Good skid resistance of the pavement surface is essential to road safety. Loss of skid resistance can result in accidents and loss of life. The presence of water, due to the phenomenon of hydroplaning, reduces skid resistance. In this 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.
SKIDSAFE attempts to examine the processes taking place at the interface between the pavement surface and the tire. The project aims at integrating state-of-the-art tire models with rolling contact algorithms, hydrodynamic algorithms for simulation of the effects of water and advanced constitutive models.
These models will then be used to simulate the physical processes contributing to friction and wear in the interfacial zone between the pavement surface and the tire. The processes happening in the bulk body of the pavement structure as a result of friction will be also investigated. Furthermore, the parameters necessary for calibration of all components shall be obtained by extensive experimental studies.
The overall objective is the development of a micro-mechanical, multi-physics computational tool for the prediction of the progressive loss of skid resistance as a function of the composition of the pavement surface and the deterioration of its characteristics with traffic loading.
In the first phase of the project, the skid resistance characteristics of various combinations of dry pavement surfaces and tyre types shall be evaluated experimentally. The tests shall provide the information necessary for micro-mechanical finite element simulations of tyre-pavement interaction.
A state of the art 3D rolling contact algorithm, accurate representation of the tyre characteristics and the surface morphology shall be utilised. On the basis of the simulations, the parameters controlling the magnitude and the degradation of skid resistance in dry pavements shall be identified. These parameters shall be used as input for wet pavement analyses in the second phase of the project in which focus shall be placed on the detrimental influence of water on skid resistance. The rolling contact algorithm shall be extended by a hydrodynamic component to enable simulation of hydroplaning.
On the basis of these simulations, the influence of water on the parameters controlling the magnitude and the degradation of skid resistance in wet pavements shall be identified. In particular, the influence of progressive pavement surface unevenness shall be investigated. Design tools will be produced for the evaluation of the critical asphalt mix parameters on the dry and wet skid resistance degradation as a function of tire type and driving speed. These can be used by road authorities to decide for the choice of safe driving speed limits.
Reducing skid-related accidents
Road slipperiness contributes to car accidents and fatalities. An EU initiative set out to design novel tools and techniques to measure and ultimately prevent the loss of skid resistance.
Water can have a major effect on road surface friction, and its impact on the traction produced by tyres can result in dangerous driving conditions. Existing methods and devices that measure the skid resistance of road surfaces are limited in scope and do not account for the different elements that influence tyre and road friction.
The EU-funded 'Enhanced driver safety due to improved skid resistance' (http://www.skidsafe.org (SKIDSAFE)) project looked at how the pavement and the tyre interact. This helped to create tools that predict the cumulative loss of skid resistance in relation to the wear of the pavement.
To explore the interaction between the pavement and the tyre, the project team designed and manufactured a device that carries out tests on different dry pavement surfaces and tyres. Advanced tyre models and algorithms were used to reproduce scenarios that help cause friction and wear between the surface and the tyre.
The simulations led to the identification of factors that influence the extent and the deterioration of skid resistance on dry pavements. These factors were then used to examine the negative impacts of wet pavements. A test vehicle was used to demonstrate skidding due to wet road surfaces.
Based on the findings, three pavement skid-resistance management tools were developed.
By introducing innovative pavement management solutions to measure the skid resistance of road surfaces, SKIDSAFE should reduce traffic accidents while helping authorities to determine safe speed limits.