Many roadway factors have an effect on driver behavior. Geometric, roadside, and traffic control device variables that may affect driver behavior on four-lane suburban arterials were investigated. Traffic signals and traffic volume were considered within the study site selection and data collection criteria and, therefore, were not included in the analysis. Regression techniques were used to determine how selected variables affect operating speed on horizontal curves and straight sections. When all variables were considered, posted speed limit was the most significant variable for both curves and straight sections. Other significant variables for curve sections were deflection angle and access density class. In another series of analyses performed without using posted speed limit, only lane width was a significant variable for straight sections, but median presence and roadside development were significant for curve sections. The analysis that included posted speed limit, however, produced stronger relationships between speed and significant variables than did the analysis that excluded posted speed limit.
Background and current status of the development of updated minimum in-service retroreflectivity levels for traffic signs in the United States are described. A summary of the earlier work, conducted from the late 1980s to the mid-1990s, is provided along with descriptions of the relevant validation work. Related events that occurred in the late 1990s are described, and it is shown how, when combined with the assumptions and limitations of the earlier minimum retroreflectivity research, they resulted in a need for updated minimum retroreflectivity levels. The research related to the updated minimum retroreflectivity levels is summarized. A brief description of a second round of national minimum retroreflectivity workshops is also provided. The most recent set of recommended minimum retroreflectivity levels for traffic signs is presented along with a list of suggested research topics based on the limitations associated with the recommendations.
This research was initiated to determine whether a correlation between pavement marking retroreflectivity and safety could be established. Previous research on this topic provided mixed results and sometimes counterintuitive findings. Using data from Michigan, the researchers evaluated relationships between crashes and longitudinal pavement marking retroreflectivity. The retroreflectivity data consisted of pavement marking measurements representing white edge lines, white lane lines, yellow edge lines, and yellow centerlines. The data included crashes and retroreflectivity measurements from 2002 to 2008. Only nighttime crashes that occurred at nonintersection and noninterchange segments during the nonwinter months (between April and October) were considered (wet crashes were also excluded). The following specific types of crashes were initially identified as target crashes for this study: nighttime, single vehicle nighttime, fatal plus injury nighttime, and single vehicle nighttime fatal plus injury. The findings lend support to the positive safety effects of maintaining retroreflectivity of pavement markings.
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