NCHRP Synthesis 14 (5) warned that any correlation between BPT and ASTM E274 would be “purely fortuitous” because the BPT not only measures friction at low speeds. But it also brings the edge of a rubber shoe (instead of a tire) into contact with the pavement NCHRP Report 37 (17) gave a correlation that was based on Dillard and Mahon, but cautioned that the correlation” is not very satisfactory,”