Freeway lane-changing: some empirical findings

Lane changing activity is thought to play an important role in the capacity degradation of congested freeways. However, proofs of this negative impact are scarce due to the difficulties in obtaining suitable data. In this paper, the lane changing activity in the B-23 freeway accessing the city of Barcelona is analyzed. Lane changes (LC) were video recorded in six different stretches from where loop detector measurements were also available. The obtained database allowed finding a consistent relationship between LC activity and congestion. LC peaks in all analyzed sections when they become congested. This is particularly intense at the traffic breakdown, between congested and free flowing conditions. As an example, it is observed that LC activity peaks just downstream of a fixed bottleneck where free-flowing conditions are recovered. In addition, data show that the larger the lane changing rates, the smaller the maximum observable flows, supporting the hypothesis that LC is a key contributor to a capacity drop. In spite of all these findings, this research highlights the difficulty in obtaining a suitable database to definitively answer most of the research questions regarding freeway lane-changing. The spatial coverage of measurements is one of the major drawbacks. To this end, a careful planning of the data collection is necessary in order to obtain meaningful conclusions.Postprint (published version

Measuring traffic flow and lane changing from semi-automatic video processing

Comprehensive databases are needed in order to extend our knowledge on the behavior of vehicular traffic. Nevertheless data coming from common traffic detectors is incomplete. Detectors only provide vehicle count, detector occupancy and speed at discrete locations. To enrich these databases additional measurements from other data sources, like video recordings, are used. Extracting data from videos by actually watching the entire length of the recordings and manually counting is extremely time-consuming. The alternative is to set up an automatic video detection system. This is also costly in terms of money and time, and generally does not pay off for sporadic usage on a pilot test. An adaptation of the semi-automatic video processing methodology proposed by Patire (2010) is presented here. It makes possible to count flow and lane changes 90% faster than actually counting them by looking at the video. The method consists in selecting some specific lined pixels in the video, and converting them into a set of space – time images. The manual time is only spent in counting from these images. The method is adaptive, in the sense that the counting is always done at the maximum speed, not constrained by the video playback speed. This allows going faster when there are a few counts and slower when a lot of counts happen. This methodology has been used for measuring off-ramp flows and lane changing at several locations in the B-23 freeway (Soriguera & Sala, 2014). Results show that, as long as the video recordings fulfill some minimum requirements in framing and quality, the method is easy to use, fast and reliable. This method is intended for research purposes, when some hours of video recording have to be analyzed, not for long term use in a Traffic Management Center.Postprint (published version

Extracting weather features from outdoor scene images using convolutional neural networks

En aquesta tesi construïm un nou conjunt de dades amb imatges extretes de webcams situades arreu del món utilitzant EarthCam, una web pública on tenen diverses càmeres en directe que mostren escenes exteriors i on qualsevol usuari pot realitzar una captura de pantalla en qualsevol moment i es publica a la web, ho anomenen Saló de la Fama. Aleshores associem les imatges amb les seves condicions meteorològiques, obtingudes a través de l'API d'OpenWeather, com la descripció de la condició meteorològica principal i la temperatura. També desenvolupem diferents xarxes neuronals convolucionals per predir la condició meteorològica per una imatge i proposem noves arquitectures per predir la temperatura d'imatges d'escenes en les quals el model no ha estat entrenat.En esta tesis construimos un nuevo conjunto de datos con imágenes extraídas de webcams situadas alrededor del mundo usando EarthCam, una web pública donde tienen múltiples cámaras en directo que muestran escenas exteriores y donde cualquier usuario puede realizar una captura de pantalla en cualquier momento y se publica en la web, lo llaman Salón de la Fama. Entonces asociamos las imágenes con sus condiciones meteorológicas, obtenidas mediante la API de OpenWeather, como la descripción de la condición meteorológica principal y su temperatura. También desarrollamos diferentes redes neuronales convolucionales para predecir la condición meteorológica principal de una imagen y proponemos nuevas arquitecturas para predecir la temperatura de imágenes de escenas donde el modelo no ha sido entrenado.In this thesis we construct a new dataset with images extracted from webcams around the world using EarthCam, a public website where they have multiple live cameras showing outdoor scenes and any user can take a screenshot of the camera at any time and it becomes publicly available, they call this the Hall of Fame. We associate the images with their weather conditions, obtained via the OpenWeather API, such as the main weather description and the temperature. We also develop convolutional neural networks to predict a weather condition for an image and we propose some new model architectures for being able to predict the temperature from images from places the model has not been trained on.Outgoin

A simulation model for public bike-sharing systems

Urban areas are in need of efficient and sustainable mobility services. Public bicycle sharing systems stand out as a promising alternative and many cities have invested in their deployment. This has led to a continuous and fast implementation of these systems around the world, while at the same time, research works devoted to understand the system dynamics and deriving optimal designs are being developed. In spite of this, many promoting agencies have faced the impossibility of evaluating a system design in advance, increasing the uncertainty on its performance and the risks of failure. This paper describes the development of an agent-based simulation model to emulate a bike-sharing system. The goal is to obtain a tool to evaluate and compare different alternatives for the system design before their implementation. This tool will support the decision-making process in all the stages of implementation, from the strategical planning to the daily operation. The main behavioral patterns and schemes for all agents involved are designed and implemented into a Matlab programming code. The model is validated against real data compiled from the Barcelona’s Bicing system showing good accuracy.Postprint (published version

El proyecto colonizador de Raïmat: la formación de un viñedo (1914-1948)

Raïmat es el resultado de un ambicioso proyecto colonizador, que después de los primeros cincuenta años de actividad, se centró finalmente en la viticultura para dar lugar a la mayor explotación de Europa. En este artículo se mostrará la complejidad de este proceso colonizador, que se caracteriza por la voluntad de implantación en un paraje antes deshabitado y por la capacidad de superación de las grandes dificultades que oponía a la agricultura esta finca de 3.000 Ha. Como contrapunto, se señalará el modo en que se supieron utilizar sus ventajas de localización: las comunicaciones y el agua. La cuestión fundamental es explicar cómo la viticultura se ha ido implantando allí paulatinamente, ganando terreno a la silvicuiltura y al resto de cultivos agrícolas, a partir de los datos inéditos de la propia empresa

Effects of low speed limits on freeway traffic flow

Recent years have seen a renewed interest in Variable Speed Limit (VSL) strategies. New opportunities for VSL as a freeway metering mechanism or a homogenization scheme to reduce speed differences and lane changing maneuvers are being explored. This paper examines both the macroscopic and microscopic effects of different speed limits on a traffic stream, especially when adopting low speed limits. To that end, data from a VSL experiment carried out on a freeway in Spain are used. Data include vehicle counts, speeds and occupancy per lane, as well as lane changing rates for three days, each with a different fixed speed limit (80 km/h, 60 km/h, and 40km/h). Results reveal some of the mechanisms through which VSL affects traffic performance, specifically the flow and speed distribution across lanes, as well as the ensuing lane changing maneuvers. It is confirmed that the lower the speed limit, the higher the occupancy to achieve a given flow. This result has been observed even for relatively high flows and low speed limits. For instance, a stable flow of 1942 veh/h/lane has been measured with the 40 km/h speed limit in force. The corresponding occupancy was 33%, doubling the typical occupancy for this flow in the absence of speed limits. This means that VSL strategies aiming to restrict the mainline flow on a freeway by using low speed limits will need to be applied carefully, avoiding conditions as the ones presented here, where speed limits have a reduced ability to limit flows. On the other hand, VSL strategies trying to get the most from the increased vehicle storage capacity of freeways under low speed limits might be rather promising. Additionally, results show that lower speed limits increase the speed differences across lanes for moderate demands. This, in turn, also increases the lane changing rate. This means that VSL strategies aiming to homogenize traffic and reduce lane changing activity might not be successful when adopting such low speed limits. In contrast, lower speed limits widen the range of flows under uniform lane flow distributions, so that, even for moderate to low demands, the under-utilization of any lane is avoided. These findings are useful for the development of better traffic models that are able to emulate these effects. Moreover, they are crucial for the implementation and assessment of VSL strategies and other traffic control algorithms.Peer ReviewedPostprint (published version

Travel time estimation using toll collection data

Transportation System Management (TSM) permits optimizing the current available road network. Travel time and its reliability are key factors in road management systems, as they are good indicators of the level of service in any road link, and perhaps the most important parameter for measuring congestion. This paper presents a new approach for direct travel time measurement using existing toll infrastructure. An efficient and simple algorithm has been developed and implemented in the toll highways in Catalonia, around Barcelona, Spain.Peer Reviewe

Estimación del tiempo de viaje en autopistas

El tiempo de viaje (TV) para conducir por carretera es la información más apreciada de tráfico. La medición del TV en tiempo real es también un indicador perfecto del nivel de servicio en una carretera, y por lo tanto es una medida útil para los gestores de tráfico para mejorar las operaciones en la red. Entonces, la medición exacta del TV es uno de los factores clave en los sistemas de gestión del tráfico. Por otro lado, el desarrollo de nuevos sistemas de control del tráfico y el creciente interés de los operadores de las carreteras e investigadores en la obtención de mediciones fiables del TV ha llevado al desarrollo de múltiples fuentes de datos de TV y algoritmos de estimación. Esta situación proporciona un contexto perfecto para la aplicación de metodologías de fusión de datos para obtener la máxima precisión de la combinación de los datos disponibles