Evaluation of International Friction Index and High-Friction Surfaces

Abstract

State highway agencies have an obligation to provide users with optimal surface conditions under various weather conditions throughout the year. A satisfactory pavement surface should exhibit good friction and texture depth to reduce roadway highway accidents. This is why friction is starting to receive increased attention in the pavement management process.

There have been numerous research efforts by different countries and agencies to better understand the behavior of different friction testing devices and the influence of texture, speed, and other external conditions on their measurements.

The first part of this thesis presents a research effort to compare and harmonize texture and skid resistance measurements taken with various devices on 24 pavement sections with a wide range of textures. Measurements were compared and the International Friction Index (IFI) calculated following PIARC and ASTM steps.

The results revealed discrepancies in the IFI values calculated for the different devices, suggesting that the coefficients A, B, and C proposed by PIARC may need to be adjusted for each device considered before the IFI can be implemented by the surface properties consortium participating agencies. In this research the A, B, and C coefficients were then recalculated, and the predicted values of friction using these revised coefficients are presented. The coefficients developed were also used to obtain IFI values for high-friction surfaces (HFS).

It has been found that under different conditions, different parameters and coefficients will result. It is strongly recommended equipment comparison experiments (like the NASA and Smart Road programs) continue to better determine the coefficients necessary for harmonization.

HFS have emerged as viable high-friction pavement alternatives that mitigate the consequences of driver error, poor geometric alignment of the roadway, and insufficient friction at the tire-pavement interaction, especially during wet weather. This thesis presents a study of the HFS available in the U.S. market and their performance (friction and texture) in different applications, under different weather conditions, and in various locations. This thesis also presents the results of the benefit-cost analysis for the studied HFS.