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An Optical Illusion Might Slow Drivers

VDOT workers place optical speed bars at intervals on Lee Chapel Road in Springfield designed to trick drivers into slowing down.
VDOT workers place optical speed bars at intervals on Lee Chapel Road in Springfield designed to trick drivers into slowing down. (Photos By James A. Parcell -- The Washington Post)

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By Candace Rondeaux
Washington Post Staff Writer
Thursday, May 4, 2006

It's 9:30 a.m., and cars are whipping around the narrow bend of two-lane Lee Chapel Road near Pond Point Drive as if it's a qualifying run for the Indy 500. Bill Harrell waves at his road crew. Out comes the orange "Slow" sign, then two men break out a blowtorch and begin running the flame over flat, white adhesive markers they place at intervals on the asphalt.

About two-feet long and a foot wide, the markers are nothing special. But Harrell, a Virginia Department of Transportation traffic engineer, hopes they will help create an optical illusion that could save lives. VDOT is betting there's enough magic in the illusion that even the biggest lead feet will be tricked into slowing down.

Called optical speed bars, the plastic strips were placed yesterday at intervals that narrow from 24 feet at the start to 15 feet at the end along a half-mile stretch of Lee Chapel Road in Fairfax County. When someone drives over them, the strips create a sort of flip-book effect that makes the motorist think the car is moving faster than it is.

The illusion is also meant to get drivers' attention so they will slow down as they approach the notoriously treacherous curve between the Fairfax County Parkway and Route 123.

"This is super low-tech, pretty inexpensive, and hopefully it's a solution to speeding out here," VDOT spokesman Ryan Hall said.

Traffic engineers will collect speed data from the road and compare their findings with information collected before the speed bars were installed. If the optical illusion works in Fairfax, VDOT is likely to begin using the traffic-slowing technique on other troublesome roadways across Virginia.

Part of a larger, $100,000 project being conducted by the Virginia Transportation Research Council, a partnership between VDOT and the University of Virginia, the optical speed bars are one of many methods being tested to determine whether safety practices used in other countries will work as well here. A British study has shown that optical speed bars reduced fatal and serious injury crashes; they already have been successfully tested in Texas, Kansas and Mississippi, transportation officials said.

Virginia recently received federal approval for the $2,000 Lee Chapel Road experiment from the U.S. Department of Transportation, which has also given the green light to a similar project along a stretch of Route 460 in the town of Zuni in southern Virginia, VDOT officials said.

"Our bottom line -- regardless of experimentation -- is safety for these motorists. In terms of the cost of this experiment, you're talking about peanuts compared to the costs of injuries and deaths," said Gene Arnold, a research scientist with the Charlottesville-based research council.

The posted speed limit on Lee Chapel Road is 40 mph. A recent VDOT study showed, however, that 85 percent of northbound motorists drive 15 mph over the limit and 85 percent of southbound motorists go about 7 mph over.

From 2002 to 2004, there were 22 crashes on the narrow stretch of road. Two, including one in August, were fatal. In 2002, the average annual crash rate along the section of Lee Chapel Road between Viewcrest and Pond Point drives was about 22 percent higher than the overall average rate for Fairfax County, according to VDOT.

Jeff Anderson, a longtime resident of the nearby South Run subdivision, said a fix for the speeding problem is long overdue. The car salesman remembered well a crash that killed a young driver last year.

"That was a real shame," said Anderson, 27. "It's a blind spot, and a lot of kids think it's cool to go fast over on that road."

The experiment might sound promising, but some traffic enforcement experts say there's no substitute for a marked patrol car with a radar gun and flashing lights to deter drivers from speeding.

"When I'm in an unmarked car, everybody is passing me," said Sgt. Terry Licklider, a Virginia State Police Department spokesman. "Yet, when I'm in a marked Chevy Impala, nobody wants to pass me. When people see a police car, they slow down."

Fairfax County police Capt. J.F. Bowman, the department's traffic unit commander, was less skeptical, saying yesterday that anything that slows drivers can't hurt.

"I've written tickets for people going 72 mph there. That's way too fast," Bowman said. "All it takes is for someone to pull out and not see you coming and you're going 72 mph and suddenly you've got a serious collision."

Results of the traffic experiment should be available in November or December.


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