The Roanoke Times

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• What do you think about the new left turn signal? Comment on the SWoCo blog

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• Learning curve at the roundabout circle

Interactive game

Using a four-way roundabout

• Try your hand in a roundabout with this fun interactive game. Use caution, and don't cause a wreck

Southwest Roanoke County is once again the proving ground for new Virginia Department of Transportation technology.

Some drivers are still getting used to the 9-month-old roundabout merging traffic on Penn Forest Boulevard and Colonial Avenue.

Now, just about a mile down the street, drivers will have to negotiate the region's first "permissive left turn" traffic signals that use flashing yellow arrows.

The new lights govern left turns off Chaparral Drive at Penn Forest. They were activated Wednesday afternoon.

The flashing yellow arrows -- indicating a driver may turn left after yielding to oncoming traffic or pedestrians -- "are more effective than the more common circular green light," said VDOT spokesman Jason Bond.

"Studies have shown that after a short learning period, flashing yellow signals are better understood, better obeyed and are safer," he said.

Drivers who want to turn left will see four arrows indicating traffic flow.

The top red arrow means to stop; the second steady yellow arrow means the light is changing; the third from the top is the flashing yellow arrow, giving permission to turn after yielding; and the bottom green arrow means the driver has the right of way to turn left.

The system is becoming the national standard for handling permissive left turns, Bond said, although Virginia is just now beginning to experiment with it. The only other Virginia location for the lights is in James City County at the entrance to Busch Gardens.

A YouTube video of traffic there is available online.

Bond said having the new roundabout and new lights so close together was purely accidental.

In searching for a site to try the new light system, "we were looking for a location with a relatively low speed limit, and one that was not real large or spread out -- not a primary route." The speed limit at Penn Forest and Chaparral doesn't exceed 35 mph.

Bond also noted that the site was chosen not because it has a high number of accidents, but because it was a good candidate for smoother, more efficient traffic flow.

Bond said engineers will likely be at the site watching traffic for a day or two and after that will keep an eye on it through temporary traffic cameras, just as they did at the roundabout.

The next such light may go up somewhere on or near the Virginia Tech campus in Blacksburg, Bond said.