Véronique Cerezo

Hydroplaning speed and infrastructure characteristics

Abstract This article exposes some results of a study, which aims at modelling the hydroplaning phenomenon taking into account the infrastructural characteristics, the water-depth on the road, the load transfer between the rear and the front wheels, and the skid resistance before total hydroplaning. First, a short bibliographical study determined the most relevant parameters that should be included in a global hydroplaning model such as the tyres’ characteristics (pressure, contact area, and tread depth), the load, the water-depth, the road profile, and macrotexture. Among them, the water-depth is the most difficult to evaluate, because it deeply depends on the pavement irregularities (roughness and texture), the road geometry, and the weather (rainfall intensity). Thus, a model calculating the water-film thickness by using road characteristics measurements is proposed. This initial water-depth is included in a linear model with 2 degrees of freedom, which describes the longitudinal dynamics phenomenon. The load transfer between the front and the rear axles is calculated in a straight line. Moreover, the water-depth in front of the rear tyre is calculated by considering the water displacement generated by the front tyres. Then, the increase of the water thickness just in front of the tyre due to the flow in the tyre treads and the pavement macrotexture is modelled. Finally, this model provides a hydroplaning speed, which is used for warning the drivers.

Road surface texture and skid resistance

This paper deals with the relationship between road surface texture and skid resistance. Mechanisms underlying the tire/wet road friction are first described. Definitions of road surface irregularities scales are given. The rest of the paper is then focused on the macrotexture and microtexture scales and their respective roles in what happens at the tire/road interface. Existing methods to measure and characterize the road surface texture are presented. On the one hand, problems encountered when using sensors developed for machined surfaces for the measurement of road surface profiles or cartographies are discussed. On the other hand, potential improvements when applying characterization methods developed for machined surfaces to road surfaces are highlighted. The paper presents finally modeling approaches to calculate friction forces from road surface texture. The generalized form of the models is presented from which terms related respectively to the macrotexture and the microtexture are identified. Approaches used to calculate these terms, integrating eventually other variables, are presented.

Laboratory test to evaluate the effect of contaminants on road skid resistance

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.

Friction/water depth relationship—In situ observations and its integration in tire/road friction models

The purpose of this paper is to provide new experimental evidences about the friction/water depth relationship and to improve the formulation of friction models in terms of consideration of the effect of water depth. Tests are conducted on test tracks. Friction forces are measured by means of a dedicated trailer providing a locked-wheel (full sliding) friction coefficient. The test surfaces are wetted by an on-board wetting system providing water depths varying from 0.1 mm to 1.50 mm. Effect of the road surface texture on the friction/water depth variation is shown and commented. Inputs newly provided by field tests, compared with laboratory tests, are highlighted. The obtained friction/water depths curves are assimilated to Stribeck curves and analyses, assuming conditions of a starved lubricated contact, are conducted to determine the lubrication regimes experienced by the tire/road contact when the road surface changes from dry to wet. A new friction model is formulated using the three-zone description of the tire/road contact area. The formulation is focused on the water drainage term reflected by a so-called hydrodynamic term FHL. It was assumed that FHL is a product of elementary functions expressing the respective effects of water depth, speed, tire tread depth, and road surface macrotexture on water drainage. Form of the elementary functions is derived from experimental evidences and consideration of previous friction models. Fitting of the new model to experimental data is shown and comparison with previous models is discussed.

Contribution to pavement friction modelling: an introduction of the wetting effect

ABSTRACT This paper presents a friction model describing the tyre rubber/road interaction that takes into account the viscoelasticity of the tyre rubber, the texture of the road surface and a water layer between the tyre/road interface by introducing explicitly a computation of the water layer effect in the calculation process of the hysteretic friction. The geometry of the wetted portion of the interface model is simplified by transforming it into an equivalent hydrodynamic bearing. Utilising the Reynolds equation, the bearing load capacity is calculated and the resulting forces are subtracted from the contact load when calculating the forces of the hysteretic friction. The mechanical behaviour of the rubber is represented in the model by Kelvin–Voigt model. The frictional forces due to hysteresis are calculated at any given operating conditions (load, slip speed, etc.) from the contact geometry of rough surfaces caused by the viscoelastic behaviour of rubber. To validate the model, a set of surfaces including real pavements and artificially textured slabs were selected covering a wide range of microtexture and macrotexture combinations and the computed and measured friction compared. To describe the contact geometry of rough surfaces using macrotexture and to measure actual friction, the Circular Track Meter and the Dynamic Friction Tester devices were used, respectively. The friction coefficients computed using the model were compared to the measured friction coefficients. The obtained results are presented in the paper and proved to provide high correlation between the measured and modelled friction. The model is capable to predict wet friction at low as well as high speeds on wet surfaces, thus proving to be capable to take adequately the wetting effect on the variation of friction with increasing speed. Recommendations are provided to improve the model and extend it to a tyre friction model.

A multi-objective optimisation approach for sustainable pavement management

Abstract Addressing the multidimensional challenges involved in advancing the sustainability of pavement systems requires the development of optimisation-based decision support system (DSS) for pavement management with the capability to identify optimally sustainable pavement maintenance and rehabilitations (M&R) strategies. The main objective of this research work is to develop a multi-objective optimisation framework that hosts a comprehensive and integrated pavement life cycle costs–life cycle assessment model that covers the pavement’s whole life cycle, from the extraction and production of materials to construction and maintenance, transportation of materials, work-zone traffic management, usage and end-of-life. The capability of the proposed DSS is analysed in a case study aiming at investigating, from a full life cycle perspective, the extent to which a number of pavement engineering solutions are efficient in improving the environmental and economic aspects of pavement sustainability, when applied in the management of a road pavement section. Multiple bi-objective optimisation analyses considering accordingly agency costs, user costs and greenhouse gas emissions were conducted based on a multi-objective genetic algorithm. Pareto fronts were obtained for each analysis, originating a set of non-dominated maintenance and rehabilitation solutions. Posteriorly, a multi-criteria decision analysis method was used to find the best compromise solution for pavement management.

Optical Microtopographic Inspection of Asphalt Pavement Surfaces

Microtopographic and rugometric characterization of surfaces is routinely and effectively performed non-invasively by a number of different optical methods. Rough surfaces are also inspected using optical profilometers and microtopographer. The characterization of road asphalt pavement surfaces produced in different ways and compositions is fundamental for economical and safety reasons. Having complex structures, including topographically with different ranges of form error and roughness, the inspection of asphalt pavement surfaces is difficult to perform non-invasively. In this communication we will report on the optical non-contact rugometric characterization of the surface of different types of road pavements performed at the Microtopography Laboratory of the Physics Department of the University of Minho.

Effect of NBR-Waste on Rheological Properties of Modified Bitumen and Mechanical Characteristics of the Asphalt Mix

Under the effect of severe climatic conditions and heavy vehicles traffic, premature and irreversible damages occur on road pavements carried out with conventional bituminous materials.

Risk assessment in ramps for heavy vehicles—A French study

This paper presents the results of a study dealing with the risk for heavy vehicles in ramps. Two approaches are used. On one hand, statistics are applied on several accidents databases to detect if ramps are more risky for heavy vehicles and to define a critical value for longitudinal slope. χ(2) test confirmed the risk in ramps and statistical analysis proved that a longitudinal slope superior to 3.2% represents a higher risk for heavy vehicles. On another hand, numerical simulations allow defining the speed profile in ramps for two types of heavy vehicles (tractor semi-trailer and 2-axles rigid body) and different loads. The simulations showed that heavy vehicles must drive more than 1000 m on ramps to reach their minimum speed. Moreover, when the slope is superior to 3.2%, tractor semi-trailer presents a strong decrease of their speed until 50 km/h. This situation represents a high risk of collision with other road users which drive at 80-90 km/h. Thus, both methods led to the determination of a risky configuration for heavy vehicles: ramps with a length superior to 1000 m and a slope superior to 3.2%. An application of this research work concerns design methods and guidelines. Indeed, this study provides threshold values than can be used by engineers to make mandatory specific planning like a lane for slow vehicles.