September 19, 2016

Those Unsafe Suburban Curving Streets

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The Business Insider has a compelling article about the street grid. For millennia we designed and developed the street grid as the most functional way to develop a place.

Emily Badger with City Lab confirms what we always suspected. While going to the suburbs for a “safer” life,  people have actually been going to suburban communities composed of curving street plans that “ make us drive more, make us less safe, keep us disconnected from one another, and that may even make us less healthy”.

A key part of the  20th century Garden City movement and the development of the Radburn Plan for suburbs in North America was discarding the grid pattern and going for organic, round street shapes.  Norman Garrick and Wesley Marshall started researching street network designs  commencing with bikeable Davis California. Even though Davis has more than 16 per cent of the population biking to work, it also has the lowest traffic fatality rates in the USA. By looking at the data of over a  quarter of a million crashes in 24 California cities over 11 years, these researchers discovered that “the safest cities had an element in common: They were all incorporated before 1930″.  And they all had the grid pattern.

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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,” Marshall says. “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.”

The researchers also found out that people who live in curvilinear suburbs versus grid pattern suburb spend 18 per cent more time driving  and have less contact with local shops and services. Grid cities have better connections for walking and biking, and with less car crashes, are safer.

Cul-de-sac roughly means bottom of the sack in French.Time to reorder and get back to the grid.

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  1. Hilarious. Reminds me of the scene in the Truman Show where our hero goes into a travel agency to get a ticket for somewhere else and sees a poster of a plane being hit by lightening and the words “IT COULD HAPPEN TO YOU!” So, grids are safer. Yes, perhaps, but who cares? The people who choose to live on curving streets (Shaughnessy comes to mind, or the Endowment Lands or British Properties, or West Vancouver generally) do so because they like them, as you can see from the fact that those are some of the most expensive places to live in Vancouver. I’ve lived on gridded streets that were the dreariest experiences of my life (Kitsilano, btw, where the most active people in the neighbourhood were the dope smokers on the balcony across the street).

    1. If they like them because they are ‘safer’ … doesn’t it mean it is a good piece of information to know that they are actually less safe. I think since the perceived safety of such places is used as both a selling feature, and a reason why they are espoused in general, that information that might serve to disabuse some of their notion of perceived safety is a useful thing. I’d prefer to live somewhere safe than ‘safe’, all things being equal.
      Does that stop me from liking curvey streets, no, does this mean that curvy streets are verboten, no, the safety difference comes largely from the extra driving time, the less walking ability, and the higher speeds typically associated with cul-de-sacs, simply making a curvy grid does none of these things.
      You can have gridlike cul-de-sacs just as easily as you can have curvy grids, it doesn’t mean that a, orthogonal cul-de-sac is safer, just that it uses right angles.

  2. Don’t most old towns and cities have curvy streets? Better connected than suburban cul de sacs of course. The military style grid is better for walking than cul de sacs (without path connections), but it’s pretty boring. There are more street patterns than suburban cul de sacs and straight grid.

  3. People aren’t rational and will fight the math at every turn. They will fight it because to admit the math is right is to admit they’ve been wrong the whole time. And most people think they’d rather be dead than wrong. Unfortunately this isn’t news.

  4. Efficiency might favour the grid overall (and maybe more for the private vehicle model of transportation than for others), but in terms of where i’d like to live I’d choose something between grid and suburban patterns – a non-gridded system that still connects.
    Grids can be oppressive and they completely ignore the topography, one more thing in a long list that separate us from the natural world. When I first came to this city I was struck by the contrast between a place so connected to its natural environment and yet organized on an unrelenting street grid.
    Perhaps the grid is unavoidable, but it would be interesting to imagine an alternate Vancouver with a street system responding more closely to the natural landscape.

    1. It took an extraordinary lack of imagination to impose the grid on the city of Vancouver. By running its main arterials north-south and its residential streets east-west the planners managed, in one thoughtless stroke of the pen, to throw half the back yards in the city into shade.

        1. The trick would have been to run the lots the other way so that yards face east-west so every house would have sun in one yard in the morning, both yards in the middle day, and the other yard in the evening. As for those like you and me who like some shade, you can make it wherever you want with as little as an umbrella. But you can’t make the sun shine where it can’t, nor can you get the dew to dry in the summer where the sun doesn’t shine so we have ended up with thousands upon thousands of cool, wet back yards where grass doesn’t grow in the shadow of two storey houses.

        2. One could easily argue, however, that by having the yard the long way north-south, that you are at least likely to have no shading from a neighbour’s tree on your yard, it doesn’t take much of a tree to create that exact cool, wet back yard if you have some dense trees to the immediate south. Also, one simply replaces cool, wet back yards with cool, wet side yards.
          My point by asking about geometry was only to suggest that every layout that incorporates relatively significant density also creates overshading, and there are always tradeoffs (and so, it isn’t as clearly ‘dumb’ to have it the way it is vs any other way).
          The thing that is kinda dumb is the RS1 envelope, which in tandem with the N-S axis lot means that anyone trying to put solar panels on their roof has half of them always facing the wrong way, by nature of the envelope shape creating a N-S axis ‘barn’ shape. This however has nothing to do with the yard, and everything to do with what we have decided should go on that yard, and that decision hasn’t caught up with a modern solar reality.

      1. There are lots of factors.
        As pointed out the entire west side of Vancouver has the sun effect negated by the existence of massive trees.
        The eastside of Vancouver – its population more attuned to the economies of planting vegetables – doesn’t have as many large shade trees.
        The best way to accomplish sunny growing yards is to plant vegetable beds on the south sides of all houses –
        i.e. plant veggies in your front yards if you are on the north side of the street.
        But I here the staff at City Hall turn up their noses at such practicalities…

  5. The part about cul-de-sac design that’s lacking is that walking and cycling are made less efficient unless there are cut-throughs to other places through. Some have them and some don’t. Many of the ones that are there are too narrow.

    1. See Houten in the Netherlands for a place which does essentially what cul-de-sacs do, but without cutting off all the pedestrian/bike links, and by doing so becomes a pretty cool place, and also safe … but these features were very deliberately added to avoid the pitfalls of the cul-de-sac.

      1. That’s what I was thinking as well. A neighbourhood could do things to discourage someone driving through it to get somewhere else yet allow walking and cycling. We have that a little bit in parts of Vancouver but it ‘s pretty mild.

        1. http://www.citylab.com/cityfixer/2015/06/a-case-study-in-bike-friendly-suburban-planning/396107/
          My uncle lives there, and I’ve been there often … pretty nice little town. There is one road through the middle with shops/etc, but otherwise to drive anywhere you need to go out to the ring, around, and back in again (think of a wagon wheel with the hub missing, and the spokes going nowhere by car, but connecting through by walking/biking). You can basically get anywhere by bike or walking about as fast as you can in a car.
          There are, of course, scaling issues, and to expand the town added another ring beside the first, but the overall density isn’t bad – napkin math says average lot is about 2500sf, which is significantly smaller than Vancouver average, for instance, so its an un-suburban suburb.

      2. It’s not just the pedestrian/cycling connectivity, though. By design, cul-de-sacs limit most vehicle trips only to residents. That means the supporting arterials and collector roads – necessary to get to these precious snowflake dead-ends – must carry heavier capacity burdens. It is on these larger roads that most serious crashes and deaths occur.
        A grid spreads and diminishes the serious crash risk over the local network. Cul-de-sacs, as they’re typically and lazily built in North America, raise everyone’s risk by requiring wider, faster, and more dangerous roads to ‘accommodate’ the limited network function of the ‘I just feel so safe’ cul-de-sac resident.

        1. I guess the balance hangs in whether the extra risk from those larger roads, balances against the extra local trips because its so easy to be a pedestrian/cyclist that most are. If the former is doubled, but the latter is doubled also, then an approx. homeostasis of risk is still achieved.
          The distinction is, as you suggest, the ‘typical + lazy’ manner here, vs the studied + data driven manner there … they study exactly what type or road is more/less dangerous, and that gets fed into future design/redesign, here it seems not-so-much. Were we also to be unlazy, then an alternative result might occur.

      3. Areas of Deep Cove, Blueridge and Edgemont in North Vancouver have cul-de-sacs with paths going through. Other cul-de-sacs were blocked with private lots for some reason.

    2. There’s a world of difference between vehicular non-through; curving streets; and cul de sacs.
      Vehicular non-through is desirable. It could terminate in a park or in a returning lane.
      Curving streets that follow the natural topography are also desirable – these are the streets that were built on top of existing pre-motordom roads where physical exertion dictated routes – shortest and easiest.
      Houses built on these typographically illogical grids are also difficult.
      Boston has a lot of these – which confuses visitors. These are Eco – logical streets. If you are building in flat Richmond grids make sense. In hilly Vancouver natural contours would have been preferable. We waste massive energy endlessly going up and down hills. But planners sat in their offices and imposed grids.
      The only significant topographically logical street in this city is Kingsway – the old wagon trail.
      In feng shui, cul de sacs are deemed inauspicious. The swirling wind energy does not settle. Houses are raked with the monster eyes of cars. They are claustrophobic. Cul de sac is a marketer’s term. Dead end street has less cachet.
      The two people just murdered at 43 Dieppe Place lived in a cul de sac.

  6. The Burnaby grid is worse than Vancouver because of its many steep short hills. The roads that follow the contour or are flatter such as Douglas are unpleasant to walk or bike. Lots of traffic, no sidewalks in some places and nothing for bikes.

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