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Transect - Dallas - wikipedia

Dallas, TX: can you identify the transect zones visible in this picture? image: wikipedia

If you’ve ever driven fifty or miles in any direction away from downtown Atlanta, then you’ve experienced firsthand the central concept behind the form-based codes devised and promoted by the New Urbanist school of planning: the Transect. The concept is so central to New Urbanism that it’s rarely discussed in detail at meetings and in presentations, preventing the uninitiated from reaching a critical level of understanding. Let’s take a moment to dive into the Transect so you can do more than nod your head and smile at the next CNU meeting.

The drive from Atlanta to my parents’ home outside of Charleston, South Carolina is a relatively mundane five-hour trek – or much longer if you hit rush hour traffic. With Atlanta’s downtown skyline in the mirror, intown neighborhoods along I-20 give way to sprawling suburbs, which eventually dissipate into rolling foothills. I usually take a shortcut around Columbia through rural backroads, then back to I-26, where miles of pine trees, small creeks, and flattening topography tell you that you’re nearing the coast. More suburbs appear as you near Charleston, and if you choose the exit for downtown, your drive ends on compact, tree-shaded streets much better suited for pedestrians than cars.


The six parts of the Transect. (image: Center for Applied Transect Studies)

Voila – you’ve just experienced the full six-part spectrum of the Transect. Let’s review: leaving from an intown neighborhood like Reynoldstown, we began in the fourth transect, or T4 (the General Urban Zone), which is just outside of T5 (Urban Center Zone) and the Urban Core Zone, T6. As we drove out of the city we passed through T3, the Sub-urban Zone, and eventually T2, the Rural Zone, until we reached T1, the Natural Zone – the largely uninhabited areas between Columbia and Charleston. As we got closer to the coast we entered Charleston’s T2, T3, and T4 zones, until we ended in the compact downtown of Charleston’s T5. A city of Charleston’s size doesn’t have the T6 zone that Atlanta does, which demonstrates the primary function of the Transect system: flexibility. The Transect can be used to describe towns and cities of any size by simply omitting certain zones that are not evident. For example, a rural town may only have T1 and T2 zones, while a large city like Atlanta will likely contain all six.

And that’s it. Welcome to the club – you can now speak on the Transect like an expert. If you’re interested in learning more, head to the website of the Center for Applied Transect Research, a research organization lead by the planners and architects who developed the Transect concept. They provide an expansive and free database of images and diagrams to help educate other designers and the general public about these ideas.

Aside from offering a convenient way of describing the rural-urban development gradient, what’s the function of the Transect? For that answer, check back for the next installment of Zoning Codes 101: Form-Based Codes.

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