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.
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?
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High Traffic: Many Stroads do and always will carry huge amounts of traffic – a challenging fact for creating a walkable environment.
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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!
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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.
This Research Creates Win-Win-Win!
Many engineers want to help create more walkable environments, but with so many cars, they don't have great strategies for that. It sets up a Win-Lose situation: one or the other, but not both.
Luckily, that is no longer the case! Because of this research, it is now possible to create great, walkable "Places," while at the same time manage high volumes of traffic in ways that will satisfy engineers.
But before exploring solutions, please learn a little more about the problem: Stroad Intersections
What is a “Stroad Intersection”?
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 it virtually guarantees that this area can NEVER be truly walkable and livable without a significant reinvention - but how to reinvent?
As the diagram below shows, Stroad Intersections almost always have 4-phase signals: 2 for lefts and 2 for throughs. This is like having too many switches turned on, and the overload "blows the circuit breaker." If you can reduce the number of signal phases, there will be more "green time," which means you don't stop as often, or for as long when you do stop.
It's exactly the tortoise and the hare story. Fast is actually slow if you stop a lot, but when you get more green lights, you can introduce traffic calming and reduce the speed limit without making drive trips take longer. This is key to political viability. We call it "Drive Slower, Travel Faster!"
Placemaking Alternative Intersections
Managing all four movements at a single intersection becomes a "tangled mess" as engineers add "double lefts" on all approaches, dedicated right lanes, and more lanes in general to deal with the inefficiency. Thus the key is to use additional intersections to redistribute these lefts.
Quadrants move lefts to secondary intersections, which greatly relieves the primary intersection. U-Turns convert lefts into "Thru+U+Right," and thus do not need left arrows. One-way streets do not have oncoming traffic anyway, so lefts do not need a special signal phase to be managed safety. All three of these designs increase local area connectivity, and they have many other pedestrian-oriented opportunities and attributes.
The diagram below shows two variants of the Quadrant, and two of the U-Turn. All variants can still create 2-phase signals if you are able to route lefts on both the green and brown.
Learn More About Each Design
For each design, the research team created a large number of Before / After diagrams along with other analysis. Click one below to learn more about it!
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.
