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July 11, 2006


Can an Optical Illusion Slow Speeders?
VDOT Testing Section of Route 460 in Zuni
ZUNI – If pushing the speed limit is your thing, you may start getting an unusual inkling that you need to slow down. Not a chance? Well, new pavement markings being tested by the Virginia Department of Transportation (VDOT) have been proven to make some motorists think they’re going faster than they really are – and in turn, drivers have let up off the accelerator.
VDOT and its research division, the Virginia Transportation Research Council, hope to learn whether optical illusions can slow speeders on a section of U.S. 460 in Zuni. Beginning the week of July 10, VDOT will install “optical speed bars” – a series of lines placed at decreasing intervals on the roadway – that visually give drivers the perception they are moving faster than they intended. The pattern of lines is also meant to get drivers’ attention so they will slow down.

“Route 460 is one of the most heavily traveled corridors in the region,” said Mike Corwin, VDOT traffic engineer in Hampton Roads. “We are optimistic that this study will add to our proactive efforts to get drivers to slow down through local communities.”

The optical speed bars pilot study is a part of a larger project the Virginia Transportation Research Council is conducting for VDOT to determine whether certain safety practices used successfully in other countries will work as well in the United States and Virginia.
A British study of optical speed bars found they reduced fatal and serious injury accidents and maintained their effectiveness for four years after the initial data were collected. In the United States, optical speed bars are being tested in Texas, Kansas and Mississippi. Two areas are being tested in Virginia, including Route 460 in Zuni and Lee Chapel Road in Fairfax County.
This one-mile segment on U.S. 460 is a four-lane, undivided highway that runs through the Town of Zuni. This particular section has a curve where Route 644 intersects with Route 460, limiting sight distance along the roadway in that area.
The speed limit on U.S. 460 on the approaches to Zuni is 55 mph, with a 45 mph limit through town. To improve the safety of this stretch, VDOT’s Hampton Roads District installed speed reduction signs approximately 600-feet in advance of the 45 mph speed limit signs on both sides of the town. There are also curve warning signs on both approaches. Additionally, signs advise motorists to watch for turning traffic in the vicinity of the intersection with Route 644.

Despite these efforts, motorists still tend to speed through the area. VDOT hopes to learn more about drivers’ tendencies as a result of installing the optical speed bars. Plans include conducting a basic before and after study to compare volumes, speeds, and classifications obtained from traffic counters.

The Virginia Transportation Research Council is a partnership of VDOT and the University of Virginia and is located on the U.Va. Grounds in Charlottesville. More information about VTRC is available at