Safety of wider edge lines in The USA

One of the most important aspects of a safe and efficient roadway is the uniform application of pavement markings to delineate the roadway path and specific traffic travel lanes. Pavement markings can communicate information to road users like no other traffic control device because they provide continuous information to road users related to the roadway alignment, vehicle positioning, and other important driving-related tasks. In the United States, almost $1 billion was spent on pavement markings on State maintained roads in 2007. When local and private roads and parking areas are included, it is estimated that approximately $2 billion was spent on pavement markings in 2007 (Carlson 2009). Despite the national expenditures on pavement markings, a highway death occurs as a result of a lane departure every 21 minutes, according to a recent American Association of State Highway and Transportation Officials (AASHTO) report (AASHTO 2009). Prevention of roadway departure crashes is one of the Federal Highway Administration's (FHWA) four focus areas for safety. In addition, AASHTO has developed its Strategic Highway Safety Plan that is designed to reduce these crashes (AASHTO 2008). The first objectives of the FHWA focus areas and AASHTO Safety Plan are to keep vehicles in their lanes and on the roadway. Installing and maintaining effective pavement markings is one immediate and obvious way to meet these objectives. An on-going research study in the United States is focused on pavement markings and includes several topics: study the safety impacts, environmental impacts, and cost effectiveness of different pavement marking systems and the effect of State bidding and procurement processes on the quality of pavement marking material employed in highway projects. The research includes an evaluation of the impacts and effectiveness of increasing the width of pavement marking edge lines from the traditionally used width of 4 inches. This paper presents preliminary findings from robust statistical analyses which provide strong quantitative support for the elusive link between pavement marking width and safety. The researchers used an Empirical Bayes (EB) before-after statistical analysis and an independent cross-section analysis. The findings show that the installation of wider edge lines results in reductions in several relevant crashes. These retrospective analyses, which incorporate several years of actual crash data, are considered more powerful than observational studies with a limited number of observations of driver performance.