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June 2002
Researcher studies impacts of rumble strips
Kathleen Harder, a researcher working with the University's HumanFIRST Program, described her study of the effect of rumble strips on the stopping behavior of attentive drivers at rural intersections. Her presentation was part of the human performance and behavior track of the ITS Institute Research Showcase.
The purpose of her experiment, which was part of larger study funded by the Minnesota Local Road Research Board (LRRB), was to establish a baseline effect of in-lane rumble strips at rural controlled intersections. In laboratory testing, 32 subjects drove a simulated 25-mile course with 12 intersections, 9 of them controlled. The experiment tracked four independent variables—the number of strips (zero, two, or three), the type of strip (wheel track or full width), the presence of traffic, and the type of intersection (four way or two way). Strips were simulated with movement in the steering wheel and an auditory signal that resembled a strip sound.
Harder looked at three different points in the stopping process: first, the point at which the driver begins to slow down; second, the point at which the driver puts her or his foot on the brake; and third, the point at which the driver stops to the edge of the intersection.
The data showed "the variability of human behavior," Harder said. Results indicated that the presence of rumble strips had no effect on the first or third points. However, rumble strips did affect the second point—when the driver first taps the brake. "Without rumble strips, they put their foot on the brake far closer to the intersection than with two or three [strips]," Harder said. No difference was observed between using two or three strips, but wheel-track strips were found to be less effective than full-coverage strips.
This experiment was the first in a set of three to be conducted on in-lane rumble strips. In the second phase, starting this summer, the researchers will look at the behavior of sleep-deprived and alcohol-impaired drivers. The third phase—an investigation of the effectiveness of in-lane rumble strips on stopping behavior at problem intersections—will address traffic volumes, sight distance problems, and intersection layouts.