Skid resistance of asphalt pavements : laboratory measurements and model assessment

Abstract

For a car to be able to brake, accelerate or change direction, it needs a sufficient level of friction between its tyres and the pavement surface. The tyres play an important role, but road authorities are only responsible for an adequate level of skid resistance of the pavement surface. The skid resistance of a pavement changes over time due to various processes, such as polishing, wear and weathering, but also temporary effects such as temperature or dust accumulation. Road authorities perform skid resistance measurements on a regular basis in order to be able to plan and perform timely maintenance to restore skid resistance. There are only in Europe 14 skid resistance measurement devices with different working principles and different technical characteristics, such as the type of tyre, the measurement speed, the type and amount of wheel slip, the vertical load, etc. These differences make that the measurements are comparable, but there is no unique correlation, since the response to changes in the friction conditions are different for each measurement device, and especially for each type of rubber used for the testing wheels.

Semi-empirical method for the calculation of shear stress, stiffness and maximum shear strength of bituminous interfaces under in-service conditions

“…In addition to the indicated vertical load (V=49 kN), a longitudinal horizontal load Hx=0.55V has been considered that has been assumed representative of the tangential force exerted by a braking and partially locked wheel. This locking is described as partial because, under certain conditions and on a dry pavement, the friction coefficient (µ) tyre-pavement can reach values between 0.80 and 0.90 [30,31,32]. The loading times that will be adopted to obtain the displacement speed between the boundaries of the interface correspond to a vehicle speed and, consequently, a load speed of 60 km/h.…”