What’s the clear zone? And why you should care.

Clear zones in urban areas are an example of misapplying highway standards to urban streets.  High speed roads serve an important purpose: Connecting point A and point B quickly and safely. In this environment, it is desirable to forgive the mistakes of drivers by providing a clear zone which allows a recovery area in which to avoid a collision at speed.

The problem arises when this tactic is misapplied on urban streets. On an urban street, we welcome people on foot, on bike, skateboard, Segway, baby strollers…You name it. It’s a complex environment and its purpose is economic exchange and social interaction (to name a few of many purposes), not merely moving cars, which is secondary. James Howard Kunstler provides perhaps the best definition of what an urban street is at its best in his classic and provocative TED talk:

The public realm in America has two roles: it is the dwelling place of our civilization and our civic life, and it is the physical manifestation of the common good. And when you degrade the public realm, you will automatically degrade the quality of your civic life and the character of all the enactments of your public life and communal life that take place there.

The building blocks of our public realm – streets, squares, plazas, parks – depend upon civilized behavior by all participants in order for civilization to flourish. In this environment, cars need to move slowly, not just for safety of the people not in cars, but in order for community itself to be able to flourish. Imagine some of your favorite public spaces: A square in Savannah. Duval Street in Key West. Clematis Street in West Palm Beach. Central Park. What’s common about all these places? Cars are secondary to people – the dominant species in these environments are the people walking, talking, and playing – and cars are welcome too as long as they behave.

The misapplication of clear zones to urban streets, boulevards, and avenues (and yes, those words mean something rather different than modern traffic engineers would have you believe) leads to degradation of our urban spaces: Chopping down trees in the right of way for purposes of line of sight (such as the row of oaks featured in this blog post), removing ‘fixed hazardous objects’ (FHOs, they’re called in traffic engineer parlance) such as benches and street lights. While this approach makes complete sense in a high speed interstate or highway environment, it is disastrous in our neighborhoods, where we want people and slow speeds.

More from Andy Boenau of the excellent podcast Urbanism Speakeasy and the producer behind Walk Lobby. Andy is a Civil Engineer and AICP planner working to make streets appropriately designed for people. Andy produced this funny video to explain clear zones to the average Joe.

#SlowTheCars #SlowStreets


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  1. Important writing, Jesse. Thank you! Just to show how things have improved, I designed sidewalks and street lighting for a residential neighborhood that lacked those amenities about 5-years ago. I wanted to include street trees in the design, but an engineer convinced everyone that trees would violate the clear zone requirements of the FDOT Green Book. Those Live Oaks would be looking great right about now.

    • How shortsighted of them. Without street trees in residential neighborhoods, the neighborhoods cease to be functioning neighborhoods in many ways. That’s how important I’d characterize street trees in most residential American settings.

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