Often promoted by planning and transportation authorities as one of the principal ways to reduce the impact of mobility on transportation gas emissions, carpooling practices have increased over recent decades for daily commuting as well as long-distance travel. However, mainly due to the lack of data, little is known about the geography of these trips. On the one hand, the intensity of supply and demand may favor urban areas alongside common transportation systems. On the other hand, the scarcity of public transport in rural areas or small towns can support the growth of these shared mobilities. This article presents a geographical investigation of carpooling patterns in France and to overcome the lack of survey-data, it proposes an original method based on massive data collected from the Blablacar platform, national leader for this type of online services. After a review of the literature, the paper presents the main elements of the methodology implemented to collect and analyze the web data of carpooling. The analysis presents new findings that reveal the geographical features of car-sharing in France. The impact varies depending on the size of the towns, the presence of regional and inter-regional urban systems, and the tourism specialization of rural areas. The study also emphasizes the unique position of Paris and the pivotal role of intermediate towns.

Facing ecological transition issues, the carpooling is often promoted by planning and transportation authorities as one of the principal ways to reduce the impact of mobility on greenhouse gas emissions. If carpooling is for home-to-work trips, recent studies show the increase of this practice for long distance travels too. However, mainly due to the lack of data, little is known about the geography of these carpooling practices: do they relate major cities or do they serve rural places? The answer is not trivial. On the one hand, the intensity of supply and demand may favor urban areas. On the other hand, the absence of public transport in rural areas or small towns can support the growth of these shared mobilities. Depending on the answer, the policymaker might promote different policies. This article proposes a study of carpooling patterns in France by using data from the Blablacar platform that is the leader of carpooling platforms in France. Analysis bring several new results that highlight carpooling geographical differences and issues. On this base, we can imagine how to better adapt urban and regional transport and planning policies to develop carpooling in all territories.

Background Frequent car use contributes to health and environmental issues such as air pollution, climate change and obesity. Active and sustainable mobility (bike, walk, public transport, car sharing) may address these issues. Different strategies have been implemented in past research, involving hard levers, aimed at modifying the economical or geographical context (e.g., free public transport), and soft levers, aimed at modifying psychological processes (e.g., personalised transport advice). However, few studies have combined both hard and soft levers. In addition, few have used robust methodologies (e.g., randomised controlled trials), followed behavioural changes in the long-term, and been anchored in behaviour change theories. InterMob aims to address these limits by implementing a 24-month randomised controlled trial including hard and soft levers. The objectives of InterMob are to a) evaluate the effectiveness of an experimental arm versus an active controlled arm, and b) identify the processes of mobility change. Methods Regular car users living in Grenoble ( N = 300) will be recruited and randomised to one of the two arms. The experimental arm consists in a six-month intervention combining hard levers (free access to transport/bikes), and soft levers (e.g., personalised transport advice). The control arm consists in a six-month intervention aimed at raising awareness on air pollution and its health effects. Both arms will include eight evaluation weeks (spread out over 24 months) based on a GPS, an accelerometer, and a pollution sensor. Moreover, participants will complete mobility logbooks and surveys measuring psychological constructs, socio-economical, and socio-spatial characteristics. Discussion InterMob will assess the effectiveness of two interventions aimed at reducing car use within regular car users in the short-, mid- and long-term. Moreover, InterMob will allow to better understand the psychological processes of behaviour change, and the socio-economical and geographical conditions under which the intervention is efficient in reducing car use. Finally, the benefits of mobility change in terms of physical activity, quality of life, and exposure to pollution will be quantified. Trial registration ClinicalTrials.gov : NCT05096000 on 27/10/2021 (retrospectively registered).

VariaDe la carte diachronique à la trajectoire géohistorique : modélisation du changement paysager d'un cône torrentiel From diachronic map to geohistorical trajectory : modelizing the landscape change of an alluvial fan Del mapa diacrónico a la evolución geohistórica: modelización de la transformación paisajística de un cono de deyección

Images of sediment cores are often acquired to preserve primary color information, before such profiles are altered by subsequent sampling and destructive analyses. In many cases, however, no post-processing of these images is undertaken to extract information, despite the fact that image processing can be used to describe and measure structures within the sample. Improvements of RGB (Red/Green/Blue) cameras and image processing algorithms now enable acquisition of high-resolution, metrically calibrated pictures called ortho-images, which have great potential. The way to obtain such ortho-images is by processing several raw images. We propose a semi-automated method that uses metrically calibrated targets to create the ortho-image, using Agisoft Photoscan software and a Python script. The method was tested on sediment cores up to 1.5 m long. It was compared to an approach without markers, one that uses only image matching. The proposed method showed better resolution and less distortion (GSD: 59 µm, RMSE: 7–18 µm). Images acquired without calibrated targets can still be used, by manually positioning points that can then be metrically calibrated. This approach is very useful for smartphone images taken in the field. There are many potential applications for such images of sediment cores, for instance as metric stratigraphic logs to facilitate description of the profile by unit, to study and measure structures (e.g. laminae, instantaneous deposits), or use of image registration or data fusion to create spatial landmarks for non-destructive sensors or destructive laboratory analyses. High-resolution metrically calibrated RGB images of sediment cores are simple to acquire and can play an important role in paleoclimate and paleoenvironmental studies.

Cet article a pour objectif de présenter la méthodologie de diagnostic qualité et d’apurement des données, expérimentée à partir d’une enquête de mobilité individuelle (programme Mobi’Kids). Une première partie revient sur la démarche suivie et pointe l’enjeu de l’évaluation de la qualité de données hétérogènes issues d’une méthode mixte et longitudinale de collecte (suivis GPS, enquêtes, observations). Une deuxième partie établit un diagnostic qualité selon l’origine (GPS, algorithme, enquête) et la nature des erreurs (complétude, précision, cohérence). Ces typologies permettent, dans une troisième partie, de définir d’une chaîne de traitements reproductible visant à améliorer la qualité interne et externe des données.

This paper aims at proposing a data quality diagnosis and cleansing data methodology experimented on an individual mobility survey (Mobi'Kids program). The first section presents the theoretical approach to highlight the issue of a data quality diagnosis applied to heterogeneous data collected from mixed methods (GPS tracks, surveys, observations). Secondly, two typologies of major errors are discussed according to their origin (GPS, algorithm, survey) and their nature (completeness, accuracy, consistency). A processing chain is thirdly defined to improve both internal and external data quality in order to the perspective of a replicable methodology.

Cet article a pour objectif de presenter la methodologie de diagnostic qualite et d’apurement des donnees experimentee a partir d’une enquete de mobilite individuelle (programme MOBI’KIDS). Une premiere section revient sur la demarche suivie et pointe l’enjeu de l’evaluation de la qualite de donnees heterogenes issues d’une methode mixte et longitudinale de collecte (suivis GPS, enquetes, observations). Une deuxieme section etablit un diagnostic qualite selon l’origine (GPS, algorithme, enquete) et la nature des erreurs (completude, precision, coherence). Ces typologies permettent, dans une troisieme section, la definition d’une chaine de traitements reproductible visant a ameliorer la qualite interne et externe des donnees.

This article proposes a methodology to interpret old aerial photography applied to the geohistorical study of torrential landscapes. Indeed, as a primary source, images are historical proxies which foremost advantages are to locate and spatialise forms of changes. The aim of these researches is to produce a cartographical following of landscapes dynamics, through this type of archive. To achieve such a purpose, we choose a landscape sensitive to changes (torrential fan), considering landscape entities which equilibrium conditions responds to the socio-environmental context of a torrential northern alpine valley. In this exploratory aim of diachronic reconstruction, the photo-interpretative technics and remote sensing were associated. In this article, we explain the potentialities of an object-oriented approach using as an example a time series of areal missions taken by the National Geographic Institute of France (IGN-F©). The results of this method give a spatial and normalised comprehension over the fifty last years.

The past debris flow dynamics of the Ravin du Diable are analyzed by an integrative approach based on dendrogeomorphological methods coupling with diachronic orthophotography analysis. The aim is to reconstruct (i) both frequency and spatial extent of the recent debris flow activity, (ii) key debris flows on the cone dynamic and then (iii) the global torrential dynamics on a depositional forested cone in the French Prealps. Due to one of the most important landslide in Europe occurred in 1248, the Ravin du Diable is part of a very young and steep highly active catchment of 16 ha. Situated on the north face of the Mont Granier, part of Chartreuse Massif, this catchment is now well known for being an active debris flow corridor. Based on a dendrogeomorphological analysis, 315 growth disturbances from 189 trees (68% of resinous trees: Picea abies, Abies alba and 32% of broadleaved trees: Fraxinus excelsior, Alnus Incana) allowed a reconstitution of 14 events since 1968 including 7 unknowns debris flows in the historical archives and an estimation of 21 debris flows since 1915. Coupling with dendrogeomorphology, 13 orthophotographies since 1948 revealed channels activity, channels mobility, and different stages of the forest stand re-colonization. As a result obtained from this integrative approach, the spatial minimum extent of every major debris flows was mapped. Furthermore, 4 spatial morphological changing periods of the depositional cone dynamics were identified, resulting from debris flows intense activity.

On January 9, 2016 at 4:57, inhabitants of the municipality of Entremont-le-Vieux were awakened by the sound ofa large rock collapse detached from the Mont Granier (1933 m, Savoie, France), iconic mountain of the Chartreusemassif located between Chambery and Grenoble. Its north face, a 900-m-high natural geological cross section inUrgonian limestone, Hauterivian marls, Valanginian limestone and Berriasian marls, was affected in 1248 by ahuge collapse (500 million m3) that caused hundreds of fatalities.The SW pillar, shaped in the upper Urgonian limestone, climbed for the first time in 1964 and several times duringthe warm and dry autumn 2015, collapsed throughout its height (180 m) over a width of up to about 85 m witha volume certainly much higher than 100,000 m3. Blocks rolled down the western slope on about 700 m beforestopping in the forest. It is now notched over a hundred meter wide. No infrastructure was affected.The Granier has many predispositions to large instabilities. This is the western remaining part, largely fractured, ofa much eroded perched syncline whose inclination is oriented to the east. Fracturing and orientation of the stratacontributes to pre-cut limestone and marl. The Granier is also a major karstic area: the Granier plateau with itsmultilevel karst network (90 km of galleries explored) is a good model of polyphased karst network. The region isalso frequently affected by small earthquakes but seismicity does not appear to be a triggering factor. Conversely,the collapse has produced an M 2.2 earthquake. Besides rock fatigue related to what has just been mentioned anda vertical or overhanging topography, it is likely that heavy rains of days before the event and after a long periodof drought have unleashed the destabilization.The collapse is not comparable to the historical event of 1248, which had reshaped the entire northern side.However, its dimensions make the January 2016 event one of the major events of recent decades in the limestonewestern Alps. Events of this size are very rare in the currently available rockfall data series.There is now a significant residual risk of falling boulders while a large overhang just formed suggests probablecollapses in the short or medium term, with volumes exceeding 10,000 m3.