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Place-Making Innovative Intersections

Want an economically vibrant Complete Street?

It’s a lot more possible than it used to be thanks to what we call “Place-Making Alternative Intersections.”

Engineers want to reduce congestion. Planners want to create walkable Activity Centers.  Historically, if one side wins, the other side loses.  Win-Lose / Lose-Win infighting means nothing will happen for years.  When something finally does happen, “Place-Making” may amount to nice streetlights and a few rinky-dink trees, half of which die quickly from neglect.

Here’s how Place-Making Intersections create Win-Win:  They reduce traffic signal delay, which makes it possible to also reduce speeds via traffic calming and Place-Making.  The result is that maximum speeds are slower and safer as drivers enter your fantastic mixed-use district.  But despite being slower, drivers still get from A to B a little faster due to less signal-induced delay.  Win-Win!

What can you learn here?

Alternative Intersections are “coming soon to a theater near you.”  But in many ways, it’s the same old plot line with the same auto-oriented outcome. Engineers see congested arterials, caused largely by complex 4-phase traffic signals. The four phases are: 1) EW left arrow; 2) EW through lanes; 3) NS left arrow; 4) NS through lanes.  These “left arrows” are required for left-turn safety, but they also take quite a bit of time to serve a minor portion of traffic.  How to reduce congestion?  Add more lanes – either more left/right lanes or more through lanes, since you can’t reduce the number of phases.

Or can you?  Turns out it IS possible to reduce signal phases. Continuous Flow / Displaced Left Turns (CFI/DLT), Median U-turns, RCUTs, Diverging Diamond Interchanges – all of these create more “green time” by reducing the number of phases at the primary intersection. But “traffic engineers” are very much in the habit of hardscape for traffic.  They do not think about reduced delay as an opportunity to also reduce speed limits by introducing street trees, narrowing traffic lanes, and other strategies for traffic calming and Place-Making that can catalyze walkable mixed-use activity centers.

It doesn’t have to be this way.  The movie can have a win-win happy ending.  This site reveals key strategies to achieving win-win. There are three basic “design families” of Alternative Intersection designs explored here:  1) Quadrant Intersections, 2) Thru-Turns (which encompass Median U-turns, RCUTs, Bowties, and roundabouts), and 3) One-Way Split Intersections.  See links to these topics below.

Finding new ways to shake hands

Quadrant Intersections

Quadrants redirect left turns to secondary intersections where traffic is easier to manage using a backway path.   Since former left-turn lanes are no longer needed, the can be converted to planted medians, pedestrian refuge, whatever you want!

Thru-Turn Intersections

“Thru-Turn” is a catch-all phrase for designs with names such as Median U-turns, Bowties, Restricted Crossing U-Turn (RCUT), Super-Street Intersection (basically same as RCUT), and even roundabouts.  The basic concept of a “Thru-Turn” is that you can convert left-turns into “Right-U-Thru” or “Thru-U-Right.”  A lot of potential with this design family.

One-Way Split Intersections

One-way streets are often criticized as bad for walkable development in historic downtowns. Maybe so in some specific situations, but when it comes to retrofitting huge suburban “Stroads” – it is hard to find a design with more to offer for the reinvention of dead malls as struggling retail areas.  It is often possible to convert a single huge arterial with double-left turn lanes into two one-way streams that are far narrower, slower in maximum speed, and much more people friendly – but at the same time NOT slower in terms of how long it takes to get from A to B.  Two crossing one-way pairs creates four very small, people-friendly intersections.  We sometimes call this format a “Town Center” format because it is a great platform for expanding the amount of land that has great access and good visibility – essential ingredients for creating a true “Town Center” or “Activity Center.”

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StreetPlan.net is a a free Complete Street cross-section design tool sponsored by my company, Metro Analytics, where you can easily create cross sections like those shown above. StreetPlan uses “red/yellow/green” to guide you through context-based best-practices for walkable streets supported by the Institute of Transportation Engineers, Congress for New Urbanism, and National Association of City Transportation Officials (ITE, CNU, and NACTO)

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