A Study on Reproducibility of Friction Data Collected Using a Continuous Friction Tester

Abstract

Japan is located between the latitudes of 20 and 45 degrees north, and its northern part is characterized by amounts of snowfall rarely seen at such latitudes in other parts of the world. In the 1990s, a ban was placed on the use of studded tires in Japan to prevent harmful environmental impacts from the dust they produced. However, as a result, the incidence of winter accidents on slippery roads has significantly increased, and measures to combat icy road surfaces have become a major part of winter road maintenance work. Salting and gritting are common practices, and where to apply these treatments is a key factor for refining them. In order to support prompt and accurate decision making, the authors have measured road surface friction using a continuous friction tester (CFT), which can perform constant measurement. In addition to the monitoring of road surface conditions (i.e., slipperiness) along routes, continuous friction measurement is also useful for identifying road sections and conditions that require special attention. However, variations in road surface conditions depend on a number of factors, such as weather, road surface temperatures, road structures, and topographical characteristics. Accordingly, there is a need to accumulate road surface friction data and related information for different weather conditions in order to support the establishment of diagnostic techniques for clarifying patterns of spatial variations in road surface friction and identifying where and when slippery conditions are likely to arise. In collaboration with road authorities, CFT data on road surface friction/temperatures and information on road structures were accumulated to clarify basic skidding characteristics and identify hazardous locations/conditions on the case study route. Reproducibility of road surface friction distribution was found under several weather conditions and certain friction tendencies at the tunnel entrance were also identified.