Indirect Skid Resistance Measurement for Porous Asphalt Pavement Management

This paper focuses on developing a method for road managers to assess the sideways-force coefficient (SFC) in porous asphalt with low-cost standard tests. SFC can be used as a component in road surface condition surveys and asset management decisions. A standard piece of equipment for determining SFC is the sideways-force coefficient routine investigation machine (SCRIM), which can be truck or trailer mounted. This equipment is often beyond the budget of most small, low-volume road agencies. An empirical model for the indirect estimation of SFC for porous road surfaces was developed as a result of this study. With hand-held equipment the portable skid resistance tester [to derive the British pendulum number (BPN)] and the sand patch method [height in sand (HS) test] a correlation of these test results can be made, and a reasonable approximation to SFC with the use of the SCRIM method can be attained. BPN, the unit of measurement of the skid tester, is a representation of the microroughness of the wearing surface, and the sand patch method (HS test) results yield the macroroughness of the pavement. The study was conducted over 20-km segments of low-volume roadway in southern Italy. The initial results are promising, with a maximum percentage of error of less than 15.2%. Further study is needed to adapt the model to other road surface conditions.