Versailles, France
Versailles, France
Time filter
Source Type

Betaille D.,IFSTTAR
2017 European Navigation Conference, ENC 2017 | Year: 2017

Positioning is one of the key functional components of intelligent transportation systems (ITS) with communication and computing. Road transport and Location Based Services will make use of GNSS for positioning purpose and both road and LBS are the main application domains of GNSS. This article focuses on urban applications. The rover is moving in streets where buildings around make urban trenches. The so called Urban Trench model is used to correct non-line-of-sight satellites. The principle is first presented. Then several modalities of applying this principle are addressed, in particular the a priori road lane map-matching of the rover position estimate. Last, experimental data are processed with this principle and its various applications, results are shown and analysed, so that first conclusions are drawn and research perspectives designed. © 2017 IEEE.

Touze-Foltz N.,IRSTEA | Farcas F.,Ifsttar
Geotextiles and Geomembranes | Year: 2017

This paper presents the results of uniaxial tensile tests, flow-rate measurements, and size-exclusion chromatography (SEC), which are used to evaluate the ageing of elastomeric bituminous geomembranes (BGMs) that were installed 6, 10, 15, 20, and 30 years ago in ponds at two different sites in France. SEC was used to detect oxidation and the absence of polymer in the bitumen at the surface of the 20- and 30-year-old BGMs. The results indicate that, for BGMs exposed less than 20 years, there was no oxidation or degradation of the polymer at the core. However, the elastomeric polymer was altered at the core of the 30-year-old BGM, resulting in an embrittlement of the bitumen, but this did not affect the mechanical properties of the glass veil and nonwoven polyester geotextile in the BGM core. Lastly, the flow rates through the BGM measured according to EN 14150 are still below 10-6 m3 m-2 d-1, which indicates that the elastomeric bituminous GM is still watertight after 30 years of exposure. © 2017 Elsevier Ltd.

International Journal of Applied Electromagnetics and Mechanics | Year: 2017

Deterministic Dynamic Programming is frequently used to solve the management problem of hybrid vehicles (choice of mode and power sharing between thermal and electric sources). However, it is time consuming and thus difficult to use in global sizing optimization or in parametric studies. This paper presents a comparison between three methods to compute the DDP problems. These methods are applied on the well known case of the Toyota PRIUS. It proves that a dense matrix method can reduce the computation time by up to 10 compared to more intuitive solving methods. © 2017 - IOS Press and the authors. All rights reserved.

Munduteguy C.,University Paris Est Creteil | Ragot-Court I.,IFSTTAR
Human Factors | Year: 2011

Objective: The aim of the study was to clarify how knowledge elaborated by specific experience may lead to erroneous expectations during interactions between drivers and riders.Background: Situation awareness is partly determined by prior knowledge. Unshared knowledge may cause difficulties in managing driving interactions, but there is still an important gap in the literature devoted to this field of research.Method: There were 226 participants, distinguished according to their vehicle use (for drivers, type of vehicle driven and whether they were exclusive or dual drivers; for motorcycle and scooter riders, the type of powered two-wheeler [PTW] used and its engine size) and their driving experience. Focusing on the most vulnerable users, we studied prior representations to interactions using a series of closed questions on drivers' performance relating to different stages of the interaction process from the perspective both of drivers' self-reflection and of riders' expectations.Results: Although most drivers are self-confident, their abilities tend to be questioned by riders. Owners of medium or large motorbikes feel that drivers do not assess their approach speed accurately. Similarly, scooter riders doubt drivers' ability to assess the distance that separates them from PTWs. Riders who use medium or large motorbikes are more likely to question drivers' skills in relation to crossing situations. Scooter riders do so more often for overtaking situations.Conclusion: The development of shared prior knowledge is essential to prevent accidents and incidents between drivers and riders.Application: To help improve effectiveness, we re-commend specific ways of embedding each type of road user profile in training, prevention, and research. © 2011 Human Factors and Ergonomics Society.

Orcesi A.D.,IFSTTAR | Frangopol D.M.,Lehigh University
Engineering Structures | Year: 2011

Management of bridges under uncertainty is an important issue for stakeholders. The use of probabilistic approaches enables one to consider uncertainties in the structural deterioration, assessment, and maintenance processes. Combined with optimization techniques, it is possible to determine management strategies that simultaneously minimize failure, assessment, maintenance, and rehabilitation costs. Nevertheless, there is a strong need in developing practical and efficient frameworks that enable stakeholders to optimize future allocation of budgets for facilities under uncertain structural parameters. In particular, providing an approach that is in agreement with stakeholders constraints still remains a challenge. Moreover, the use of structural health monitoring (SHM) in future management frameworks, to update structural performance, still needs further development. The objective of this paper is threefold: (a) provide management strategies in agreement with fixed budgets, (b) provide management strategies that consider the time delay between the assessment and the intervention schedule, and (c) include information provided by SHM in the decision process and analyze the impact of monitoring strategies on the structural analysis accuracy. An event tree based approach is proposed to consider various uncertainties in the decision process. Optimal solutions are associated with multiple criteria such as minimum expected failure cost, minimum expected inspection/SHM/maintenance costs, maximum agreement of expected inspection/SHM/maintenance costs to available budgets, and maximum accuracy of monitoring results. The approach is illustrated on an existing highway bridge. © 2011 Elsevier Ltd.

Granie M.-A.,IFSTTAR | Papafava E.,IFSTTAR
Transportation Research Part F: Traffic Psychology and Behaviour | Year: 2011

Gender differences in accidentology, notably on roads, are well documented and current research in social psychology tends to explain these differences by gender stereotypes, notably the association of risk-taking with social expectations concerning masculinity. To date, however, little research has explored gender stereotypes associated with vehicle driving. Beliefs about driving by men and women, as well as the effect of the age and gender of the perceiver, were explored using the free association method with 599 preadolescents and adolescents between 10 and 16 years of age. The results show that gender stereotypes are indeed associated with driving from the age of 10. While the representation of male drivers is already stable at this age, the representation of female drivers appears to develop with age. Furthermore, there is a notable in-group serving bias, but only among girls. The results are discussed in terms of an essentialist representation of genders, in-group/out-group relations, age differences in gender stereotypes associated with driving, and practical consequences on driver's training and socialization to risk-taking. © 2011 Elsevier Ltd. All rights reserved.

Accident Analysis and Prevention | Year: 2011

Male pedestrians are over-represented in road crashes. Among pedestrians, males violate more rules than females do. For now, it is not known whether gender differences in pedestrian behaviors only concern rule compliance. The objective of this study was to explore gender differences in pedestrian rule compliance and in gaze targets before and during crossing. 400 adult pedestrians were observed at two signalized and two unsignalized crossroads, using a taxonomic observation grid which detailed 13 behavioral categories before, during and after crossing. The results show that the temporal crossing compliance rate is lower among male pedestrians but spatial crossing compliance does not differ between genders. Furthermore, different gaze patterns emerge between genders before and during crossing, notably as women particularly focus on other pedestrians during these two periods whereas men focus on vehicles. Moreover, females' gazes vary with the type of crossroads, but males' gazes do not. Spatial crossing compliance and gaze targets are furthermore modulated by the crossroad configuration. These results are discussed in terms of pedestrian visual strategy and compliance. © 2011 Elsevier Ltd. All rights reserved.

Belaroussi R.,IFSTTAR | Milgram M.,University Pierre and Marie Curie
Expert Systems with Applications | Year: 2012

Face localization is the first stage in many vision based applications and in human-computer interaction. The problem is to define the face location of a person in a color image. The four boosted classifiers embbeded in OpenCV, based on Haar-like features, are compared in terms of speed and efficiency. Skin color distribution is estimated using a non parametric approach. To avoid drifting in color estimate, this model is not updated during the sequence but renewed whenever the face is detected again, that gives the ability to our system to cope with different lighting conditions in a more robust way. Skin color model is then used to localize the face represented by an ellipse: connected component segmentation and a statistical approach, namely the coupled Camshift of Bradsky, are compared in terms of efficiency and speed. The pursuit algorithms are tested on various video sequences, corresponding to various scenarios in terms of illumination, face pose, face size and background complexity (distractor effects). © 2011 Elsevier Ltd. All rights reserved.

Cord A.,IFSTTAR | Chambon S.,LUNAM University
Computer-Aided Civil and Infrastructure Engineering | Year: 2012

The state of roads is continuously degrading due to meteorological conditions, ground movements, and traffic, leading to the formation of defects, such as grabbing, holes, and cracks. In this article, a method to automatically distinguish images of road surfaces with defects from road surfaces without defects is presented. This method, based on supervised learning, is generic and may be applied to all type of defects present in those images. They typically present strong textural information with patterns that show fluctuations at small scales and some uniformity at larger scales. The textural information is described by applying a large set of linear and nonlinear filters. To select the most pertinent ones for the current application, a supervised learning based on AdaBoost is performed. The whole process is tested both on a textural recognition task based on the VisTex image database and on road images collected by a dedicated road imaging system. A comparison with a recent cracks detection algorithm from Oliveira and Correia demonstrates the proposed method's efficiency. © 2011 Computer-Aided Civil and Infrastructure Engineering.

Kane M.,IFSTTAR | Artamendi I.,Aggregate Industries UK Ltd. | Scarpas T.,Technical University of Delft
Wear | Year: 2013

This work focuses on the relation between the mineralogical composition of aggregates and their capacity to generate adequate friction between the road surface and the tyre after the polishing action of traffic. Three different types of aggregate namely greywacke, granite and limestone were used in the study. Petrographic examination of the aggregates was carried out using optical microscopy. The Wehner-Schulze apparatus was used to determine the evolution of friction with polishing cycles of both aggregates and asphalt specimens. A new aggregate hardness parameter was introduced based on the mineralogical composition and the hardness of the individual minerals. This hardness parameter was then related to friction coefficients measured on aggregate specimens after 180.000 polishing cycles. Initial results indicated that this new aggregate hardness parameter is a good indicator of the capacity of an aggregate to retain good friction levels. Changes in the microtexture of the aggregate during polishing were also analysed using a confocal microscopy technique. Microtexture measurements confirmed different levels of polishing for the different types of aggregates. © 2013 Elsevier B.V.

Loading IFSTTAR collaborators
Loading IFSTTAR collaborators