Some people love them, others hate them. Personally, I think they are useful to maximise the lot yield of terrain dependant sites, but when used to attempt to create private roads and spaces with no regard to the form of the land, Cul-de-Sacs become pretty tiring. (If you can’t access the NY Times article, there’s a pdf of it here.

Why Some Towns Place Roadblocks on Cul-de-Sacs – New York Times:

Highly popular after World War II, the cul-de-sac is essentially a dead-end residential street, often but not always ending with a large circular patch of pavement allowing vehicles to turn around. The form was initially embraced as something that promoted security, neighbourliness and efficient transportation…

Homeowners found that the cul-de-sac limited traffic, creating a sense of privacy, while encouraging ties among neighbours, who could hardly avoid one another. Developers liked the cul-de-sac because it made it possible to build on land unsuited to a grid street pattern and because home buyers were willing to pay a premium to live on one…

…while people within a cul-de-sac may know one another well, they are less likely to know people who live on other streets. “What was lost is a sense of community,” [Michael Lykoudis, dean of the School of Architecture at the University of Notre Dame] said.

What I dislike more than Cul-de-Sacs are Turning Heads, a geometric marvel permitting a three-point-turn to be executed at the end of a street. Developers can stick one of these in and save pavement compared to a Cul-de-Sac. But what they save in bitumen, they lose in functionality. A traditional Cul-de-Sac allows vehicles to turn about without stopping or reversing, generally an 8m radius will allow for a passenger vehicle to complete this manoeuvre in one go. For an industrial subdivision, radii up to 12m or more should be considered to facilitate rigid trucks or even semi trailers.

But don’t try to convert a Cul-de-Sac or two into a through road, unless you are prepared for a fight. In one American city (Eagan) all Cul-de-Sacs are sign posted with “Future Through Road”, just so residents can’t complain that they didn’t know!

Setting guidelines on the use and abuse of Cul-de-Sacs is probably an important exercise for local governments. Here in Australia, most councils have fairly well documented Development Control Plans that include such standards as the number of intersections and the distance from all lots in a residential subdivision to the nearest collector road, and the maximum length of a Cul-de-Sac when used. It makes it easier to know what can be done, but it also creates definite loopholes that developers will find ways to exploit.

At some point I’ll post an article on the vertical grading of Cul-de-Sac heads for different conditions – One for the civil engineers and road designers.


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Published by Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada.

One reply on “Cul-de-Sacs and Turning Heads”

  1. I live in a Cul De Sac but I believe it is an unplanned one and was eventually supposed to link up paralell to the railyway line as a secondary road through Castlegar.
    In 1980 I discovered that the road, Arrow Lakes Drive, had been renamed from Woodland Drive which is still in existance today.
    It is five minutes walk to the city centre so I generally walk unless it is pouring with rain or I have my weekly grocery shopping to do.
    It certainly has its pros and cons . I like the peacefulness, but it can get a little lonely.
    When the snow comes I get more than my fair share of a really heavy snow windrow at the bottom of my driveway due to the location of a road Y-junction opposite my property as there is nowwhere much for the snow to be stacked. Also due to the fact that the snow sometimes lies on the road for a couple of days before the plow arrives trhe snow is usually made up of chunks of ice and it takes a lot of energy to move that.
    I watch the snow plough running back and forth along our littel stretch of road and feel for him when he has to stack the snow at the bottom of my driveway, I do think the drivers care but cannot do much about it.
    I think ti would do our area good to be more comemcted to the city centre, as we have to drive out toward the Celgar road then back into the city, having to mix with the slightly faster traffic for a couple of hundred metres. Coming back to our area, we have to go under the Robson-Castlegar bridge which can get very icy in a very short time, then merge into that faster traffic and then make a sudden sharp left-hand turn into our road with no room on the road for too-fast traffic to go past us.

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