Safety evaluation of converging chevron pavement markings
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Chevron pavement markings have seen rising interest in the United States as a means to reduce speeds at high-speed locations and improve safety performance. In Atlanta, there are two freeway-to-freeway ramps where chevron markings are being used. A previous study analyzed before-and-after speed data at these ramps and found only a modest reduction on overall vehicle speeds. However, a cursory crash analysis indicated that the ramps had crash reductions of over 60%, suggesting that safety benefits exist even though vehicle speeds are not significantly affected. This research aims to evaluate the safety performance of chevron markings on the two ramps in Atlanta, GA in order to quantify the potential impact of the treatment on safety and to understand the mechanism by which the treatment influences safety. This thesis begins with a literature review covering topics in human factors in safety, past uses of different types of pavement markings, and methods in using crash databases and police reports in accident studies. Next, the thesis presents an in-depth before and after analysis of crash data from crash databases and police reports provided by the Georgia Department of Transportation. And finally, the thesis concludes with a summary of findings and a discussion of further research needs. The results verified that there were 73% and 61% crash reductions in the two study ramps. Chevron markings appear to have benefitted all types of crashes and that they are possibly serving as a warning to drivers of potential upcoming hazards. Unavailability of a number of police reports and errors in crash databases were limitations to this study, and ultimately, new sites should be selected carefully and further studies need to be performed to better understand the treatment's benefits.