Denver Urbanism: Is your neighborhood a ‘tree’ or a ‘grid?’

You may have read the article that made the rounds on the Internet a few months ago about the two houses in suburban Orlando that share a backyard fence, yet to drive from one house to the other requires a seven mile journey. If you haven’t, check that out here.

I mention this because it’s a perfect, albeit extreme, example of the failures of land development and transportation planning in suburban America for most of the latter half of the 20th Century. Much of suburbia, like the Orlando example, has been planned using the “tree” approach to how the streets and neighborhoods are laid out. Here’s what I mean:

Envision two big leafy trees next to each other in a field, with each tree representing the road network of a separate subdivision, and the ground representing the major highway to which each subdivision’s street system is connected. The tree trunk is the main entry street into the subdivision — you know, the street with all the nice landscaping and the sign with the subdivision name on it. As you proceed up this main trunk street, you’ll see major branch streets heading off in different directions. Follow any one of those main branches, and you’ll see even more streets branching off, with the streets getting progressively less trafficky as you go.

After branching deeper and deeper into the subdivision, you’ll eventually find yourself out at the cul-de-sac end of a twig, where the farthest out houses, the outermost leaves on the tree, are found. And just a short distance away are the outermost leaves of the nearby tree. They are so close, and yet so far away, because these two subdivision trees don’t connect to each other. To visit those nearby leaves from the other tree, you’ll have to work your way down all those branch streets to get to the main trunk, travel across the ground highway, and then up the other tree’s trunk and all the way out its many branch streets to its farthest out cul-de-sac twig. This is the street layout for much of suburban America.

You see the problem with this “tree” approach to subdivision design: everyone has to drive longer distances to get anywhere, bicyclists and pedestrians are generally screwed (unless they’re good at hopping fences and cutting through backyards), and traffic is concentrated at those main intersections where the trunks meet the ground.

The alternative? The grid. Street grids of rectangular blocks, the standard layout for most cities developed during the 19th and early 20th centuries (like Denver), may not have the bucolic appeal of curvy, branchlike suburban streets, but they are infinitely more efficient for allowing people to get from Point A to Point B. Pick any two historic Denver neighborhoods, say, Park Hill and Washington Park, and there are literally hundreds, probably thousands, of possible paths to traverse the grid from one neighborhood to the other. While there is still a tree-like hierarchy of local (twig), collector (branch), and arterial (trunk) streets embedded with the urban grid, the grid’s interconnectedness makes it a remarkably efficient, flexible, and resilient street pattern. It’s like hundreds of trees with their canopies knitted together in a weave of twigs and branches.

Next time you’re driving or biking or walking about town, think about the pattern of the streets around you. Is it like a tree, or like a grid?