A good skid resistance of the pavement surface is of essence for road safety. Loss of skid resistance can have dramatic material and loss of life consequences. The problem is aggravated further in the presence of water, due to the phenomenon of hydroplaning. In the FP7 SKIDSAFE project the micro-mechanical factors controlling skid resistance at the tyre-pavement interface in asphalt concrete pavements shall be identified and related to asphalt mix characteristics on the basis of experimental evidence and computational studies.

In the first phase of SKIDSAFE, the microtextural, geometrical and mineralogical properties of typical European aggregates shall be measured experimentally. For the measurement of the contact frictional characteristics of various aggregate to rubber interfaces, a new interface testing device shall be developed. The data collected will be used to develop friction constitutive models for aggregate-rubber friction. Asphalt mix surface texture measurements will be done to create a realistic finite element (FEM) mesh. This will be used together with the friction constitutive models and a contact algorithm for 3D FEM simulations of asphalt mix surface - rubber interaction under dry/wet conditions. In the simulations both, the surface and the bulk characteristics of the asphaltic materials shall be accounted for. The results will be verified by means of interface tests between asphalt concrete and rubber. Parametric FEM simulations should lead to the identification of relations between mix design and friction characteristics The interrelation between asphalt mix design and the in time development of pavement surface skid resistance under various pavement surface moisture conditions shall be investigated by extensive field measurements on several European pavements. These shall be supplemented by dynamic nonlinear finite element simulations of the interaction between a rolling tyre and the underlying pavement structure. The finite element analyses shall enable the identification and the quantification of the contribution of the various processes and mechanisms to the in time development of skid resistance recorded by the field measurements.

In the second phase of SKIDSAFE, focus shall be placed on the extreme case of skidding due to hydroplaning under wet conditions. An instrumented vehicle equipped to measure hydroplaning related quantities (like water film thickness and tire to road forces and moments) will be used to collect data necessary for calibration of a FEM model that for simulation of hydroplaning on the basis of a newly developed hydrodynamic algorithm. Parametric FE runs will enable the development of relations between mix design and sensitivity to hydroplaning. The formalistic relations for skid resistance that will be developed will be based on the performed laboratory and field tests as well as on the results of the finite element parametric analyses.
Pavement management tools shall be developed for mix design, variable speed limits and optimal pavement maintenance strategies.

Because of time and resource limitations it will not be possible in the framework of this project to perform tests and/or analyses to cover all possible combinations of parameters that may be encountered in practice. For this reason, protocols shall also be developed to enable the potential user to perform tests, process the results and determine the necessary input parameters for materials outside the range of the SKIDSAFE materials.