Transit service quality analysis using cluster analysis and decision trees: a step forward to personalized marketing in public transportation

[EN] A transit service quality study based on cluster analysis was performed to extract detailed customer profiles sharing similar appraisals concerning the service. This approach made it possible to detect specific requirements and needs regarding the quality of service and to personalize the marketing strategy. Data from various customer satisfaction surveys conducted by the Transport Consortium of Granada (Spain) were analyzed to distinguish these groups; a decision tree methodology was used to identify the most important service quality attributes influencing passengers overall evaluations. Cluster analysis identified four groups of passengers. Comparisons using decision trees among the overall sample of all users and the different groups of passengers identified by cluster analysis led to the discovery of differences in the key attributes encompassed by perceived quality.The authors also acknowledge the Granada Consorcio de Transportes for making the data set available for this study. Griselda Lopez wishes to express her acknowledgement to the regional ministry of Economy, Innovation and Science of the regional government of Andalusia (Spain) for their scholarship to train teachers and researchers in Deficit Areas. Rocio de Ona wishes to express her acknowledgement to the regional ministry of Economy, Innovation and Science of the regional government of Andalusia (Spain) for the Excellence Research Project denominated "Q-METROBUS-Quality of service indicator for METROpolitan public BUS transport services'', co-funded with Feder.De Oña, J.; De Oña, R.; López-Maldonado, G. (2015). 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The effects of magnetic field, age, and intrinsic luminosity on Crab-like pulsar wind nebulae

We investigate the time-dependent behavior of Crab-like pulsar wind nebulae (PWNe) generating a set of models using 4 different initial spin-down luminosities ($L_0 =\{1,0.1,0.01,0.001\} \times L_{0, {\rm Crab}}$), 8 values of magnetic fraction ($\eta =$ 0.001, 0.01, 0.03, 0.1, 0.5, 0.9, 0.99, and 0.999, i.e., from fully particle dominated to fully magnetically dominated nebulae), and 3 distinctive ages: 940, 3000, and 9000 years. We find that the self-synchrotron Compton (SSC) contribution is irrelevant for $L_{SD}$=0.1, 1, and 10% of the Crab power, disregarding the age and the magnetic fraction. SSC only becomes relevant for highly energetic ($\sim 70$ of the Crab), particle dominated nebulae at low ages (of less than a few kyr), located in a FIR background with relatively low energy density. Since no pulsar other than Crab is known to have these features, these results clarify why the Crab Nebula, and only it, is SSC dominated. No young PWN would be detectable at TeV energies if the pulsar's spin-down power is 0.1% Crab or lower. For 1% of the Crab spin-down, only particle dominated nebulae can be detected by H.E.S.S.-like telescopes when young enough (with details depending on the precise injection and environmental parameters). Above 10% of the Crab's power, all PWNe are detectable by H.E.S.S.-like telescopes if they are particle dominated, no matter the age. The impact of the magnetic fraction on the final SED is varied and important, generating order of magnitude variations in the luminosity output for systems that are otherwise the same (equal $P$, $\dot P$, injection, and environment).Comment: Accepted for publication in MNRA

Is there room for highly magnetized pulsar wind nebulae among those non-detected at TeV?

We make a time-dependent characterization of pulsar wind nebulae (PWNe) surrounding some of the highest spin-down pulsars that have not yet been detected at TeV. Our aim is assessing their possible level of magnetization. We analyze the nebulae driven by J2022+3842 in G76.9+1.0, J0540-6919 in N158A (the Crab twin), J1400--6325 in G310.6--1.6, and J1124--5916 in G292.0+0.18, none of which have been found at TeV energies. For comparison we refer to published models of G54.1+0.3, the Crab nebula, and develop a model for N157B in the Large Magellanic Cloud (LMC). We conclude that further observations of N158A could lead to its detection at VHE. According to our model, a FIR energy density of 5 eV cm$^{-3}$ could already lead to a detection in H.E.S.S. (assuming no other IC target field) within 50 hours of exposure and just the CMB inverse Compton contribution would produce VHE photons at the CTA sensitivity. We also propose models for G76.9+1.0, G310.6--1.6 and G292.0+1.8 which suggest their TeV detection in a moderate exposure for the latter two with the current generation of Cherenkov telescopes. We analyze the possibility that these PWNe are highly magnetized, where the low number of particles explains the residual detection in X-rays and their lack of detection at TeV energies.Comment: Accepted for publication in MNRA

A proposal for cost-related and market-oriented train running charges

[EN] This paper examines some key aspects of a charging system for promoting railway transport, including charges reflecting a clear relationship with costs (transparency) and charges reflecting the quality of the infrastructure manager¿s service. Train running charges recover track-related costs and can help to develop a charging system that meets these requirements. To orient train running charges to the market, a method for processing track maintenance and renewal costs is proposed whereby the quality of the service provided by an infrastructure is measured according to its utility to the railway undertaking. To achieve transparency, a single indicator is used for cost planning and the subsequent levying of costs on railway undertakings. The paper includes an example of how proposed train running charges would be calculated according to data from 14 European countries. The example shows that short-distance trains generate the lowest maintenance and renewal costs, followed by long-distance trains and freight trains.This work was supported by the Spanish Ministerio de Fomento [grant number PT-2007-056-05CCPP].Calvo, F.; De Oña, J.; De Oña, R.; López-Maldonado, G.; Garach, L. (2014). A proposal for cost-related and market-oriented train running charges. Transportation Planning and Technology. 37(4):354-372. https://doi.org/10.1080/03081060.2014.897127S354372374Baumgartner, J. P. 2001. “Prices and Costs in the Railway Sector.” Laboratoire d'Intermodalité des Transports et de Planification. École Polytechnique Fédérale de Lausanne. Accessed February 4. http://litep.epfl.ch–2014Calvo, F., and J. de Oña. 2012a. “An Approach to Mark-Ups through Capacity Charges.”Proceedings of the ICE – Transport. Accessed February 4. http://www.icevirtuallibrary.com/content/article/10.1680/tran.11.00050.Calvo, F., & De Oña, J. (2012). Are rail charges connected to costs? Journal of Transport Geography, 22, 28-33. doi:10.1016/j.jtrangeo.2011.11.004Calvo, F., de Oña, J., López, G., Garach, L., & de Oña, R. (2013). Rail track costs management for efficient railway charges. Proceedings of the Institution of Civil Engineers - Transport, 166(6), 325-335. doi:10.1680/tran.11.00001Calvo, F., de Oña, J., & Nash, A. (2007). Proposed Infrastructure Pricing Methodology for Mixed-Use Rail Networks. Transportation Research Record: Journal of the Transportation Research Board, 1995(1), 9-16. doi:10.3141/1995-02CENIT, TIS PT, IWW, and HERRY. 2007. “RailCalc. Calculation of Charges for the Use of Rail Infrastructure.” Prepared for the European Commission Directorate General for Energy and Transport. Accessed February 4. http://ec.europa.eu/transport/rail/legislation/doc/railcalc_discussion_paper_final.pdf.ECMT (European Conference of Ministers of Transport). 2005. “Charges for the Use of Infrastructure in ECMT Railways.” Draft final report. ECMT/CS/CF(2005)1/REV1. Accessed February 4. http://lnweb90.worldbank.org/ECA/Transport.nsf/ECADocByUnid/2CF8BE276F63A37D85256FB20043A05D?Opendocument.EPFL (Ecole Polytechnique Féderale de Lausanne). 2003. “IMPROVERAIL: IMPROVEd Tools for RAILway Capacity and Access Management.” Accessed February 4. http://litep.epfl.ch.Network Rail. 2006. “Usage Costs – Assessment Methodology.” Draft for consultation. Accessed February 4. http://www.networkrail.co.uk/browse%20documents/regulatory%20documents/access%20charges%20reviews/consultations%20on%20future%20charging/variable%20track%20access%20charges/g-%20usage%20costs%20methodology%20sept%2006.pdf.Nyström, B., & Söderholm, P. (2010). Selection of maintenance actions using the analytic hierarchy process (AHP): decision-making in railway infrastructure. Structure and Infrastructure Engineering, 6(4), 467-479. doi:10.1080/15732470801990209ORR (Office of Rail Regulation). 2005. “Revision of Variable Usage and Electrification Asset Usage Charges: Final Report.” Accessed February 4. http://www.rail-reg.gov.uk/upload/pdf/bah_variable-usage-initial-report_jan05.pdf.Quinet, E. (2003). Short term adjustments in rail activity: the limited role of infrastructure charges. Transport Policy, 10(1), 73-79. doi:10.1016/s0967-070x(02)00047-1Thomas, J. 2002. “EU Task Force on Rail Infrastructure Charging: Summary Findings on Best Practice in Marginal Cost Pricing.” IMPRINT-EUROPE. Implementing Reform in Transport. Effective Use of Research on Pricing in Europe. A European Commission-funded Thematic Network (2001–2004). Accessed February 4. www.imprint-eu.org/public/Presentations/imprint3_Thomas.ppt.UIC (International Union of Railways). 2008. “Lasting Infrastructure Cost Benchmarking (LICB).” Summary Report. Accessed February 4. http://www.uic.org/spip.php?article582

Determination of the Night Sky Background around the Crab pulsar using its optical pulsation

The poor angular resolution of imaging gamma-ray telescopes is offset by the large reflector areas of next generation telescopes such as MAGIC (17~m diameter), which makes the study of optical emission associated with some gamma-ray sources feasible. Furthermore, the extremely fast time response of photomultipliers (PMs) makes them ideal detectors for fast (subsecond) optical transients and periodic sources like pulsars. The optical pulse of the Crab pulsar was detected with the HEGRA CT1 central pixel using a modified PM, similar to the future MAGIC camera PMs. The purpose of these periodic observations was to determine the light of the night sky (LONS) for the galactic anticenter Crab region.Our results are between 2.5 and 3 times larger than the previously measured LONS (outside the galactic plane), as expected since the Crab pulsar is in the galactic plane, which implies a slightly higher energy threshold for Crab observations, if the higher value of CT1 measured LONS rate for galactic sources is used.Comment: 19 pages, 6 figures, accepted by Astroparticle Physic

Analysis of traffic accident severity using Decision Rules via Decision Trees

[EN] A Decision Tree (DT) is a potential method for studying traffic accident severity. One of its main advantages is that Decision Rules can be extracted from its structure and used to identify safety problems and establish certain measures of performance. However, when it used only one DT, the rule extraction is limited to the structure of that DT and some important relationships between variables cannot be extracted. This paper presents a method for extracting rules from a DT more effectively. The method¿s effectiveness when applied to a particular traffic accidents dataset is shown. Specifically, our study focuses on traffic accident data from rural roads in Granada (Spain) from 2003 to 2009 (both included). The results show that we can obtain more than 70 relevant rules from our data using the new method, whereas with only one DT we would had extracted only 5 rules from the same dataset.Abellán, J.; López-Maldonado, G.; De Oña, J. (2013). Analysis of traffic accident severity using Decision Rules via Decision Trees. Expert Systems with Applications. 40(15):6047-6054. doi:10.1016/j.eswa.2013.05.027S60476054401

Development of safety performance functions for Spanish two-lane rural highways on flat terrain

[EN] Over decades safety performance functions (SPF) have been developed as a tool for traffic safety in order to estimate the number of crashes in a specific road section. Despite the steady progression of methodological innovations in the crash analysis field, many fundamental issues have not been completely addressed. For instance: Is it better to use parsimonious or fully specified models? How should the goodness-of-fit of the models be assessed? Is it better to use a general model for the entire sample or specific models based on sample stratifications? This paper investigates the above issues by means of several SPFs developed using negative binomial regression models for two-lane rural highways in Spain. The models were based on crash data gathered over a 5-year period, using a broad number of explanatory variables related to exposure, geometry, design consistency and roadside features. Results show that the principle of parsimony could be too restrictive and that it provided simplistic models. Most previous studies apply conventional measurements (i.e., R-2, BIC, AIC, etc.) to assess the goodness-of-fit of models. Seldom do studies apply cumulative residual (CURE) analysis as a tool for model evaluation. This paper shows that CURE plots are essential tools for calibrating SPF, while also providing information for possible sample stratification. Previous authors suggest that sample segmentation increases the model accuracy. The results presented here confirm that finding, and show that the number of significant variables in the final models increases with sample stratification. This paper point out that fully models based on sample segmentation and on CURE may provide more useful insights about traffic crashes than general parsimonious models when developing SPF. (C) 2016 Elsevier Ltd. All rights reserved.The authors would like to thank the ERDF of the European Union for financial support via project "Bases para un sistema experto que permita la identificacion probabilistica de Tramos de Concentracion de Crashes (TCA)" under the "Programa Operativo FEDER de Andalucia 2007-2013". We also thank the Public Works Agency and the Regional Ministry of Public Works and Housing of the Regional Government of Andalusia. Griselda Lopez wishes to express her acknowledgement of the regional ministry of Economy, Innovation and Science of the regional government of Andalusia (Spain) for their scholarship to train teachers and researchers in Deficit Areas.Garach, L.; De Oña, J.; López-Maldonado, G.; Baena-Ruiz, L. (2016). Development of safety performance functions for Spanish two-lane rural highways on flat terrain. Accident Analysis & Prevention. 95:250-265. https://doi.org/10.1016/j.aap.2016.07.021S2502659

Gamma rays from microquasars Cygnus X-1 and Cygnus X-3

Gamma-ray observations of microquasars at high and very-high energies can provide valuable information of the acceleration processes inside the jets, the jet-environment interaction and the disk-jet coupling. Two high-mass microquasars have been deeply studied to shed light on these aspects: Cygnus X-1 and Cygnus X-3. Both systems display the canonical hard and soft X-ray spectral states of black hole transients, where the radiation is dominated by non-thermal emission from the corona and jets and by thermal emission from the disk, respectively. Here, we report on the detection of Cygnus X-1 above 60 MeV using 7.5 yr of Pass8 Fermi-LAT data, correlated with the hard X-ray state. A hint of orbital flux modulation was also found, as the source is only detected in phases around the compact object superior conjunction. We conclude that the high-energy gamma-ray emission from Cygnus X-1 is most likely associated with jets and its detection allow us to constrain the production site. Moreover, we include in the discussion the final results of a MAGIC long-term campaign on Cygnus X-1 that reaches almost 100 hr of observations at different X-ray states. On the other hand, during summer 2016, Cygnus X-3 underwent a flaring activity period in radio and high-energy gamma rays, similar to the one that led to its detection in the high-energy regime in 2009. MAGIC performed comprehensive follow-up observations for a total of about 70 hr. We discuss our results in a multi-wavelength context.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea (arXiv:1708.05153