WMRA News
4:00 pm
Fri February 21, 2014

Activated: Zany "French" Redesign of I-64/US-15 Jct

Bad news: the unnerving experience of driving up the "wrong" side of the road for a bit.  Good news: big boosts in safety and in traffic flow. On Friday, Feb 21, Virginia's first-ever "French flip" intersection is scheduled to open just east of Charlottesville, at the once-sleepy but now overcrowded I-64 Zion Crossroads interchange.

Officially called a Diverging Diamond Intersection (DDI), the new pattern flip-flops the usual traffic lanes. The counterintuitive trick actually eliminates the dangerous need to turn left across oncoming traffic lanes. In the new layout, right turns (or sometimes, easy "one way" style lefts) accomplish everything.  Thus, the whole need for a left turn arrow cycle at traffic lights disappears. Stoplights which once needed four or six cycles can get by with just two, speeding up one's travel time considerably. VDOT's YouTube animation of how the new Zion X-Roads interchange would work explains a lot.

Though the pattern was developed in France in the 70s (example), it has been slow to spread. There are fewer than a dozen DDI sites in the USA, according to VDOT.  DDIs can improve traffic flow without eating up much additional land (as, for instance, a cloverleaf interchange would) but they can also bewilder drivers who already have difficulty comprehending the traffic roundabouts that have popped up in Virginia in recent years. A possible disadvantage is that one would no longer be able to jump on and off the Interstate at the same place: ramp design diverts vehicles far down the road and away from the onramp with few U-turn opportunities.

Increasing traffic volume from a fairly new Lowe's store, a Wal-Mart distribution hub, and a medical facility led to the multi-million dollar project which has been in the works at Interstate 64’s Exit 136 for almost a year.

UPDATE
(Feb, 17, 2014) A VDOT page reports:

New Traffic Pattern to Take Effect Feb. 21. 
On Feb. 21 VDOT will conduct an overnight traffic switch on the Zion Crossroads diverging diamond interchange (DDI) project.  Beginning at 9 p.m., all traffic through the work zone will be controlled by flaggers and police. Only through travel on Rt. 15 and right turns on and off Interstate 64 will be permitted. Vehicles wishing to turn left on and off the I-64 ramps will be redirected using short detours. VDOT advises motorists of intermittent stops and delays on Rt. 15 during the traffic switch, which will be completed early Saturday morning. Traffic on I-64 will not be affected. In the event of inclement weather, the switch will occur overnight Feb. 22, beginning at 7 p.m.

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More info from VDOT is here.