A New Kind of Intersection Could Help Tysons Traffic

Northern Virginia boasts the state’s first modular roundabout — a new traffic management technology that could become part of everyday life in Tysons.

Drivers venturing out to Annandale might have noticed something unusual at the intersection of Ravensworth Road and Jayhawk Street. This avian-named crossing is home to Virginia’s first-ever modular mini-roundabout, a new type of intersection design that could see much more widespread use across the region, including in Tysons.

Before last May, the intersection had only had stop signs on Jayhawk. But traffic was increasing, and cars turning from Jayhawk onto Ravensworth were having to struggle to turn enter the road safely. The Virginia Department of Transportation (VDOT) decided they needed to do something to keep cars moving.

“The primary purpose of the roundabout was to allow side streets to have safer access onto the main road,” explained Terry Yates, Assistant Transportation and Land Use Director for VDOT in Arlington and Fairfax Counties. The goal was achieved: the time that cars spend waiting to turn onto the main road has dropped by almost 90%.

They could have installed traffic lights, which would probably have cost around $600,000. Or they could have installed a conventional concrete mini-roundabout, probably around $300,000. The concrete mini-roundabout would have both been safer for pedestrians and minimized the effect that pedestrians have on vehicle traffic compared to a full-scale roundabout or a traffic signal. Dr. Wei Zhang, researcher for the Federal Highway Administration, noted that the roundabout design (whether modular or concrete) “cuts down the exposed crossing distance for pedestrians by 75%.”

For a long time, those were the only choices. But the new modular mini-roundabout is unique because it is made out of a special plastic rather than concrete. That gives it a number of enormous advantages.

First, it brings down the cost — tremendously. This design cost only $137,000 of VDOT money, although it would have been a little more expensive without materials donated by the Federal Highway Administration.

Second, installation is easy. Setting up the intersection took only two weeks, slightly less than a comparable non-modular project in Vienna. There were no impacts on utility lines or right-of-ways, and only minor impacts to the pavement.

Third, it’s eco-friendly. The plastic material is made from recycled milk jugs, reducing not only costs but also pollution. That environmental friendliness doesn’t come at any kind of cost to effectiveness: the material in question is durable and strong enough that it’s used industrially for railroad cross-ties.

The design is still experimental. In fact, the first such modular mini-roundabouts anywhere in the country were only built about two years ago in Georgia. As such, VDOT is keeping a close eye on the project. Yates explained: “We are monitoring it about every 4 months. We discuss its performance with Fairfax County Police, Fairfax County DOT, Fairfax County Government and internal VDOT sections.”

The solution isn’t perfect: VDOT has yet to develop a snow-removal procedure, and some drivers complain that the design is difficult to see at night.

Although the roundabout was built to be easily removed, Yates clarified that it “may not be temporary.” If the design continues to function as effectively as it has for the past ten months, there’s no reason it shouldn’t stay as it is — and no reason why it might not be emulated elsewhere, especially in Tysons.

In Tysons, VDOT owns and maintains most roads, meaning they could easily replicate this success. Dr. Zhang has said that “transportation departments may be able to consider similar modular roundabouts as an option where safety and congestion improvements are needed quickly.”

With Tysons slated to grow to 100,000 residents and 200,000 jobs in the next thirty years, this cheap, safe, effective intersection design could be coming to local streets in the near future.