Assessment of the worthwhileness of efficient driving in railway systems with high-receptivity power supplies

Eco-driving is one of the most important strategies for significantly reducing the energy consumption of railways with low investments. It consists of designing a way of driving a train to fulfil a target running time, consuming the minimum amount of energy. Most eco-driving energy savings come from the substitution of some braking periods with coasting periods. Nowadays, modern trains can use regenerative braking to recover the kinetic energy during deceleration phases. Therefore, if the receptivity of the railway system to regenerate energy is high, a question arises: is it worth designing eco-driving speed profiles? This paper assesses the energy benefits that eco-driving can provide in different scenarios to answer this question. Eco-driving is obtained by means of a multi-objective particle swarm optimization algorithm, combined with a detailed train simulator, to obtain realistic results. Eco-driving speed profiles are compared with a standard driving that performs the same running time. Real data from Spanish high-speed lines have been used to analyze the results in two case studies. Stretches fed by 1 × 25 kV and 2 × 25 kV AC power supply systems have been considered, as they present high receptivity to regenerate energy. Furthermore, the variations of the two most important factors that affect the regenerative energy usage have been studied: train motors efficiency ratio and catenary resistance. Results indicate that the greater the catenary resistance, the more advantageous eco-driving is. Similarly, the lower the motor efficiency, the greater the energy savings provided by efficient driving. Despite the differences observed in energy savings, the main conclusion is that eco-driving always provides significant energy savings, even in the case of the most receptive power supply network. Therefore, this paper has demonstrated that efforts in improving regenerated energy usage must not neglect the role of eco-driving in railway efficiency

Fuzzy maximum capacity and occupancy time rate measurements in urban railway lines

Abstract Nowadays, railway transport capacity is an important bottleneck for many railway operators that face its ever-increasing demand. This poses a challenge to existing lines as operation under conditions close to saturation tends be unstable. Capacity in urban railway systems depends largely on dwell times at platforms, but capacity measures proposed in literature rarely include the uncertainty associated to these times. In this paper this uncertainty is modeled as fuzzy numbers and two new capacity measures are proposed: the Fuzzy Maximum Capacity and the Fuzzy Occupancy Time Rate. The proposed model makes use of a railway simulator that enables route compression to obtain the conflict-free compressed time of the section under study. Three practical capacity problems from the perspective of the railway traffic operator have been presented and solved. The new measures provide more information to the railway operator than the standard UIC method that does not include uncertainty regarding dwell times. Finally, the model has been applied to the section Gràcia-Sarrià, belonging to the Spanish railway operator FGC

Differences in the relative roles of environment, prey availability and human activity in the spatial distribution of two marine mesopredators living in highly exploited ecosystems

AimIdentifying the main factors affecting the spatial distribution of marine predators is essential in order to evaluate their distribution patterns, predict the potential impact of human activities on their populations and design accurate management actions. This information is also valuable from a more general management perspective, as marine predators are often considered indicators of habitat quality. In this context, we aimed to determine the degree to which environmental features, prey availability and human activities interact and influence spatial distribution of two marine mesopredator elasmobranchs, the small-spotted catshark (Scyliorhinus canicula) and the Mediterranean starry ray (Raja asterias), living in a highly human-exploited environment. LocationMediterranean Sea. MethodsWith information obtained from an extended experimental survey, we investigated the relative importance of environmental variables, prey availability and human activities on the spatial distribution of the abundance, biomass and occurrence rate of these marine mesopredators using deviance partitioning analyses. ResultsOur results revealed that environmental variables were the most important factors explaining the spatial distribution of Mediterranean starry ray, whereas small-spotted catshark distribution was also influenced by prey availability and human factors. From a management point of view, these findings suggest that Mediterranean starry ray could be a good candidate as an indicator species of demersal environmental quality. On the other hand, the distribution of the small-spotted catshark, which responds in an interactive and complex way to environment, prey availability and particular human activities, may be misleading as an environmental indicator. Main conclusionsThe spatial distribution of elasmobranchs in highly human-impacted marine areas can reflect the interactive and combined effects of multiple factors. To avoid misunderstandings, attention should be paid to statistical procedures allowing the separation of pure and joint contribution of the factors driving the observed spatial patterns

The relative roles of the environment, human activities and spatial factors in the spatial distribution of marine biodiversity in the Western Mediterranean Sea

Identifying the factors that affect the spatial distribution of marine biodiversity is a central issue to ecology. This knowledge is crucial to evaluate biodiversity patterns, to predict the impact of environmental change and anthropogenic activities, and to design accurate management programs. Here, we investigated the degree to which environmental features, human activities and spatial constraints interact and influence spatial gradients in marine biodiversity using the Western Mediterranean Sea as a model system. Our results revealed that a large fraction of the variability in biodiversity metrics of most marine groups analysed is accounted for by the joint effect of environment and human activities, environment and spatial variables or between all three groups of variables. In other words, major environmental variables and human activities have a collinear spatial structure, and thus an important part of the variation in biodiversity metrics can be attributed to these three groups of explanatory variables. Among pure effects, deviance partitioning results showed that the effect of environmental variables was more evident than the effect of human or spatial variables. The effect of single environmental and human variables considered in the analyses was different for different marine groups. This study contributes to the knowledge of the effects of ecological factors on the spatial distribution of marine biodiversity in the Mediterranean Sea, which is important in the development of more complex spatial analyses. Our results support the hypothesis that the joint effect of different predictor sets can be highly relevant in spatial patterns of biodiversity due to spatial collinearity. Thus, the simultaneous analysis of the relative effect of ecologically important predictor sets is important in preventing misinterpretations of the ecological mechanisms that explain spatial distribution of marine biodiversity

Accurate Measurements of Energy, Efficiency and Power Quality in the Electric Railway System

reserved16siThis paper describes a new EU co-funded project on metrology for smart energy management is electric railway systems (MyRailS). The project involves 7 national metrology institutes, 3 universities and 6 railway companies. Research focusses on the following topics: i) new calibration facilities for energy meters on-board installed, ii) power quality monitoring systems, iii) accurate estimation of the saved energy by the installation of new reversible substations (RSS) and iv) by the adoption of eco-driving strategies.mixedGiordano D.; Clarkson P.; Gamacho F.; Van Den Brom H.E.; Donadio L.; Fernandez-Cardador A.; Spalvieri C.; Gallo D.; Istrate D.; De Santiago Laporte A.; Mariscotti A.; Mester C.; Navarro N.; Porzio M.; Roscoe A.; Sira M.Giordano, D.; Clarkson, P.; Gamacho, F.; Van Den Brom, H. E.; Donadio, L.; Fernandez-Cardador, A.; Spalvieri, C.; Gallo, D.; Istrate, D.; De Santiago Laporte, A.; Mariscotti, A.; Mester, C.; Navarro, N.; Porzio, M.; Roscoe, A.; Sira, M