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Between car-centric and carfree: "Fused Grids"

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  • Christopher Miller
    To continue the thread of protocols and related issues for carfree conversion of existing urban areas, here is something interesting I recently came across
    Message 1 of 1 , Apr 5, 2008
      To continue the thread of protocols and related issues for carfree
      conversion of existing urban areas, here is something interesting I
      recently came across (via a comment on a Treehugger posting): a web
      site describing a street network concept called the "fused grid",
      proposed by Fanis Grammenos, a researcher at the Canada Housing and
      Mortgage Corporation:


      Grammenos looks at the benefits and disadvantages of both cul-de-sac
      and grid street layouts, and proposes what he calls fused grids as an
      alternative combining the advantages of both. Partly inspired by the
      street layout of old Savannah, Georgia, fused grids combine an
      overall continuous grid for walking and cycling with a broken grid
      containing cul-de-sacs that prevent automobile through traffic within
      a neighbourhood. A fused grid can in principle be constructed either
      by overlaying suburban cul-de-sac and loop layouts with a network of
      continuous pedestrian and bike paths, or by closing off portions of a
      continuous street grid to car traffic, while leaving the grid open to
      non-automotive travel.

      This looks like a useful template for the early to intermediate
      stages of gradual, phased-in carfree neighbourhood conversions,
      especially for urban neighbourhoods built on a grid plan. Clearly, it
      could also be applied with varying degrees of success to suburban
      neighbourhoods � text and links on the website refer to an experiment
      in the southwest Ontario town of Stratford �, but without extensive
      rebuilding and redensification, it's unlikely you could go all the
      way to eliminating dependence on private automobiles in such cases.

      Grammenos comes at the problem from the point of view of what can be
      done with currently existing road networks in order to shift some of
      the advantage over to pedestrians and human powered transport. From
      an email he sent me: "Ever since I became aware of the car free
      cities web site, I thought there were a lot of commonalities between
      the two concepts. One challenges people to consider a revolution and
      the other an evolution; both with the same goal - to give pedestrians
      more control. " Since his approach takes it for granted, without
      overtly stating so, that cars are and will probably remain an
      important part of urban transportation, this assumption colours his
      vision of how a fused grid would typically be constructed. For one,
      he only uses the term "street"only to refer to a route open to car
      traffic; pedestrian and cycle routes are "paths". This implies that
      they are likely narrower than streets, and his drawings of fused grid
      plans seem to reflect this assumption. It also seems to imply that
      housing would only be located on "streets" and not on "paths". This
      seems to reflect how fused grids might grow out of superimposing a
      pedestrian/cycling grid on a suburban street network. In a dense
      urban grid, shutting off streets or parts of streets to car traffic
      obviously need not imply that housing cannot exist without fronting
      on a car-centric street... Certainly, if fused grids are used as a
      tool for a phased-in carfree conversion, the ultimate aim would be
      for all residential streets to become carfree eventually. I think his
      assumptions are just an artefact of taking suburban street plans as
      the starting point for the process. Nonetheless, he does seem to
      imply � I may be misunderstanding him here � that areas blocked off
      to cars would need to lose some buildings to become "green" (i.e.
      park-like) areas, though that could in principle only apply to the
      asphalt-paved street surfaces themselves.

      One thing that does strike me in his proposals is that fused grids
      only seem to be intended for the neighbourhood level, and not to the
      overall street grid. He accepts that main streets would remain car-
      centric, providing speedy thoroughfares for automobile traffic on
      primary, mixed-use streets bounding residential neighbourhoods. From
      a carfree conversion point of view, it would be just as useful, in
      the early to intermediate stages of conversion, to apply the fused
      grid idea to the larger primary grid as well, pedestrianising
      stretches of the streets while creating pedestrian/cycling boulevards
      with unrestricted high speed public/freight transport access. Doing
      this at the larger level would bring home the message that carfree
      streets are not just for residential neighbourhoods, and ought to
      further discourage automobile traffic overall by making the
      automobile road network less convenient while at the same time making
      speedy public transit more attractive.

      As I said in my earlier postings, I am surprised that most well-
      publicised pedestrianisation efforts � Copenhagen for example, and a
      large number of other carfree areas listed on the Wikipedia page at
      http://en.wikipedia.org/wiki/List_of_carfree_places � seem to
      concentrate on shopping streets and not on residential areas. Perhaps
      it is time to take a second look at how protocols could be put in
      place for much more ambitious phased conversions of existing urban
      areas to carfree status, something that I am sure will finally find
      its place on the public agenda in the not too distant future. For the
      typical North American city, an extended fused grid approach would be
      a very useful tool combined with the kinds of proposals Joel has
      already put forth. When the time comes that governments finally see
      the usefulness of moving to car-lite and eventually carfree cities,
      it will help a lot for this kind of work to be available as a
      template to consider.

      A few more comments about the fused grids site:

      - the web site has links to various papers, not all free access, as
      well as to the Carfree Cities web site among others
      - one paper compares grids with radial designs, which are overall
      preferable for pedestrians; putting something like this in place
      would require some rebuilding near the middles of long blocks to
      allow the construction of sottoportego-type archways leading to
      shortcut paths through the middles of such blocks. For illustration's
      sake, the typical residential city block in Montreal is 500 metres
      long on its long side compared to merely 100 m on its short side.
      Shortcut routes through the length of a block at somewhere around 150
      and 200 m from either end could help to reduce walking times
      considerably by making walking routes less circuitous overall. This
      might be one way a fused grid could be put into practice, beyond just
      shutting off streets to automobile access.

      Christopher Miller
      Montreal QC Canada

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