bluuebunny/crossref_metadata_2025 huggingface dataset:
CFD Modelling of Hydrogen-Fueled SI Engines for Light-Duty Applications
Authors: Ramognino Federico , Sforza Lorenzo , D'Errico Gianluca , Gomez-Soriano Josep , Onorati Angelo , Novella Ricardo
Published: August 2023

The employment of hydrogen as energy carrier for transportation sector represents a significant challenge for powertrains. Spark-ignition (SI) engines are feasible and low-cost devices to convert the hydrogen chemical energy into mechanical work. However, significant efforts are needed to successfully retrofit the available configurations. The computational fluid dynamics (CFD) modelling represents a useful tool to support experiments, clarifying the impact of the engine characteristics on both the mixture preparation and the combustion development. In this work, a CFD investigation is carried out on typical light-duty SI engine configurations, exploring the two main strategies of hydrogen addition: port fuel injection (PFI) and direct injection (DI). The purpose is to assess the behaviour of widely-used numerical models and methodologies when hydrogen is employed instead of traditional carbon-based fuels. First, the DI process is investigated on a research pent-roof SI engine, in which hydrogen is introduced by a single-hole injector. Numerical simulations are carried out to understand the behaviour of two turbulence models and two mesh resolutions on the prediction of the hydrogen stratification, when a non-oriented hexahedral-dominant mesh is employed with layer addition-removal for the piston motion. Results show how the experimental jet penetration is properly predicted by both selected turbulence models, while high mesh resolutions in the injection region allow to capture the shock-waves dynamics of the under-expanded jet but they have negligible effects on the global mixture stratification. Then, the PFI operation is analyzed on a pent-roof single-cylinder SI engine under highly diluted hydrogenair mixtures. Experimental measurements are used to assess the impact of both the laminar flame speed and the flame-wall interaction modeling, with no fuel stratification. Results clarified that in presence of ultra-lean conditions the correlations for the laminar flame speed prediction are more restrictive than the tabulation approach, while higher mesh refinements at walls improve the heat losses prediction.
Methanol Evaporation in an Engine Intake Runner under Various Conditions
Authors: Pu Yi-Hao , Larsson Tara , Robeyn Tom , De Paepe Michel , Verhelst Sebastian
Published: August 2023

Methanol has recently emerged as a promising fuel for internal combustion engines due to its multiple carbon-neutral production routes and advantageous properties when combusting. Methanol is intrinsically more suitable for spark-ignition (SI) operation thanks to its high octane number, but its potential in heavy-duty applications also encourages engine manufacturers in this field to retrofit their existing compression-ignition products into methanol/diesel dual-fuel (DF) operation. For both SI operation and DF operation, injecting methanol into the engine’s intake path at low pressure is a relatively simple and robust method to introduce methanol into the cylinders. However, the much higher heat of vaporization (HoV) of methanol compared to conventional SI fuels like gasoline can be a double-edged sword. On the one hand, its enhanced cooling effect may increase volumetric efficiency and lower knock tendency, on the other hand, the extra heat it absorbs when evaporating may pose cold-start issues and lead to unstable combustion. To further investigate, a special experimental setup was built. Multiple thermocouples were mounted on an intake runner where the fuel is injected to monitor the temperature changes of the flow before and after injection. The temperature of the runner itself was also monitored to assess the heat taken from the metal wall of the runner pipe. Different air-fuel ratios, air temperatures, air pressures, and air mass flow rates were tested to evaluate their influences on methanol evaporation. The test results were then compared with conventional gasoline operation. It was found that the temperature drop after fuel injection is strongly dependent on the flow temperature, and that the evaporated fraction of methanol was far lower than that of gasoline even with higher flow temperature. Their very different evaporation behaviors are thoroughly discussed.
Numerical and Experimental Investigation on Passive Prechamber Configurations Able to Operate at Low Engine Speed and Load
Authors: Gianetti Giovanni Gaetano , Lucchini Tommaso , Sforza Lorenzo , Onorati Angelo , Lombardi Claudio , Cavagnero Carlo
Published: August 2023

Turbulent Jet Ignition (TJI) represents one of the most effective solution to improve engine efficiency and to reduce fuel consumption and pollutants emission. Even if active prechambers allow a precise control of the air-fuel ratio close to the spark plug and the ignition of ultra-lean mixtures in the main chamber, passive prechambers represent a more attractive solution especially for passenger cars thanks to their simpler and cheaper configuration, which is easier to integrate into existing engines. The main challenge of passive prechambers is to find a geometry that allows to use TJI in the whole engine map, especially in the low load/speed region, without the use of a second sparkplug in the main chamber. To this end, this works reports a CFD study coupled with an experimental investigation to overcome this limitation. A baseline prechamber configuration able to operate in the whole engine map was firstly studied using the CFD models and validated against the experimental results of a 2.0 L spark-ignition (SI) engine at different equivalent ratios. After the assessment of the proposed approach, different prechamber configurations were investigated to find a proper geometry able to produce similar results of the baseline configuration but with a different spark-plug installation to allow an easier integration into existing engines.
CFD Analysis of Different Biogas Upgrading Levels for Dual-Fuel Operation in Diesel Engines
Authors: Zucareli de Souza Túlio Augusto , Frez Gustavo V. , Pinto Gabriel , Costa Roberto , Roque Luis Filipe A. , Coronado Christian J. R. , Vidigal Luís Pedro V.
Published: August 2023

As the transportation sector continues to increase its energy demand and present stricter environmental regulations, the use of biofuels has been gaining more attention. Among them, one of the most promising options is biomethane - a methane-rich fuel produced from biogas upgrading. Despite presenting excellent combustion properties and composition comparable to natural gas, this green fuel requires a proper biogas processing technology that may lead to a high final cost. On the other hand, the direct use of unprocessed biogas may cause operational issues in the engine, since it may present corrosive contaminants and a high CO2 concentration that affects the combustion and decrease storage efficiency. Therefore, a balance between upgrading level and good engine operation could lead a reliable engine performance without the need of high processing costs. In this sense, the present study aims to discuss the effect of different biogas upgrading levels over engine performance and pollutant formation, focusing on fuels with distinct methane concentrations and their use as a partial energy source in dual-fuel diesel engines. For this analysis, a CFD simulation was carried out using a multi-component, 178-species reaction mechanism, which was experimentally validated for biogas and biomethane at various energy substitution fraction (ESF). Compared to diesel operation, all tested fuels led to delayed combustion, more homogeneous temperature profiles, and lower NOx emissions. Biogas upgrading level did not visually affect temperature and NOx distribution inside the cylinder, but final NOx emissions were up to 24.2% lower for biogas with lower methane concentrations. Finally, slightly delaying the diesel injection led to lower NOx, lower UHC, and increased power, but the optimal delay was lower for dual-fuel operation due to the delayed combustion of both biogas and biomethane.
Development of a Laboratory Unit to Study Internal Injector Deposits Formation
Authors: Pach Mayte , Hittig Henrik , Scholle Tobias , Kusar Henrik , Engvall Klas
Published: August 2023

The formation of deposits in the fuel systems of heavy-duty engines, using drop-in fuels, has been reported in recent years. Drop-in fuels are of interest because they allow higher levels of alternative fuels to be blended with conventional fuels that are compatible with today’s engines. The precipitation of insolubles in the drop-in fuel can lead to clogging of fuel filters and internal injector deposits, resulting in increased fuel consumption and engine drivability problems. The possible mechanisms for the formation of the deposits in the fuel system are not yet fully understood. Several explanations such as operating conditions, fuel quality and contamination have been reported. To investigate injector deposit formation, several screening laboratory test methods have been developed to avoid the use of more costly and complex engine testing. To further evaluate and understand the formation of internal injector deposits in heavy-duty engines, a thermal laboratory test method has been developed. The test method is called Thermal Deposits Test (TDT) and it is inspired by Jet Fuel Thermal Oxidation Test (JFTOT) method. This test unit can be used to study in applications where a fluid is in contact with a hot surface. The method uses common laboratory hardware and readily available off-the-shelf parts, making it inexpensive to build and very flexible to operate. Deposits are collected on a metal foil, which makes it easier to analyze. This paper describes the construction of the apparatus and its performance. Experimental tests with diesel fuel, doped with soap-type soft particles, which contain typical particles that can form deposits, are performed, and compared with JFTOT results. Analytical techniques, such as Scanning Electron Microscopy with Energy Dispersive X-Ray, Fourier-transform Infrared Spectroscopy, and Pyrolysis coupled with Gas Chromatography-Mass Spectroscopy and Ellipsometry were used. Conclusions about the performance of the doped fuel are drawn from the test. Future plans are to study the mechanisms behind the formation of internal diesel injector deposits.
Improvement of Post-Oxidation for Low-Emission Engines through 3D-CFD Virtual Development
Authors: Pipolo Mario , Kulzer Andre , Chiodi Marco , Moriyoshi Yasuo
Published: August 2023

There is a growing need for low-emissions concepts due to stricter emission regulations, more stringent homologation cycles, and the possibility of a ban on new engines by 2035. Of particular concern are the conditions during a cold start, when the Three-Way Catalyst is not yet heated to its light-off temperature. During this period, the catalyst remains inactive, thereby failing to convert pollutants. Reducing the time needed to reach this temperature is crucial to comply with the more stringent emissions standards. The post oxidation by means of secondary air injection, illustrated in this work, is a possible solution to reduce the time needed to reach the above-mentioned temperature. The strategy consists of injecting air into the exhaust manifold via secondary air injectors to oxidize unburned fuel that comes from a rich combustion within the cylinder. This strategy can be implemented without major modifications to the engine's hardware or control system, making it an attractive option for retrofitting older engines or incorporating into new designs. The investigation was conducted experimentally and numerically, with test bench measurements and 3D-CFD simulations. The test bench data were helpful for validating and calibrating the 3D-CFD simulations, which employ two interrelated approaches. The first approach utilizes a full-engine mesh, which includes a 0D turbocharger model, to extrapolate reliable boundary conditions. The second approach uses a detailed exhaust model that includes the mentioned accurate boundary conditions and a chemical reaction mechanism. This paper presents the effects of post oxidation in two different engine operating points. Various secondary air injection strategies, including different temperatures and mass flows, and an alternative exhaust manifold design, are evaluated to assess potential improvements in post oxidation by means of 3D-CFD virtual development.
The Potential of On-Board Data Monitoring for the Characterization of Real-World Vehicle Fuel and Energy Consumption and Emissions
Authors: Dimaratos Athanasios , Kontses Dimitrios , Doulgeris Stylianos , Zacharof Nikiforos , Keramidas Arsenios , Stamos Georgios , Papageorgiou-Koutoulas Alexandros , Samaras Zissis
Published: August 2023

The upcoming Euro 7 regulation introduces the concept of continuous On-Board (emission) Monitoring (OBM), while On-Board Fuel/Energy Consumption Monitoring (OBFCM) is already an integral part of modern vehicles. The current work aims to assess whether on-board data could provide sufficient information to characterize real-world vehicle performance and emissions. Nine Euro 6d-ISC-FCM passenger cars were used, covering a wide range of powertrain technologies, from conventional gasoline and diesel to hybrid (HEV) and plug-in hybrid (PHEV) electric vehicles. Three vehicles were thoroughly tested in the laboratory and on the road, aiming at evaluating in detail the on-board data monitoring system. The evaluation concerned OBFCM device recordings of fuel consumed and distance travelled, as well as tailpipe NOx emissions and exhaust mass flow rate. Four vehicles were monitored for two weeks under real-world operation, while a diesel and a gasoline PHEV have been monitored for approximately two years. The collected data provided information on the evolution of fuel/energy consumption, highlighting the impact of parameters like season, mileage accumulation and charging behavior. The findings reveal good accuracy of the OBFCM device, with the lifetime fuel consumed deviation remaining below 5% in the Worldwide harmonized Light vehicles Test Cycle (WLTC) and slightly exceeding that threshold on the road in limited cases, while distance travelled deviations were negligible. Regarding NOx emissions, the tailpipe levels calculated using the on-board data were within ±10% compared to reference values, with the final deviation attributed to the combination of the inaccuracies of the sensor and the exhaust mass flow determination. Further findings of the mid/long-term monitoring activity highlighted the strong potential of on-board data to provide a realistic picture of vehicle operation under any driving conditions, e.g., evolution of the fuel/energy consumption and the real-world gap between laboratory and real-world values, characterization of the brake energy recuperation strategy of vehicles with different electrification levels and the identification of Diesel Particulate Filter (DPF) regeneration and of the corresponding NOx emissions.
Modeling and Experimental Validation of a Hybrid Electric Propulsion System for Naval Applications
Authors: Marialto Renato , Brando Gianluca , Dannier Adolfo , Sementa Paolo , Cardone Massimo , Fornaro Enrico
Published: August 2023

Focusing on coastal or inland navigation cities, where emissions from ships are not negligible concerning global ones, the possibility of reducing exhaust gas pollution would have more benefits for public health and air quality. Therefore, in recent years, increasing attention on environmental sustainability is driving the shipbuilding industry towards greener propulsion based on full-electric or hybrid-electric propulsion systems. This work is presented a parallel hybrid system composed of two electric motors, one internal combustion engine, and lithium battery storage. All motors are coupled to the propeller through a specially designed transmission system based on the High Sliding Gear theory (HSG). The hybrid-electric propulsion system is designed to extender the battery pack durability, ensuring a smooth profile of the required current, through the complementary action of the batteries and the internal combustion engine. Then, the overall performance of the hybrid propulsion system is verified by laboratory experimentations, also testing the energy storage system. A fast boat (yacht) is chosen as a simulation case where a lumped parameters model is coupled with map-based motors obtained from experimental test activities performed on this hybrid propulsion system. This model is also validated by the available performance data obtained during an experimental campaign where has been emulated a typical propeller load. The results show the feasibility of this hybrid architecture, in terms of performance and sustainable maritime transport. Furthermore, the simulation results confirm the experimental performance, proving to be a good tool for system development in terms of energy management.
Fuel Consumption Potential Gains of Rankine Thermal Power Recovery for Series Hybrid Electric Vehicles
Authors: Cottin Willy , Colin Guillaume , Moreira Mickaël , Houillé Sébastien , Bou Nader Wissam , Charlet Alain
Published: August 2023

Considerable efforts have been made in the automotive industry on powertrains in order to minimize the energy required by passenger cars. This can be done by improving factors such as the technologies used and the way the energy is used.Losses can be recovered from thermal irreversible power sources. The lost energy contained in the exhaust gases and the coolant can be recovered using two Rankine Machines. As Rankine Cycles work better on a stabilized operating point, a Series Hybrid Electric Vehicle (SHEV) would appear to have a great potential for this technology. The two Rankine machines can be chained: the high temperature machine recovers the lost exhaust gases energy, while the low temperature machine recovers both the lost energy coming from the coolant plus the energy coming from the low temperature side of the previous machine. In order to be sure to estimate the maximum potential gains from the use of chained Rankine machines on SHEVs, the degrees of freedom are optimised to maximize irreversible power source efficiency. Moreover, using optimal control theory is essential to minimize the overall vehicle energy consumption. Here, optimal control is used with dynamic programming that takes into account the battery state of charge dynamics. The architecture of chained Rankine machines has been tested for different atmospheric conditions. Simulation results show an average energy reduction of 20%.
CFD Simulations and Potential of Nanofluids for PEM Fuel Cells Cooling
Authors: D'Adamo Alessandro , Corda Giuseppe , Berni Fabio , Diana Martino , Fontanesi Stefano
Published: August 2023

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are undergoing a rapid development, due to the ever-growing interest towards their use to decarbonize power generation applications. In the transportation sector, a key technological challenge is their thermal management, i.e. the ability to preserve the membrane at the optimal thermal state to maximize the generated power. This corresponds to a narrow temperature range of 75-80°C, possibly uniformly distributed over the entire active surface. The achievement of such a requirement is complicated by the generation of thermal power, the limited exchange area for radiators, and the poor heat transfer performance of conventional coolants (e.g., ethylene glycol). The interconnection of thermal/fluid/electrochemical processes in PEMFCs renders heat rejection as a potential performance limiter, suggesting its maximization for power density increase. To this aim, suspensions of coolants and nanoparticles (nanofluids) have been proposed for PEMFCs cooling, although their characterization has often been limited to the superior thermal conductivity, overlooking a comprehensive understanding, and leaving a relevant research gap.

In this paper, nanofluids cooling is simulated using 3D-CFD in a small laboratory scale (25 cm2) model of a hydrogen-air PEMFC with a liquid cooling circuit. The variation of the coolant fluid is studied considering flow uniformity, heat rejection, pressure losses, and power generation, ultimately leading to a high-level analysis on the trade-off between heat transfer/storage, relevant for coolant channels in PEMFCs. The study elucidates the membrane conditions and the compositional requirements for ethylene glycol and water based nanofluids to lead to a net gain in the generated power density, modelled in the range of +5/10% for high particle loading (10%) and envisaged to reach +15% for hypothesized ideal compositions. The study clarifies the role of nanofluids for PEMFC cooling and redefines their enabler contribution in the development of high power density PEMFCs, indicating guidelines for their application-designed formulation.
Real-Time Prediction of Fuel Consumption via Recurrent Neural Network (RNN) for Monitoring, Route Planning Optimization and CO2 Reduction of Heavy-Duty Vehicles
Authors: Pandolfi Alfonso , Adinolfi Ennio Andrea , Polverino Pierpaolo , Pianese Cesare
Published: August 2023

This article presents a novel approach for predicting fuel consumption in vehicles through a recurrent neural network (RNN) that uses only speed, acceleration, and road slope as input data. The model has been developed for real-time vehicle monitoring, route planning optimization, cost and emissions reduction and it is suitable for fleet-management purposes. To train and test the RNN, chosen after addressing several structures, experimental data have been measured on-board of a heavy-duty truck representative of a heavy-duty transportation company. Data have been acquired during typical daily missions, making use of an advanced connectivity platform, which features CANbus vehicle connection, GPS tracking, 4G/LTE - 5G connectivity, along with on-board data processing. The experimental data used for RNN train and test have been treated starting from on-board acquired raw data (e.g., speed, acceleration, fuel consumption, etc.) along with road slope downloaded from map providers. The improvement of the network performance has been achieved through a weight pruning procedure, to minimize instabilities and error amplification during fuel consumption prediction. RNN training has been performed using only one scheduled mission for both vehicles, but to distinct models (i.e., one for the bus and one for the truck) has been designed and tested on various routes, showing high accuracy in fuel consumption estimation. The achieved results proved RNN being capable of improving fuel consumption prediction on simulated routes, utilizing only few inputs, to support fleet operations in advanced route planning, with lower operating expenses and therefore reduced pollutant emissions.
À propos de "Quelques réflexions sur la notion d’accessibilité"
Authors: Koenig G.
Published: August 2023

Commentaire de l’article de Renaud de Crecy, "Quelques réflexions sur la notion d’accessibilité"
Deux problèmes dans la modélisation du comportement de déplacement
Authors: Klaassen L.H. , Paelinck J.H.P.
Published: August 2023

Transport behaviour so far has not been adequately integrated in spatial models. Two aspects of the problem are studied here: realistic measures of distance in spatial production models, and the influence of distance on the behaviour of buyers as far as the place of purchase are concerned.

Les comportements en matière de transports n'ont été qu'imparfaitement intégrés dans les modèles spatiaux. Deux aspects du problème sont étudiés ici : des mesures réalistes de distances dans les modèles de production spatialisés, et l'influence des distances sur le comportement des acheteurs en matière de choix du lieu d'achat.
Une méthodologie d'analyse de la relation mobilité programme d'activité
Authors: Bonnafous Alain
Published: August 2023

In a part one, are presented the problem of the analysis of statistical informations on individual activity program, and the DECORTYC method of data analysis which we used until now on this sort of problem. Nevertheless in this case, there is an impossibility to applicate this method and we explain why. In a second part, a derivated method is described (with photographical illustrations) as a solution to the both problems of the aggregation of the individual behaviour and of the articulation between lived-space, lived-time, and mobility. In the last part, we give an example as an illustration of the possibilities of this method of the "fichier-image DECORTYC".

Dans une première partie sont abordés les problèmes d'analyse de données sur les programmes d'activité et la méthode DECORTYC que nous utilisions jusqu'ici pour ce type d'analyse. Cependant, il y a dans ce cas une incompatibilité entre les données et cette méthode. Une méthode dérivée est donc présentée avec des illustrations photographiques dans une deuxième partie. Elle résout les deux principaux problèmes : l'agrégation des observations individuelles et l'étude de l'articulation entre espace vécu, temps vécu et mobilité. Dans la dernière partie, nous présentons une illustration des possibilités de la méthode du "fichier-image DECORTYC".
Taking into account of demand and anarchic development of networks
Authors: Le Diberder Alain
Published: August 2023

Founded on a study of the french telecommunications development, this paper tries to enlighten two questions: at first, the problem of the ideological and political framework in which is inserted the public management of the network's development. The current solution would need, to be consistent, the anteriority or, at least, the independence of the demand from the public supply. But it appears that the public power, main manager of the supply, is also the main centre of specification of the demand.From this point follows a second one, more pragmatic: public enterprises use to estimate the demand through a system of filters, the working of which is leading to an irregular development of the network, an conséquently an expansive development, it would be certainly useful to settle some "short circuits" in the demand estimation system and for that to re-examine the place of demand in the network manager's strategy.

Basé sur une étude du développement des télécommunications françaises, cet article tente d'éclairer deux questions : d'abord celle du cadre idéologique et politique à donner à la gestion par l'Etat du développement des réseaux. La réponse passe par une lecture du droit administratif à l'issue de laquelle il apparait que les bases actuelles de la justification de l'intervention de l'Etat dans ce domaine sont incertaines : la notion de Service Public impliquerait en effet qu'une demande de réseaux soit préalable à l'intervention de l'Etat. Or il apparait que la puissance publique, principale gestionnaire de l'offre, joue également le rôle moteur dans la formulation de la demande.De ce premier point en découle un second, plus pragmatique : les entreprises publiques n'apprécient ici la demande qu'à travers un système de filtres, dont le fonctionnement conduit à un développement heurté, et donc coûteux, des réseaux. Il serait sans doute utile d'imaginer des "circuits courts" d'appréciation de la demande de réseaux, et pour cela de replacer cette demande au centre des stratégies de ces entreprises.
Un instrument d'analyse des chaînes de transport : le concept de trajet
Authors: Bernadet Maurice
Published: August 2023

Analysis of goods transport chains - i.e. use of a succession of different modes of transport -needs to cut out trips and "break of load" points. Usually, trips are defined by singleness of mode, and "break of load" points by mode-to-mode transfer operations. An other way to cut out more thinly is proposed in terms of "journey". A "journey" is defined by three criterions: i) geographical displacement of goods ii) use of one and the same vehicle iii) trip is realized by one the same operator. This operational use concept is presented, and discussion turns on signification of these three criterions.

L'analyse des chaînes de transport repose sur un découpage distinguant les déplacements et les points de rupture de charge. Généralement les déplacements sont définis par l'unicité du mode utilisé, et les points de rupture de charge par les opérations qui permettent le transfert d'un mode à l'autre. Un découpage plus fin est proposé, en recourant au concept de "trajet". Un trajet est défini par trois critères : - un déplacement géographique de la marchandise - l'emploi d'un seul et même véhicule - la réalisation du déplacement par un seul et même opérateur. L'article présente ce concept à vocation opérationnelle et discute de la signification de ces trois critères.
Some reflexions related to the evaluation of quality service in transportation of goods
Authors: Bernadet Maurice
Published: August 2023

Analysis of competition between modes or between carriers on goods transport market refers very often to the concept of "quality of service", without any precise definition of this concept.Quality of service of transport operation may be characterized by its position in a multidimensional space, the axes of which measure speediness, regularity, safety and, finally, production of informations linked to goods movements. Moreover, when a shipper chooses a carrier, it takes into account its "adaptability" (ability to assume services of various characteristics) and its "logistic ability" (ability to conduct operations related to transport, in the strict sense of the word).

L'analyse de la concurrence entre modes ou entre transporteurs sur le marché des transports de marchandises fait souvent référence à la notion de qualité de service que l'auteur précise ainsi : on peut caractériser la qualité de service d'un transport en le positionnant dans un espace multidimensionnel dont les axes mesurent la rapidité, la ponctualité, la sécurité et enfin la production d'informations liées à la circulation des marchandises. En outre lorsqu'un chargeur choisit un transporteur, il tient compte de son "adaptabilité" (aptitude à assurer des prestations de caractéristiques différentes) et de son "aptitude logistique" (aptitude à assurer des opérations connexes au transport proprement dit).
Short trips: how, why and who? A study on the urban area of Lyons
Authors: Diaz Olvera Lourdes , Plat Didier
Published: August 2023

In transport planning, when efforts are undertaken in order to re-activate life in the ancient "quartiers" or to limit energy consumption, attention is frequently paid to short trips. However, this field still remains quite unexplored.This paper tries to approach short trips through an original trip classification based not only on the distance travelled but also on some of the characteristics of the chain to which the trip belongs. Then, it's possible to study the modal split, to show the close relation between trip purpose and type of trip, and finally, to reveal some socio-economic determinants of this micro-mobility.

Qu'il s'agisse d'essayer de redonner vie à des quartiers ou de rechercher des économies d'énergie dans les transports urbains, l'attention se porte bien souvent sur les déplacements courts. Mais ceux-ci restent encore mal connus.Cet article tente de les cerner à l'aide d'une typologie originale des déplacements. Elle repose en effet non seulement sur la distance du déplacement lui-même mais aussi sur certaines caractéristiques de la sortie à laquelle il appartient. Il est ainsi possible d'étudier leur répartition modale, de mettre en évidence des liaisons fortes entre motif et type de déplacement et enfin de déceler quelques déterminants socio-économiques de cette micro-mobilité.
Optimal calculation of the infrastructure in multi-regional development
Authors: Paelinck Jean-Henri-Paul
Published: August 2023

This article shows how a combination of spatial econometrics and mathematical programming allows of selecting optimal regional action programmes. The applica¬tion concerns regions of the EC of the nine.

Cet article montre comment une combinaison d'économétrie spatiale et de programmation mathématique permet de sélectionner des programmes optimaux d'action régionale. L'application a trait à des régions de la CE des neuf.
Polar networks: framework for evaluating performances
Authors: Amar Gorges , Stathopoulos Nikos
Published: August 2023

The traditional concept of network (which we have named for commodity reasons, "tube-network") is today in crisis. Based on a hydraulic like approach, it is no more able to describe phenomenas like diversification of transportation mobiles, complexification of urban territories, problems of "modes integration" strategies in urban transportation, etc. In the same time the elements of a new conceptual paradigm (which we have called "connexionist") are beginning to appear. Remodeling RATP's bus networks is today a priority objective for the enterprise. The aims and principles of this restructuration have been developed in a project which is based on a connexionist conception of networks. Evaluating performances of this type of networks supposes the development of new formal models. This paper presents a research in this matter, founded on system analysis and multicriteria supporting decision theory.

Le concept traditionnel de réseau (que l'on appelle par commodité «réseau-tuyau» est aujourd'hui en crise. Inspiré d'une problématique hydraulique, il n'arrive plus à rendre compte de phénomènes tels que la diversification croissante des motifs et des pratiques de déplacement, la complexification des territoires urbains, l'échec relatif des stratégies d'intégration des modes, etc. C'est ainsi que les projets de la RATP pour la restructuration de son réseau-bus en banlieue, font appel aux notions de pôle territorial, de connexion et se rapprochent ainsi du paradigme de conception de réseau que l'on a appelé «connexionniste». Évaluer les performances d'un réseau de ce type, suppose que l'on puisse le formaliser conceptuellement et en faire une modélisation. Cet article présente les réflexions développées à ce jour, à propos de ce problème, par la Mission PROSPECTIVE de la RATP et essaie en même temps de proposer un cadre pour la suite des recherches.
The automobile markets and their variations for new and used vehicles
Authors: Madre Jean-Loup
Published: August 2023

From the automobile market analysis between 1973-1987, it appears that the part of new cars decreases compared with used cars, on account of increasing time ownership and propensity to take second-hand cars.Buyer’s caracteristics (more than one car owning, household income. age) have great effects on the market trend.Long run, the part of new cars should decline, but more slowly, with population ageing and purchasers decreasing (for first or second car, generally second-hand car). However, the generalization of vehicles technic control should much change the car market equilibrium.

L'analyse du marché de l'automobile de 1973 à 1987 montre que la part du neuf tend à diminuer par rapport à l'occasion, avec l'allongement des durées de possession des véhicules et la tendance au remplacement par l'occasion.Les caractéristiques des acheteurs (multi-motorisation, situation financière des ménages, âge) influent beaucoup sur l'évolution des marchés.À long terme, la baisse de la part du neuf devrait continuer, mais à un rythme ralenti en raison du vieillissement de la population et de la baisse de la proportion d'accédants (passage à la seconde voiture ou accès à la motorisation, généralement par l'occasion). Toutefois, la généralisation du contrôle technique des véhicules pourrait beaucoup modifier l'équilibre de ces marchés.
TGV spread effects analysis
Authors: Muller M. , Papinutti Marc , Reynaud Christian
Published: August 2023

In 1981, the TGV was put on service. In 1986, the impact on the journeys is both more permanent and larger than it was supposed: after noticing a strong induction phase and a new modal share, one may say that the growth of rail, air and car traffics is still important on the Paris-South-East corridor. This growth goes with an important space sprawl: the main TGV served cities are concerned with the appraisal for the TGV network.The OEST was in charge of these main effects analysis, based on two complementarily origins:- Monthly traffic statistics allowing an accurate chronological analysis;- Air, rail and car inquiries done in 1981 and 1984 drawing the modal share of the ante and post TGV situation.It comes out from these analysis that the general success result of a great diversity of situations: the transport demand increased strongly where as it was deeply modified.At the moment, the advance in knowledge comes us against a problem of relevance as for the available data in order to quantify the phenomenon. Based on the South-East TGV experience, the paper focuses on the method problem for the data collecting.

Six ans après sa mise en service, il apparaît que l'impact du TGV sur les déplacements est à la fois plus durable et plus large que prévu : après avoir observé une phase de forte induction et une nouvelle répartition entre modes, la croissance des trafics ferroviaires, aériens et autoroutiers reste vigoureuse en 1987 sur l'axe Paris-Sud-Est.Cette croissance s'est accompagnée d'une diffusion dans l'espace : les grandes villes du Sud-Est, désormais reliées à Paris par le TGV, sont concernées par la mise en place d'un début de réseau TGV.L'étude de ces deux types d'effets a été menée à l'OEST à partir de deux sources complémentaires, l'une (comptages mensuels sur l'axe) permettant une analyse temporelle fine, l'autre (enquêtes coordonnées faites en 1981 et 1984) donnant une photographie de la structure intermodale du trafic avant et après TGV. Il ressort de ces analyses que le succès général résulte d'une grande diversité de situations : la clientèle ferroviaire a fortement augmentée mais en se modifiant profondément.À l'heure actuelle, la progression des connaissances se heurte à un problème de pertinence des données disponible pour quantifier le phénomène. À partir de l'expérience du TGV Sud-Est, l'article soulève les problèmes de méthodes dans la collecte de données.
About some functional location models
Authors: Paelinck Jean-Henri-Paul
Published: August 2023

The present study bears on a generalization of the weberian location problem to the various divisions of a firm, linked together and with their respective markets through their respective transport and communication costs; the study is completed by spatial econometrics considerations (test, estimation).

La présente étude s'attache à généraliser le problème wébérien de localisation à différentes divisions d'une entreprise, liées entre elles et avec leurs marchés respectifs par leurs coûts de transport et de communication respectifs ; l'étude est complétée par des considérations d'économétrie spatiale (test, estimation).
Diesel Cars and Traffic Growth
Authors: Madre Jean-Loup
Published: August 2023

Since the mid-1980s there has been a rapid to diesel-engine cars and a significant increase in road traffic in France. Are these two phenomena related?- detailed data show that a diesel vehicle replacing a petrol one has a higher annual mileage (and a petrol vehicle replacing a diesel one has a lower mileage), but that the total mileage of the household remains almost constant;- the distribution of total annual mileage for both diesel and for petrol vehicles has remained almost unchanged since 1985.Therefore, the growth in the proportion of diesel vehicles is the principal explanatory — most of the behavourial factors have remained stable.

Depuis le milieu des années 80 en France, on constate simultanément une diésélisation rapide du parc automobile et une croissance importante de la circulation. Ces deux phénomènes sont-ils liés ?- sur données individuelles, on observe qu'un diesel remplaçant une voiture à essence roule davantage (et réciproquement), mais le kilométrage total du ménage varie peu ;- les distributions de kilométrage pour le diesel et pour l'essence restent à peu près constantes au cours du temps.Le principal facteur d'évolution est donc la progression de la part des véhicules diesel dans le parc ; la plupart des structures de comportement restent stables.
Le système expert en géographie des transports : application à Shanghai
Authors: Rodrigue J.P. , Comtois C.
Published: August 2023

The objective aims at verifying the hypothesis according to which the expert system technology in transport geography must first be seen as a set of complementary techniques, for it is only by underlying the degree to which a computer is required for solving problems, that the use of an expert system will be favored. The case of Shanghai demonstrates the complexity of such undertaking.

L'objectif consiste à vérifier l'hypothèse suivant laquelle la technologie du système expert en géographie des transports doit d'abord être vue comme un ensemble de technologies complémentaires car ce n'est qu'en soulignant le degré auquel l'assistance d'un ordinateur est requise dans la solution d'un problème, que l'utilisation d'un système expert sera favorisée. Le cas de Shanghai démontre la complexité des tâches à accomplir.
Analyse Coûts-Avantages et flexibilité des choix techniques en transport public
Authors: Denant-Boèmont Laurent
Published: August 2023

For ten years, the investment decisions in urban public transport have been occurring in an environment which faces an increasing uncertainty. The financial crisis, the appearance of new technologies and the apparent failure of economic appraisals have caused a real "decision crisis". In front of this rise of uncertainties, decision-makers are obviously displaying a preference for flexibility in the field of transport choices in urban areas. Indeed, they give greater importance to choices that provide the widest range of options for the future. Meanwhile, the irreversibility theories have experienced important developments, enabling economists to meet with the needs of decision-makers.The aim of this work is to suggest a methodology to compare levels of flexibility for alternative technical options in the well-known Cost-Benefit Analysis. The conception of a decision-taking model for transit should allow to estimate relative levels of risk, and especially to introduce the "irreversibility effect" as a part of socio-economic return. Simulations will be carried out, based on simple case studies in the field of public transport.

Depuis une dizaine d'années, les décisions d'investissement en transport collectif urbain sont prises dans un environnement caractérisé par des incertitudes croissantes. La crise financière, l'émergence de nouvelles technologies et la défiance envers les méthodes d'évaluation traditionnelles ont jeté les décideurs dans une véritable crise de la décision. Du fait de cette incertitude radicale, les décideurs révèlent alors une véritable préférence pour la flexibilité concernant les choix d'agglomération. En effet, ils accordent de plus en plus d'importance aux choix qui évitent de restreindre de façon trop importante les options pour les décisions futures, et qui procurent la plus grande marge de manœuvre possible. Parallèlement, depuis une vingtaine d'années, les théories de l'irréversibilité ont connu d'importants développements, qui permettent d'expliquer et d'intégrer les besoins des décideurs dans l'évaluation des projets.L'objectif de cette recherche est d'élaborer une méthodologie de comparaison des niveaux de flexibilité des variantes techniques dans une perspective d'Analyse Coûts-Avantages. La conception d'un modèle d'aide à la décision pour les transports publics permettra alors d'estimer les risques des projets ou variantes, et de faire de "l'effet-irréversibilité" une composante de la rentabilité collective des choix publics. Des simulations seront menées sur la base d'exemples fictifs de choix d'investissement dans le domaine étudié.
Optimal locations and distance prediction functions. Simulations based on an irregular lattice of points
Authors: Peeters Dominique , Thomas Isabelle
Published: August 2023

Distance predicting functions are commonly used for estimating road distances in transportation networks. The value of the parameters of these functions depend upon the studied empirical sample of places. In this paper, simulations are performed on a random lattice of 225 points in order to test how far the k-median outputs are sensitive to the way distances are estimated. The lp-distance is used with systematic changes in p (p varying from 0.4 to 9.0). Results lead to useful conclusions for further empirical use of the k-median: location-allocation results are little sensitive to changes in p, especially as far as " reasonable " empirical values of p are considered. The outputs of the simulations are systematically discussed.

Dans de nombreux modèles spatiaux, la distance réelle est estimée par une fonction de prédiction, telle la distance-lp. Les valeurs empiriques des paramètres associés à cette fonction dépendent du milieu géographique étudié. Cet article teste la sensibilité des résultats d’un modèle de localisation-affectation optimale (la k-médiane) à la manière d’estimer la distance, et plus particulièrement à la valeur du paramètre p dans la distance-lp. Un lattis théorique de 225 points générés aléatoirement est pris en compte ; 13 valeurs de p sont retenues (p varie de 0.4 à 9.0). Tous les outputs de la k-médiane sont discutés. Peu de différences sont observées dans les résultats opérationnels de la k-médiane, conduisant ainsi à des conclusions pratiques très intéressantes pour le planificateur : la manière d’estimer la distance sur un réseau de transport n’influence pas les choix décisionnels lorsque des valeurs " raisonnables " de p sont considérées (p Î [ 1.5 ; 2.2] ).
To analyse the mobility and urban relationshipsto reveal the spatial impacts of a major transport infrastructure
Authors: Bérion Pascal
Published: August 2023

The question of the impact of heavy transport infrastructures still remains a tremendous scientific enigma. They are few certainties about this problem at the moment, while a real political mystification of the effects of big amenities, known as "structuring infrastructures" develop outside the scientific community. But recent theoretical progress in geography and in regional economics, confirmed by extensive case studies, allows the investigation of new conceptual tracks to attempt to identify and understand the way these big infrastructures influence spatial structures and dynamics. Our research team gives greater importance to the study of the processes by which a transport infrastructure influences a spatial system. Among these, the one we call "process of usefulness and use" is essential. As one considers that the infrastructure provides new transport possibilities, we need to identify and then understand the way individuals and economics actors use them. This approach is applied to observe the economic effects of the A39 motorway (east of France).

La question des effets des grandes infrastructures de transport demeure encore une redoutable énigme scientifique. Malgré l'abondance des travaux engagés sur ce terrain, il apparaît que les certitudes sont encore minces alors même que se développe une véritable mystification politique des effets des grands équipements dits "structurants". Cependant, de récentes avancées théoriques, en géographie et en économie régionale, renforcées par de solides études de cas, permettent d'explorer de nouvelles pistes conceptuelles pour tenter d'identifier et de comprendre comment ces grandes infrastructures agissent sur les structures et dynamiques territoriales. Les recherches conduites dans cet esprit s’intéressent aux processus par lesquels l’infrastructure de transport intervient dans le fonctionnement d’un système territorial. Parmi ceux-ci le processus d’utilisation de l’équipement est essentiel. Il faut considérer que l’infrastructure permet de nouvelles possibilités de déplacements, aussi, il faut identifier comment les individus et les acteurs économiques les exploitent. Cette approche est concrètement mise en application dans le cadre de l’observatoire des effets économiques de l’autoroute A 39 (Est de la France).