The Harvard Business Review has a piece this month on research by Lawrence Frank, Bombardier Chair in Sustainable Transportation at the University of British Columbia, on the effects of cul-de-sacs in neighborhoods in King County, Washington. He found that residents in areas with the most interconnected streets travel 26% fewer miles by automobile than those in areas with many cul-de-sacs. Meanwhile, recent studies by Frank and others show that the higher a neighborhood’s overall walkability, the greater the amount of walking and biking— which means a drop in per capita air pollution, fuel use, and body mass index.
The theory behind cul-de-sacs was that they lessened traffic, since they change the primary function of local streets — rather than offering a way to get anywhere, now they simply provide access to private residences. The problem is that this design inherently encourages car use, even for the shortest trips. It also limits the growth of communities and transportation options. Consider the above maps of one-kilometer walks in two different Seattle suburbs — the first, in Woodinville, is all cul-de-sacs that result in a disconnected jumble of streets with no walking or bike paths, while the second, in Ballard, offers an interconnected network of streets that provide easy access to shopping, parks, and other destinations. The argument that cul-de-sacs increase safety because they limit traffic is also misguided — the more empty and desolate a suburban (and often affluent) street is, the more likely crime is to occur. Also, it’s much harder for emergency vehicles to reach these homes if they’re sequestered in the belly of a web of disconnected dead-ends.
As more and more direct evidence piles up that these dead-end developments are doing no one any good, the cul-de-sac tides are beginning to change: Last year, the Virginia legislature passed a law limiting cul-de-sacs in future developments. And if other states see the benefits for VA – more efficient streets that are cheaper to maintain, as well as other savings from not having to widen arterial roads that otherwise were overburdened by cul-de-sacs — perhaps they’ll follow suit.
Image: Urban Design 4 Health