TTD dynamic surface properties of initial vertical impact in the laboratory and in situ (racetrack).

Racetrack averages (average over all other factors) of the dirt (MeanD) and synthetic (MeanS) surfaces, and their difference (ΔSurfT = MeanD−MeanS), were used to assess the magnitude of ΔL,T (average of laboratory value minus racetrack average for each property). If PT| = absolute value of the difference between dirt and synthetic racetrack averages (ΔSurfT).