Human slip assessment of candidate reference surfaces for walkway tribometer validation: An update to standard ASTM F2508, 2022Blanchette, Lee-Confer, et al. (ASTM). Previous studies have reported on the concept of using human subjects to rank and differentiate walkway surfaces that vary in slipperiness. Surfaces identified as having different levels of slipperiness, based on the outcomes of human subject walking trials, are then used to validate tribometer slip resistance measurements. This concept was adopted in the development of ASTM F2508-11, Standard Practice for Validation and Calibration of Walkway Tribometers Using Reference Surfaces. Because of a depleting supply of the reference surfaces cited by ASTM F2508, new reference surfaces are needed. In this study, the authors' objective was to assess new candidate reference surfaces to update the ASTM F2508-16, Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces. One hundred and forty-eight human subjects walked across four ceramic-based tiles (E, F, G, and H) under contaminated conditions. The results revealed that, consistent with the authors' prior studies, human subjects were able to rank and differentiate surfaces according to slipperiness. Moreover, the surfaces evaluated in this study demonstrate characteristics that make them suitable replacements for the ASTM F2508 reference surfaces. Based on these findings, the authors recommend that ASTM F2508 be updated using surfaces E, F, and G and that surface G be considered a candidate to establish a slip resistance threshold for walking.