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5 1. Chapter 1 Introduction According to the Fatality Analysis Reporting System (FARS), in 2004 there were 38,253 fatal crashes resulting in 42, 636 fatalities (4). By comparison, the attack on Pearl Harbor killed 2,403 Americans (5), while the September 11, 2001 attacks killed 2,986 people (6). Both attacks united the nation for a commitment to victory in response. While not as commanding of national attention, traffic crashes kill more people than all the fatalities from wars put together. Therefore, any safety measure which increases visibility and potentially assists drivers in staying within their lanes deserves serious consideration. Longitudinal pavement markings and to a lesser extent pavement markers are ubiquitous on highways and freeways in the United States. Pavement markings and markers provide drivers with information about their position within their own lane, and provide previews of upcoming changes in the roadway geometry, including curves, lane drops, narrowing, and the start and end of passing zones. Visibility of pavement markings and markers are particularly important during dark or unlighted conditions. The visibility of pavement markings and markers at night is related to their retroreflectivity, defined as reflected brightness, where the reflected light source is usually automobile headlights and is expressed in units of millicandellas per meter squared per lux (mcd/m2/lux). The performance of pavement markings and markers is a function of the materials used such as waterborne paint, thermoplastic, and epoxy (while markers may be designed as plowable or non- plowable), color (white or yellow), traffic volume, pavement surface type (asphalt or concrete), and climate. However the most important factor is the age of the pavement markings and markers since over time the materials used are worn off of the pavement. As pavement markings are worn off and markers separated from the pavement over time, their visibility naturally degrades. This study focuses upon how non-intersection, non-daylight (night, dawn, and dusk) safety is impacted by the change in retroreflectivity of longitudinal pavement markings and markers. In order to estimate retroreflectivity, models were developed as a function of key performance variables and applied retroactively to locations of known pavement marking and maker installation dates and materials. The estimated retroreflectivity was then compared to the number of non-intersection, non-daylight crashes occurring over time on multilane freeways, multilane highways, and 2-lane highways using an innovative analysis methodology developed for this study.
6 The body of this report has been structured into six chapters: the findings of the review of the related pavement marking and marker literature (Chapter 2), the description of the innovative methodology developed for this study (Chapter 3), the data collection and preparation (Chapter 4), the modeling of retroreflectivity and safety analysis (Chapter 5), the discussion of the study results (Chapter 6), and the final conclusions and recommendations (Chapter 7).
