Ready to Rumble
October 1, 2011
Doctoral Student Researches Balance Between Highway Safety & Noise
The next time you are jarred from a lazy drift to the left speeding down a rural two-lane highway, Daniel Karkle should come to mind.
Karkle, a doctoral student at Kansas State University’s industrial and manufacturing systems engineering department, has been studying various aspects of the use and effectiveness of centerline rumble strips for the last four years with Malgorzata J. Rys, associate professor of industrial and manufacturing systems engineering.
His latest research findings, determining optimal installation distance of the strips for acceptable highway noise levels, appeared in the Journal of Transportation Engineering, a leading transportation journal.
Centerline rumble strips are raised or indented patterns installed on the center of undivided, two-lane rural highways. They are a countermeasure used primarily to prevent crossover crashes caused by drivers’ drowsiness or inattention. In 2009 there were nearly 2,600 fatal crossover crashes on rural highways in the United States.
Karkle’s article, “Centerline Rumble Strips: Study of External Noise,” examines the effects of speed, vehicle type, centerline rumble strip shape and distance on the levels of noise produced. These findings were then used to calculate the amount of noise created by the rumble strips, giving transportation agencies a guideline for installation distance to minimize effects on roadside residences and businesses. The study’s co-authors are Rys and Eugene Russell, K-State professor emeritus of civil engineering. It was funded in part through a grant from the Kansas Department of Transportation.
Karkle and his team found that the levels of noise were impacted by speed — the lower the speed, the lower the noise; vehicle type — heavier vehicles tend to produce more noise; and distance — the greater the distance, the lower the noise. They also found there was no significant difference in noise produced between football-shaped and rectangular centerline rumble strips.
Based on their research, a minimum estimated distance of 60 meters — or 200 feet — from the centerline is required to meet Federal Highway Administration standards for acceptable noise levels. At this distance the expected sound measurement would be in the range of 60 decibels adjusted — or dBA. This is comparable to the noise produced by a television set. The article is available at http://ascelibrary.org/teo/resource/1/jtpedi/v137/i5/p311_s1.
Earlier research shows that centerline rumble strips are effective in reducing crashes by approximately 25 percent in the United States. Karkle’s own research shows even greater benefits of from the use of centerline rumble strips in Kansas. In another study he has submitted for publication, more than 350 miles of Kansas two-lane, undivided rural highways with centerline rumble strips were analyzed. The results showed that following installation, correctable crashes were reduced by approximately 42 percent and those involving fatalities and injuries dropped approximately 46 percent. Specifically, crossover and run-off-the road crashes were reduced by some 68 percent and 35 percent respectively.
“There is clearly a trade-off between the safety impact of centerline rumble strips and the exterior noise created by them,” Karkle said. “This study shows there are important standard-of-living concerns to be considered when determining the appropriateness of installing centerline rumble strips on a particular stretch of highway.
“Interestingly, a limited qualitative study done in 2009 found roadside residents in Douglas County, Kan., believed that the increased safety effects were worth some level of noise,” Karkle said. “As the number of miles of highway with centerline rumble strips installed continues to grow more comprehensive, interviews should be conducted to determine acceptance or tolerance for the external noise.”
Karkle has two additional studies on centerline rumble strips under way. The first is a visibility study investigating the retroreflectivity of pavement markings installed over centerline rumble strips in both dry and wet conditions. According to Karkle, the primary aim of this research is determining how often these markings should be repainted, and secondarily if there are any differences in between the football-shaped and rectangular rumble strips.
The second study examines the effect of centerline rumble strips on vehicles’ lateral position and speed on rural roads with narrow shoulders.
“Because there are concerns that drivers will tend to overcorrect when they are alerted by the centerline rumble strip sound and vibration, it’s important to determine the minimum shoulder width necessary in order to safely install the rumble strips,” Karkle said.
Karkle was recently invited to participate in a colloquium for doctoral students and present his centerline rumble strip findings to date at the Institute of Industrial Engineers national conference in Reno, Nev. He hopes to publish results from his visibility and shoulder width studies prior to his graduation in December. While Karkle, who is from Brazil, is still uncertain about his postgraduation plans, he’s not ruling out working in the transportation field.
“Saving lives is a principal motivation behind my research,” he said. “I know the work I’m doing today will influence decision-makers and potentially prevent accidents for years to come.”