Citation

Zimmerman K, Larson R. Transp. Res. Circular 2005; (E-C078): 159-172.

Copyright

(Copyright © 2005, U.S. National Academy of Sciences Transportation Research Board)

DOI

unavailable

PMID

unavailable

Abstract

One of the benefits associated with the use of a pavement preservation program is improved safety characteristics. Improved safety can be realized in several ways. For instance, an agency with a pavement preservation program that includes the early application of preventive maintenance (PM) treatments can generally keep the road network in better condition for a longer period of time. As a result, the roads are relatively smooth, which reduces the cost of operating a vehicle and minimizes crashes associated with defensive driving to avoid potholes and other surface irregularities in the pavement. However, in addition to providing a smoother surface, PM treatments can be used to improve the surface characteristics associated with surface texture (friction) to reduce the likelihood of wet weather and dry weather crashes. In the United States and abroad, an increased emphasis is being placed on safety issues to reduce the number of fatal and serious injuries caused by crashes and the resulting traffic delays. However, the effect of microtexture and macrotexture on crash rates has not been quantified. Past studies have often shown a weak link between increased friction and reduced crash rates. Recently, there have been major advances in data collection and analysis capabilities that show promise for improving the ability of transportation agencies to better quantify the effectiveness of pavement preservation treatments on reducing crash rates by improving surface characteristics. For instance, it is now possible to collect continuous pavement macrotexture information at highway speeds. It is also possible to measure macrotexture under the tire during skid trailer friction testing. These technological advances will greatly enhance the ability of highway agencies to identify sites of potentially high accident rates and to proactively take preventive actions as part of a pavement preservation program. This paper focuses on the safety improvements that can be realized as part of a pavement preservation program. Specifically, the following areas are discussed in this paper: (1) the use of network-level evaluations (including features such as pavement macrotexture and annual friction surveys) as a means of identifying pavement sections that could benefit from the use of certain PM treatments to enhance or restore friction values (such a microsurfacing, grinding and/or grooving, or chip seals); (2) the development of safety investigatory levels based on microtexture and macrotexture data for various site categories; and (3) the incorporation of safety features into a pavement management analysis. The application of these characteristics are demonstrated using examples from transportation agencies worldwide. For instance, the Texas Department of Transportation’s Wet Weather Accident Analysis Program is an example of the type of study used to illustrate the points raised. Internationally, work being conducted in the United Kingdom and New Zealand on continuous friction measurements and the use of the data to identify pavement sections where poor texture/friction may be contributing to higher than average crash rates are featured. Other examples, such as Australia’s recently established goal of achieving 19% of their 40% per capita accident reduction by providing safer roads is also documented.