Effectiveness of experimental transverse-bar pavement marking as speed-reduction treatment on freeway curves

Abstract

Researchers performed a before-and-after analysis of speeds to determine the short- and long-term effectiveness of an experimental transverse-bar pavement marking treatment at the Plainfield curve on I-43-I-94 in Milwaukee, Wisconsin. The experimental transverse pavement marking treatment was installed in all lanes for each of the northbound and southbound directions of the curve In early September 2006. Each section of the pavement marking treatment was 1,000 ft long. The treatment sections consisted of a series of white transverse-bar markings installed with continuously decreasing spacing between successive markings, giving drivers the perception of increasing speed, potentially causing them to slow down. Each individual marking was 18 in. in lateral width by 12 in. longitudinally. Speed data were collected for 2 weeks in late July 2006; again in September 2006, approximately 1 week after the markings had been installed; and again in March 2007, approximately 6 months after the markings had been Installed (northbound only). The researchers used analysis of variance to analyze the mean speeds for more than 43,000 intervals of 5 min each measured at three locations in each lane of the northbound and the southbound directions. The results of the analysis suggest that the experimental transverse pavement marking treatment was effective at reducing curve speeds, especially shortly after installation. The marking treatment showed the greatest effects on speeds midway through the treatment section with approximately 1- to 4-mph reductions in mean speed observed between the before and the after periods. A lane-by-lane analysis showed that the marking treatment was most effective at reducing speeds in the shoulder and middle lanes, while speeds in the median lane were relatively unaffected.