving directness for pedestrians. The fact that Fitzroy is a strict grid is incidental - it could just as easily have curves like some inner parts of Sydney and Brisbane where similar traffic calming measures have been put in place.
It is a relatively straightforward matter to provide pedestrian paths in new suburban developments in order to connect cul de sacs to other streets, while still stopping through traffic. It is also possible to have local streets that discourage through traffic but are overlain by a conventional rectilinear grid of arterial roads to provide direct routes for buses.
The new Toolern Structure Plan at Melton, for example, proposes a major street grid at roughly one kilometre centres, giving reasonable walk distances from residential areas - whatever their street layout - to direct bus routes.
There is much that is valuable in the principles of new urbanism but there’s no need to throw the baby out with the bathwater. The trick is to keep cul de sacs short, avoid long looping feeder roads and make the layout “porous” for walkers.
But what about that 26 per cent extra kilometres attributed to cul de sacs by the Washington study?
This appears to be a case of ideological blinkers because there are reasons to think this particular study is deeply flawed. In particular, the two areas studied appear to differ on much more than just their street layout. As one commenter says:
These guys need to get their facts straight. Ballard is not a suburb (although it once was a long time ago). Comparing Woodinville to Ballard is basically comparing the suburbs to an in-City high-density residential neighborhood. Ballard is more walkable for a myriad of reasons, few culs-de-sac probably being low on the list …
Socioeconomic differences would also have to be taken into account. If the residents of Woodinville are wealthier than those of Ballard that alone could explain their higher level of travel.
P.S. I know the plural of cul de sac is culs de sac, I just don’t like it.
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