Portable Pendulum is the force developed when a tire that is prevented from rotating slides along the pavement surface (Highway Research Board, 1972). Skid resistance is an important pavement evaluation parameter because:

a) Inadequate skid resistance will lead to higher incidences of skid related accidents.
b) Most agencies have an obligation to provide users with a roadway that is "reasonably" safe.
c) Skid resistance measurements can be used to evaluate various types of materials and construction practices.