Climatisation automobile, énergie et environnement

In the first part of the paper the authors use data from measurement campaigns to demonstrate that automobile air conditioning significantly increases fuel consumption and emissions of regulated pollutants. Thus, under urban conditions, the average increase in consumption for both petrol and diesel vehicles is 3.1l/100km. Although the effects as regards pollutants vary from one model of vehicle to another, the increase in urban cycles is always very marked, in particular as regards NOx (+48%) and particulates (+64%) in the case of diesel vehicles. The paper then presents the results of test rig measurements of the mechanical and electrical energy consumption of air conditioning systems under different vehicle operating conditions (cycles) and for different thermal regimes of the air conditioning unit (depending on external temperature, the temperature set for inside the passenger compartment, etc.). The authors then present the results of pollutant emission and fuel consumption calculations for a passenger car with a 1.4 litre petrol engine fitted with a catalytic converter. These calculations were based on instantaneous data collected on the test rig. The conclusion is firstly that research and development is required to restric the power consumption of air conditioning which tends to increase urban pollution in particular during periods when high temperatures increase the likelihood of ozone peaks. The authors also draw the attention of the government to the need to consider air conditioning systems and other accessories in official emission and consumption measurements.     

Symbolisme pictographique et signalisation routière

Variable message signs (vms) are increasingly used on motorwaves for driver information purposes, No standards apply to the representation of symbols in discrete form by the lamp matrices of these signs. In addition, in the field, different modification (performed with varying degrees of success) of the non-discrete reference symbol are encountered This paper presents the results of trials conducted jointly by the lcpl and inrets which were intended to define the detail required for to represent continuous symbols using point matrices, The results will be used as a basis for drafting as standard that lays down rules for representing traffic signing symbols using vms. The same problem is raised in other European countries where vms use is also on the increaase. The development of new symbols that inform drivers about traffic conditions on major trans European roads has also been considered in order to create a universal language.     

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.     

Cheminements piétonniers et exposition au risque

Travel surveys do not include all walking activity. The techniques that are employed tend to underestimate the proportion of walking in daily travel, and pedestrian exposure to traffic accident risk cannot be accurately computed from the resulting data. To overcome these shortcomings, the authors have developed an original survey technique that involves following and observing subjects in the Greater Paris Region. Recording the subjects’ trips (paying particular attention to walking episodes) during an ordinary day provides precise values for risk exposure that distinguish between the on-road and off-road components of walking activity. A number of different risk ratios are then computed, according to the geographical location and whether the pedestrian is walking on or off the road. These risk ratios are then compared to those that apply to motorists.     

Choix modal et valeurs du temps en Île-de-France

This paper estimates values of time in the Paris region by investigating modal choice. It uses survey data from the 1997 Enquête globale de transport and results from simulation using the model developed by the IAURIF (Institut d'aménagement et d'urbanisme de la région Île-de-France). Initially, the authors applied conventional Logit and Probit models to give estimates for groups of users based on age, gender, income and geographic variables relating to the location of their residence and work. In general our values of time are higher than the official figure. Two extensions of the basic models were then tested. First, with a Mixed Logit model, the heterogeneity of users was considered, then ER-logit model was applied to examine income effects. The main finding is the extent to which the income effect modifies values of time estimates. The paper also presents a separate distribution of values of time for car users and public transport users and an assessment of the proportion of their income that users take into account when selecting a transport mode.     

Mobilité et accès à la voiture chez les personnes âgées: Évolutions actuelles et enjeux

In France, and in most other industrialised countries, demographic ageing means that in the next decades there will be a rise among the elderly in vehicle ownership and driving for daily trips, long distance travel and leisure trips. This paper demonstrates the existence of these trends by drawing on a variety of statistical sources — National Transport and Communication Surveys, Urban Household Travel Surveys (Lyon) and surveys on French holiday practices. We nevertheless demonstrate that this structural change exhibits a high degree of differentiation with regard to gender, household income, place of residence and state of health. This change, which increases car use, is expected to continue during the next few years, especially among elderly women. Long term changes in lifestyles encourage the view that in the future people will cease to drive at a more advanced age. The increase in car use has important long-term implications in two areas. On the one hand it will affect road safety, on the other hand it raises the issues of the sustainability of mobility and the obligation to meet the needs of persons who are no longer able to drive.     

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.     

Les systèmes de transmission sol-train état de l'art et perspectives

Intelligent transportation systems aim to provide comprehensive improvements to the efficiency and safety of transportation systems by applying new information and communication technologies. Such techniques are increasingly used for guided transport, bringing this into the domain of intelligent transportation. The functions involved in the movement of trains which were formerly performed by drivers and staff on the ground are now performed by means of fail-safe automatic devices which are controlled by transmissions between the track and the train. Ultimately, the development of intelligent transportation therefore involves total replacement of the driver, as has been the case since 1983 in the first French automatic metro, the val in Lille. This example was followed by ordival at Orly, maggaly in Lyon, the val in Toulouse finally, and most recently in October 1998, ratp line 14 in Paris, known as meteor. This paper describes voice and data track-to-train transmissions for train control command and safety purposes and also in order to satisfy the demands of passengers. The principal applications of track-to-train transmissions are covered as are the technologies employed. The increase in requirements and in the functions performed by automatic devices and the objectives of improving performance and increasing train speeds have resulted in the development of a new European train control-command system, the most advanced version of which is essentially based on track-to-train radio communications. This new system, which was principally developed for high speed train systems is being viewed with increasing interest by urban and suburban guided transport networks. At the same time, the remarkable growth to the mobile telecommunications market has led to the emergence of new needs, linked to the improvement of the services provided to passengers.     

Entre marche et métro, les mouvements intra-urbains des touristes sous le prisme de l’? adhérence ? à Paris et en ?le-de-France

The urban movement of tourists remains largely unknown, but the mobility of tourists contributes to the metropolitan process. Around the notion of ??adherence??, this article demonstrates how, in the Paris metropole, tourists rely mainly on walking and the use of the tube to travel within the city. The structurally different characteristics of walking and the use of the tube represent a theoretical opposition between the two types of movements that are differently ??adherent?? to the city. However, these mobilities complement each other. Indeed, the partial disconnection of the tube is addressed by the direct connection and proximity to the city allowed by the pedestrian means.