A Diverging Diamond Eases Traffic Jams with a Smaller Footprint

Aug 29, 2016

The New River Valley is slated to be one of the fastest growing areas in the state. So transportation experts are getting creative about how to move traffic more efficiently and safely going forward.   As Robbie Harris reports, the Virginia Department of Transportation is trying something new in Blacksburg, near the Virginia Tech campus, where traffic tie-ups are already a problem.

  Take a virtual test drive of the Diverging Diamond

Jason Bond is a spokesman for VDOT.

“There’s a new interchange configuration that will be put in at the intersection of Southgate Drive and Route 460.

That’s where the interstate meets metro Blacksburg at one of the main entrances to the Virginia Tech campus. 

“ It’s called a ‘diverging diamond interchange’ and this type of interchange allows for more efficient flow of traffic and a smaller footprint as far as the amount of real estate or right of way that it takes up.”

The name diverging diamond comes from the ramps on and off the main highway, which describe a diamond shape.  And it’s becoming transportation experts’ preferred improvement over the cloverleaf. It became popular in the 60s when there were fewer cars and perhaps more patience with traffic than there is today.

“Another reason for this project was to eliminate the one traffic signal for a 37 mile stretch of route 460.”

That’s right, the only traffic lite on this stretch of still mostly rural road will go away. When the project is finished instead of what we call an ‘intersection’ there’ll be something we will then call an ‘interchange.’  It’s designed to create a seamless route of crossing an roadway without the need to make that dreaded left turn crossing traffic.

“It’s basically shaped like an ‘X’ configuration and it requires that drivers temporarily drive on the opposite side of the road from what they’re used to.”

Credit VDOT

You’re not actually on the wrong side of the road, and no cars would be coming at you from the other way, but because that X replaces the light it might seem that way.

And right now it may be hard to visualize because all you can see at the construction site on 460 is what looks like to two walls of Hokie Stone, that iconic colored rock quarried in this region that decorates Virginia Tech’s campus.

“That is your piers for the bridges that’s going to be crossing 460 and beams will be set on top of that, the deck put on top of that then. And you can see the Hokie Stone at the bottom there; the pattern.”

Actually Project Inspector Doug Webb explains, it’s not real Hokie stone, it’s one solid structure that has been etched and will have color added to look like the stone. But it will stand up to the wear and tear of some 34 thousand cars that already drive this stretch of Route 460 every day.

“Daily the traffic trying to get in and out on Southgate backs up hundreds of feet it’s quite a congested area.”

Mike Dunn is transportation planning engineer at Virginia Tech

“Improving the traffic for the daily traffic should help the major events as well.”

“So yes, the new traffic pattern is expected to help with that massive exodus you see after sporting events but spokesman Jason Bond it’s not only for those reasons that VDOT is redesigning this roadway.”

“We don’t design new roads to accommodate peak traffic volumes during special events. That would be like designing interstate 81 or a different project to accommodate ‘Black Friday’ traffic. But with a diverging diamond interchange, it does allow options for managing that traffic off of 460 to change some of the signal timing to allow more free flowing movement to help that game day traffic get back out onto to 460.”  

The diverging diamond interchange in Blacksburg won’t be complete until 2018. Right now there is only one in Virginia, at route 64 in Zion crossroads west of Richmond.  A second one will open soon in Roanoke near the Valley View Mall.