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Using optical illusion to slow down drivers
Make law abiding motorists believe they are driving even faster than they are and they will quickly slow down. That at least is part of the theory behind Japan's system of converging "chevron" road markings that produce the optical illusion of speed. The Japanese have used them to slow traffic on bridges and the chevrons seem to be effective in slowing vehicles when they leave freeways.
Now a US research team working with the Wisconsin Department of Transportation has trialed the patterns on an American highway and come to the conclusion that the design concept should be given qualified endorsement.
Although the researchers from Marquette University have offered only qualified approval, the problem is not because they noticed any failures. It was simply a series of "mishaps" that plagued the test program. (For example, research observations did not begin until nearly two years after the markings were painted on the road.)
Nonetheless, despite the fact that regular road users had more than enough time to get used to the optical illusion before measurements began, the drivers still responded to the chevrons by applying their brakes. The illusion of speed is created by painting the chevrons on the road surface at increasingly close intervals. When the motorist drives over them, he or she gets the impression of driving faster than they really are.
The Wisconsin chevrons were painted on a slip road leading from a major highway. It was assumed that drivers would be entering the slip road at 65 mph (about 105 km/h) and would be required to reduce speed quickly to 50 mph (about 80 km/h).
Speed signs were up and 16 sets of chevrons extended for about 190 metres along the slip road. A similar slip road without chevrons was used as a comparison.
The researchers found the chevrons use "appeared to result in a large speed reduction" and they quoted raw data suggesting a significant reduction in crashes too. But because of the problems encountered conducting the tests, they say more research is still needed before any final endorsement.
