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The effect of contaminants has been overlooked and yet plays a significant role in driver safety and road maintenance. A laboratory test method is developed to reproduce the deposit of contaminant particles on the road surface and measure the friction coefficient on dry and wet-contaminated surfaces. It simulates in this way the variation of skid resistance of the road surface due to contaminants during a dry period-precipitation event and the washoff effect of the rain. Protocols are described with respect to the contaminant collection on site and the subsequent preparation in the laboratory, the spreading of contaminant particles on the road specimen and their compaction to simulate the effect of the traffic, the wetting of the test surface to simulate precipitations, and the friction measurement. Values of friction coefficient on clean and dirty dry surfaces as well as during the surface wetting (simulation of precipitations) are plotted. Comparison with the literature shows that the developed test method reproduces remarkably well qualitative graphs used to highlight the loss of skid resistance with time during a rain preceded by a long dry period. The effect of contaminant concentrations and traffic is shown. Explanations are given in terms of the masking of the road surface microtexture; they are supported by visual observation of the road surface before and after the contaminant deposit.

The paper deals with the modeling of friction between aircraft tires and contaminated runway surfaces. Wet-, snow- and ice-covered surfaces are considered. A tire Brush model developed for aircraft braking on dry runways is adapted to take into account the effect of contaminants. Compared with a dry surface, contaminants are assumed to affect the static and dynamic friction coefficients, the tire stiffness, the tire slip ratio and the length of the contact patch. Linear relationship is established between static and dynamic friction coefficients. The dynamic friction coefficient is reduced using an empirical model for wet surfaces and experimental fitting for snow- and ice-covered surfaces. The tire stiffness is modified considering the frequency and temperature dependence of the tire mechanical properties. Values on snow and ice are lower than those on wet and dry surfaces. A physical model is developed to calculate the length of the wet contact patch. Finally, it is assumed that the aircraft effective slip ratio is surface dependent; values are determined for each of the studied contaminants. Theoretical friction-slip curves are realistic in terms of shape and differentiation between surface conditions. The model is applied to a Falcon 20 aircraft and a runway monitoring device called IMAG. Friction-slip and friction-speed curves are calculated and compared to experimental data. It was found that the model can be used to relate ground friction to aircraft braking performance with enough reliability

Le rapport Étude sur les blessures, édition 2012 : Pleins feux sur la sécurité routière et dans les transports, le premier rapport de santé publique à l'échelle nationale en la matière, présente une synthèse des statistiques provenant de diverses sources sur les blessures survenues dans les réseaux routiers et de transport. Il établit le profil des blessures chez les Canadiens et les Canadiennes âgés de 24 ans et moins, explique les risques et les facteurs de protection et formule des recommandations sur les mesures à prendre. Les conclusions servent à guider l'élaboration de programmes ciblés de prévention des blessures.

The viscoelastic deformation of tire rubber by road surface asperities was modeled by the rolling contact between a Kelvin solid and a surface motif, which is the part of surface profiles between two peaks. Stress and strain calculations showed that contact losses might occur locally, depending on the rolling speed, the viscoelastic properties of the Kelvin solid and the geometry of the motif. Mean vertical and horizontal forces were calculated, from which a coefficient of friction was derived. The model was successfully coupled with a profile analysis method to predict tire/road friction at low speed from road surface microtexture. The contribution of various texture scales to friction was emphasized.

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