Analyse des pratiques d'accompagnement des enfants et de leurs conséquences

It is more and more common to escort children, and adolescents in rural areas, to school, to see friends, to leisure activities, to the doctor's etc. Some elderly persons are also systematically escorted to activities. These escorting trips are mainly by car, with the mother (or the daughter) driving. Whether children are escorted or not varies according to their age, but the practice has becoming increasingly prevalent in Europe since the 1970s. In England children are allowed to travel unescorted average two and a half years later in 1990 than was the case in 1970 and in the same period the percentage of trips which are escorted has increased by a factor of three and a half. Road safety problems and general insecurity in the area where they live lead parents to escort their children. Most trips of this type are by car. The same situation applies in the former East Germany where many households have only recently acquired a car and where traffic is perceived as dangerous. Although this type of organization of daily family life provides short term opportunities, it nevertheless has long term negative impacts on the acquisition of travel independence by children and adolescents.     

L’exploitation des données de cartes à puce à des fins de planification des transports collectifs urbains

Smart card fare collection systems are widely used nowadays in urban public transport networks. These systems are bound to facilitate the collection and management of revenues in transit authorities. However, since smart card systems collect a large amount of data on a daily basis, they can be exploited to better characterize the demand and supply of public transport in subways, tramways and bus networks, while data at an individual level should remain strictly confidential. The spatial and temporal dimensions of the data make it very interesting for planning purposes, but the data must first be validated and completed before further analysis. This article presents the results of five years of research conducted in collaboration with theSociété de transport de l??Outaouais, in Quebec. The following analyses are presented: error processing, estimation of alighting points, diffusion of operational statistics, analysis of user behaviour, analysis of network performance, comparison with household survey data and user loyalty modelling.     

Évaluation des potentiels de réduction des trafics automobiles dans le cas de la zone dense francilienne

The Pari 21 research project does not attempt to justify a move towards a radically different system—practically everything there is to say about the benefits and disadvantages of cars in cities has already been said. Instead, the project will perform simulations and assess, from the point of view of individuals, the feasibility of a transport system that is based mainly On the use of modes Other than the private car in the densely populated zone Of the Greater Paris Area (Paris city plus the inner suburbs). By constructing and evaluating transport policy scenarios, this research also aims to measure the potential for reducing car use in highly urbanized zones, particularly that which results from the reduction in journey speeds which are a likely consequence of the policies in question The method is based on repeated iterations of a simulation model which combines the assignment of round trips to modes other than the automobile with reformulations of transport supply. Demand is channelled towards personal modes (walking, cycling), public transport and a combination of personal and public modes. These iterations are based on the 1991-1992 Paris Region comprehensive travel survey which recorded all the round trips by car made in a typical day by the individuals living in the zone (i.e. the sequence of all trips made between each time the individual leaves home and returns home).     

Une caractérisation de l'émission acoustique des véhicules au cours des déplacements

Traffic noise is usually measured at fixed points whereas in reality vehicles move and generate noise throughout their trip. This paper therefore puts forward a new method of identifying noise emissions which takes account of the trip as a whole. We have made use of the concept of standard kinematic sequences (which are the elements which form all car trips) and have introduced a new acoustic index to characterize the noise emissions of a vehicle during a sequence. We have achieved this by adapting conventional highway acoustic indices to the way sequences are defined and used. We have calculated examples of these indices from acoustic recordings of isolated vehicles on a test track and from standard sequences.     

Structure des localisations intra-urbaines et mobilité domicile-travail

Rapid change in urban travel, in particular the increase in car traffic, is causing severe problems which mean that it is of strategic importance to understand the determinants of travel practices. In addition to such relatively familiar sociodemographic and economic parameters as gender, age and income, the characteristics of trips also depend on how the locations of intra-urban residences and economic activities are structured. The lengthening of distances and the increasing role of the car appear to be largely explained by the emergence of new, more sprawled, spatial configurations, which may even be multipolar. One of the ways of examining the link between urban forms and travel is to compare conurbations which differ very greatly in terms of the distribution of locations and determine to what extent these differences affect trip-making. The results we present here originate from on-going research, mainly by the Laboratoire d'dconomie des transports and INRETS, which compares the urban areas of Marseille and Aix-en-Provence, Lyon, Bordeaux, Grenoble, Dijon and Saint-Etienne. Only home-to-work trips have been considered. The first results suggest that there are significant differences between those urban areas which retain a pronounced centre and others which have been more affected by urban sprawl. The differences we have revealed with regard to home-to-work journeys involve the geography of traffic flows, the use of different modes of transport and above all the dissociation between residential locations and places of work, which is less marked in those areas where the centre has retained an important role.     

Vieillissement et gravité des atteintes lésionnelles des victimes d’accident de la circulation routière

This study uses the road traffic accident casualty register for the Rhône Département to investigate how the risk of severe or fatal injury varies according to age and to describe the injuries that explain the severity. Two groups of road users are investigated, car occupants and pedestrians. A NISS score of nine or over is taken to indicate a severe injury. Data analysis reveals that, for both groups, the risk of severe or fatal injury increases with age. The nature and location of the injuries depend on the age and sex of the victims. With regard to severe injuries, elderly female pedestrians are susceptible to fractures of the femur (and the femoral neck) and all parts of the upper limbs. Elderly male pedestrians are mainly exposed to fractures of the femoral neck. The greater vulnerability of severely injured elderly drivers results in thoracic injuries, which are partly explained by seat–belt wearing. The main cause of death, for pedestrians of all ages and young drivers is severe head injuries. Car occupants over the age of fifty more frequently suffer from severe thoracic injuries. These findings should not, however, be allowed to conceal the differences observed in the general population for the two severity criteria we have analyzed (severe injury or death). Mortality (in relation to the general population) is highest for young car occupants, while lethality (the fatality rate amongst those injured) is highest among the elderly. For pedestrians, both mortality and lethality increase with age. These findings are also applicable to the risk of severe injury. They justify the continuation of passive safety research in order to develop protection systems that are appropriate for the characteristics of car occupants. Furthermore, they should help to increase everybody’s awareness of the vulnerability of pedestrians and stimulate the introduction of preventive measures, particularly for seniors.     

Impact de la tarification,des fréquences et des temps de transfort sur les flux ferroviares dans le Bassin parisien

We have modelled trips on the Paris basin on the basis of the SNCF long-distance surveys. This modelling allows us to test the impact of pricing, journey times and train frequencies on rail travel demand. Three models have been constructed — a generation model (which computes trip production, that is to say the distribution of trips on the basis of the zones in which rail users reside), a geographical distribution model which is used to estimate the distribution of trip production on the basis of origin and destination zone, and lastly a model choice model which computes the proportion of commuting flows which takes place by rail. In this study the generation model has been partially supplied by the surveys. The distribution model takes thetrip production data output from the generation model in order to evaluate the total of rail flow on each O-D pair. This data is then used to calibrate the modal choice model.     

Les valeurs du temps des automobilistes à Marseille en 1995

Eighteen months after the urban tolled underground motorway Prado-Carénage tunnel was-opened in Marseilles (France), road-side interviews were conducted at both the tunnel entry and on the alternative roads. These Revealed Preference data provide a basis for an analysis of competition between a toll road and alternative free roads. In this paper, the binary choice fast toll road vs. free slow road is modelled with respect to the difference in travel time The model is a binary,logit model with a varying Value of-Time (VoT). Estimation by the Maximum Likelihood method shows a significant dispersion of the VoT, with a mean which is 30% higher than the median; it also shows that for a given travel time difference the dispersion in the VoTs explains two thirds of the variability in the path choice. Assuming that the competing roads only differ in price and time, a resulting mean VoT of 70 F/h (12 $/h) was estimated for a car driver during an urban trip in Marseilles in 1995. The first part of the paper introduces the behavioural assumptions in the microeconomic model. Then the data is analyzed and a log-normal distribution of the VoT is estimated. Lastly we indicate how to transfer the method and results to other studies.     

Comportements,personnalité, conduite des véhicules automobiles

This study was carried out on a population of 127 offending drivers of both sexes. A validation study was also performed on a sample of 51 offending drivers of both sexes. On the basis of a questionnaire that dealt with road related parameters (violations accidents, vehicle power) and use of the Guilford Zimmermann Temperament. Survey (with the Parenti driving questionnaire in the validation study), a variety of analyses were conducted which demonstrated essentially that offending drivers do not posses a specific psycholonical profile, (unlike motorcycle and HGV licence holders who do). However, it emerged that men and women have a different relationship with the car which is an object of narcissistic investment for men, contributing to their image and self-esteem and becoming a means or supporting and asserting their masculine identity) and that the intensification of male identity is associated with a variety of behaviours that increase the risk of both violations and accidents. Furthermore, while violations in themselves are not predictive of risk, perhaps revealing more about the nature of surveillance activities, frequent reoffending can lead to the assumption that the individuals are potentially dangerous drivers.     

Évaluation des logiciels critiques: application à la méthode B

From the point of view of safety the bottleneck in the operation of computerized systems currently appears to be the software. In order to improve the safety of software an independent assessment of its quality has been advocated for several years. The assessment of safety critical software consists of a technical examination on the basis of a set of criteria by a body which is independent from the designer. These assessment criteria are derived from the standards which are in force, the state of the art and experience. The objective of an assessments to verify that the product meets the specified safety and functionality requirements. In this paper the authors describe a combined approach to the assessment of safety critical software. On the one hand, the process used in order to develop the software is examined, and on the other the quality of the end product (software) is checked. The first part of the paper will present the position of safety critical software in the context of railway standardization as well as the main assessment techniques with particular reference to that used at Inrets. The second part of the paper will deal with the contribution of formal methods such as the B method to the development of safety critical software. The software assessment aspect will pay particular attention to assessment of the product — analysis of the traceability of requirements, integration and validation of safety properties. The paper ends with a brief account of the extraction and interpretation of metrics for a formal development. Finally the criteria used to assess the process are rapidly described. This approach has been used in the framework of an Esprit project known as Cascade (Certification and Assessment of Safety Critical Application Development).     

L'influence de la biactivité sur les stratégies spatiales des ménages

A survey conducted among staff at the University of Paris xii Val-de-Marne has shown that there are considerable differences in residential location and commuting strategies between those in one income households and those in two income households. This difference varies depending on social group. In the case of higher social groups, being in a two income household as opposed to a one income household increases the range of residential possibilities rather than the household's income per consumer unit, and in particular allows them to live nearer their work. In contrast, for low income groups, working couples commute considerably greater distances than persons in one income households. Thus, for lower income groups, belonging to a working couple mainly provides greater opportunities for home ownership, as an increase in distances to work does not affect journey times.