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Summary of "Placemaking Alternative Intersection" research for the North Carolina Department of Transportation.


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But first, learn more about the problem our research aims to solve.  In a word... Stroads.

The North Carolina Department of Transportation frequently hears from communities across the state expressing a desire to catalyze walkable mixed-use development along large, auto-oriented, decaying suburban commercial highways.  Such highways are increasingly referred to as “Stroads” – a street/road hybrid.  Stroads have the economic activity of a historic “Norman Rockwell Main Street.” They also have fast speed limits akin to the rural roads they often once were (45 mph+).  Sadly, once fully suburbanized, Stroads have neither the charm of great streets, nor the speed of great roads anymore, due to congestion and frequent stop lights.  

An "Anywhere USA Stroad" vs a Stroad that was successfully converted to a "Complete Street" (Lancaster Blvd, Lancaster, CA)

Unfortunately, even with plenty of funding, it is almost impossible to convert a Stroad into a “Complete Street” that has impressive street trees, bike paths, transit, on-street parking, and pedestrian-oriented features that can catalyze walkable development.  

Why is it nearly impossible to convert Stroads into Complete Streets? 

  1. High Traffic:  Many Stroads do and always will carry huge amounts of traffic – a challenging fact for creating a walkable environment.

  2. Traffic Engineers:  Engineers worry that efforts to slow traffic to speeds safe enough for pedestrians may also exacerbate delay and congestion.  There is still a high value on drive time, even if there is also increasing desire for slower livability.  If they don't get behind your vision, you'll probably lose!

  3. Lack of Know How:  Even when engineers are on-board with traffic calming, very few know what to do - their toolbox is limited.  With so many cars, driveways, business signs, etc., finding room for street trees, on-street parking, and improving alternative modes may be extremely difficult.  They end up putting "lipstick on the pig" because it's the best they can figure out.


Thus, the main problem to solve is to discover innovative ways to manage high volumes of traffic, to the satisfaction of engineers, and at the same time create a truly transformative environment that can catalyze impressive scales of walkable development.

How suburban value is created, then lost, and how we hope to create it again.

The diagram below shows how Stroads often start as rural roads, then explode into popular "Shiny Stroads," and finally collapse into "Ugly Stroads" in economic reversal.  After collapse, many communities hope to reignite their popularity as "Complete Streets," but neither engineers, nor urban architects, nor planners know how to do much more than "lipstick on the pig."  Our research aims to empower these groups to truly transform Stroads into Complete Streets that can catalyze walkable mixed-use development.

Phase 1: Rural Road: Fast and Safe, Low Development

Phase 2: Shiny Stroad:  Development causes DOT to widen, but they also attempt to keep speed limits high.  Auto-oriented commercial overwhelms the system with lots of complex stop lights.  

Phase 3: Ugly Stroad: As the shiny wears off, businesses and residents of means flee to the next "New and Shiny Stroad."  DOTs and communities are left without tax revenue to maintain both the old and new Stroad.  But traffic engineers are happy - speeds have improved now that there's less congestion since half the people fled!

Phase 4: Reclaim as Complete Street?  This is very hard to achieve, and that is the point of our research!  We think we have some new strategies that can be effective.

Alternative Intersections:
The Core of several“Big Ideas” for solving this problem

NCDOT hired NC State University and Urban Innovators to research new strategies for making progress toward managing the high traffic volumes found on Stroads in more pedestrian-friendly ways.  The research team believes that redesigning how major intersections operate is key to accomplishing this goal. 


There are three innovate “Alternative Intersection” types that the team believes have strong potential for managing high volumes of traffic, and at the same time catalyzing walkable development:  “Quadrant Intersections, U-Turn Intersections, and One-Way Split Intersections.”  Each of these is described briefly here, followed by examples of how these could be implemented in the Greenville study area.

First, what is a “Stroad Intersection”?

Typical Stroad Intersection, TopView.jpg

Two-way Stroads almost always have 2-3 through lanes in each direction.  At an intersection with another Stroad, engineers install left-turn arrows, and often "double lefts," so lefts can be accomplished safely.  The case above has 9-lanes a pedestrian must cross - roughly 150 feet, or half a football field!  Extremely intimidating, and virtually guarantees that this area can NEVER be truly walkable and livable without a significant reinvention.  Traffic almost always drives 45 mph or faster between stop lights, even if the speed limit is 35 mph.  But the actual average speed is far slower than 35 mph due so much delay at the stop lights!

Below shows how left-turn arrows (movements 1 and 3) create a four-phase signal, which in turn limits how much green time is available for the major through movements (2 and 4).  This NCDOT research is demonstrating that Quadrant, U-Turn, and One-Way Intersections can reduce the number of signal phases.  This makes it possible to drive slower (think tortoise through a walkable environment), but also travel the same average speed if not faster due to more green time.

What is a Quadrant Intersection?

Instead of managing lefts directly at the main intersection, a Quadrant redirects those movements along a back-way path as shown here.  Notice that vehicles on the red path have no out-of-direction travel.  Those following the blue path have some out-of-direction, but even they are likely to get to where they’re going quicker due to less congestion.  Former left-turn lanes can now be converted into planted medians with trees and pedestrian refuge areas in the middle of cross-walks.  The Quadrant backway improves access and visibility for parcels along that backway, adding value to that land and making it attractive for mixed-use development.  There are many variations of this idea, such as a four-quadrant system that converts blue paths into red paths, but this diagram is a good start.

Caution:  Both Greenville and Smithfield agreed to be "Guinea pigs" for our ideas, with a caveat that none of the ideas have yet been, and may never be, vetted within a formal planning process.  These are NOT recommendations for what each city should do, (though they eventually could be after a formal public involvement process).  They are basically "free ideas," compliments of NCDOT and our research team, that each city is welcome to investigate further or reject.  For research purposes, these are simply real-world models to learn from.  This way NCDOT and other communities can determine if they'd like to pursue designs like this.

What are our ideas for Greenville?

The next graphics show how we applied some of these ideas near Greenville Mall on Greenville Blvd, Arlington Blvd, and Red Banks Road. At the right is the majority of the study area we selected, along with the Quadrant, U-Turn, and One-Way Couplet opportunities we have been exploring.

Note: The one-ways require two new streets, labeled "New SW" and "New NW".  Both traverse mostly parking lots, but likely would hit the "blue buildings."  The biggest hit is the southwest portion of the mall.  This would only be implemented in conjunction with the mall owners - when of their own accord they decide they need to reinvent their property and want to explore this as an option. 

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