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101.
Andrés Gómez-Lobo 《运输评论》2013,33(3):297-315
AbstractThis paper provides a unifying framework to analyze whether a monopoly transit provider will under or over-supply frequency. To this end we couch the problem in term of Spence [(1975). Monopoly, quality and regulation. The Bell Journal of Economics, 6, 417–429] who analyzed the incentives to provide quality by a monopolist. We show that all of the results of a recent academic exchange discussing this topic are special cases of Spence [(1975). Monopoly, quality and regulation. The Bell Journal of Economics, 6, 417–429], albeit with an adjustment in order to take into account the cost structure of frequency provision in the case of public transport. In theory then, there are cases when a monopolist may offer optimal or above optimal levels of frequency without requiring subsidies. However, public transport is rarely provided by an unregulated monopolist. Rather, these services are usually provided either by an exclusive operator under regulated fares or by a group of competing operators, with or without fare regulation. We show that in the first case frequency will always be below the social optimal level. 相似文献
102.
Abstract This paper looks at estimated valuations of some service‐quality attributes in an airline choice context using stated preferences methods. The analysis is based on information obtained in the most important route connecting the Canary Islands with the Iberian Peninsula: Gran Canaria–Madrid, and tries to contribute to the body of knowledge in this area, given the relatively few studies of the monetary valuations of air travel regarding level‐of‐service attributes. A feature of this analysis is the examination of variations in values according to different characteristics of the service, such as price, penalties for changes in the ticket, legroom, food, etc.; the currently experienced level of the attribute, and various socio‐economic factors that affect the characteristics of the trip and passengers. In addition, the important issue of added value regarding different attributes is addressed, obtaining the willingness‐to‐pay for different improvements of service quality. A further analysis is made about how taste heterogeneity (market segments) affects these values. Results from the stated preference experiment and the market value of some comparable service are also compared. Finally, the paper brings together evidence from other studies and compares them with the findings obtained herein. 相似文献
103.
Miguel Ángel López-Navarro Miguel Ángel Moliner Rosa María Rodríguez Javier Sánchez 《运输评论》2013,33(4):425-444
Short sea shipping (SSS) is called to play a key role in ensuring sustainable mobility in the European context. In the past years several studies tried to define the SSS requirements and also to identify the SSS lines that were economically viable. However, no studies approach the profile of their users—the road transport firms—and the organizational patterns adopted by them, in order to gain a better understanding of this transport modality. This research, on the basis of a sample of 81 international road transport firms that use SSS between Spain and Italy, analyses the profile of these firms and certain elements inherent to their relationship with the shipping firms, according to the two modalities of organizing their SSS transport operations: accompanied versus unaccompanied. 相似文献
104.
105.
Although the study of the role of the social context in travel behavior and activity patterns has recently gained attention, the empirical evidence supporting the relationship between social networks and the temporal and spatial characteristics of social activities is still limited. With this motivation, this paper studies the link between “longer term” (social networks) and “shorter term” (social activities) social decisions, by exploring the intertwined relationship between the individuals’ personal networks attributes, and the spatiotemporal characteristics of their daily social activities. The paper contributes to the literature by adding two key aspects to the study of the role of social networks on travel behavior: the social networks’ structure, and the spatiality of all individuals participating on the social activities. Based on data which link people’s personal networks and time use, and using a structural equation modeling approach, the paper studies the influence of individual and interactional attributes on the duration, distance, and number of people involved in social daily activities. The results show that aspects such as tie social closeness, gender and age similarity, and network density, help to understand social activity duration and distance, complementing traditional socio-demographic aspects such as income, occupation, and accessibility to services. In this way, socio-demographic attributes are not enough to explain the spatiotemporal dimension of daily activities which makes necessary to include variables related to the social context to explain with a higher level of accuracy both the duration and distance traveled to the activity. 相似文献
106.
Abstract This paper concerns the newspaper distribution problem. It addresses the transportation of newspapers from printing plant to newsagents with distribution vehicles under various particular constraints. The objective is to minimize the distance traveled by the vehicles and/or the number of vehicles. In this study, the routes for vehicles of a leading newspaper distributor company in the Turkish press sector are examined. The problem is defined as determining optimal delivery routes for a fleet of homogeneous vehicles, starting and ending at the printing plant that is required to serve a number of geographically dispersed newsagents with known demands under capacity and time constraints, while minimizing the total distribution cost. An integar linear programming model is proposed as a solution using Cplex. Computational results demonstrate that the proposed model is fast and able to find optimal solutions for problem scenarios with up to 55 newsagents within reasonable computing times. It was found that the proposed model reduced the delivery cost by 21% on average when compared to the current manual method. The results show that this model is adequate for medium-sized distribution problems. 相似文献
107.
Vassilis Kitidis Louise Tizzard Günther Uher Alan Judd Rob C. Upstill-Goddard Ian M. Head Neil D. Gray Gillian Taylor Ruth Durn Raquel Diez Jorge Iglesias Soledad García-Gil 《Journal of Marine Systems》2007,66(1-4):258
Methane (CH4) concentrations were measured in the water column, in sediment porewaters, and in atmospheric air, in the Ría de Vigo, NW Spain, during both the onset (April 2003) and at the end of (September 2004) seasonal upwelling. In addition, CH4 concentration and stable isotopic signatures (δ13CH4) were measured in porewaters, and sediment methanogenesis and aerobic oxidation of CH4 were determined in sediment incubations. Surface water column CH4 (2 m depth) was in the range 3–180 nmol l− 1 (110–8500% saturation) and followed a generally landward increase but with localised maxima in both the inner and middle Ría. These maxima were consistent with CH4 inputs from underlying porewaters in which CH4 concentrations were up to 3 orders of magnitude higher (maximum 350 μmol l− 1). Surface water CH4 concentrations were approximately three times higher in September than in April, consistent with a significant benthic CH4 flux driven by enhanced sediment methanogenesis following the summer productivity maximum. CH4 and δ13CH4 in sediment porewaters and in incubated sediment slurries (20 °C) revealed significant sediment CH4 oxidation, with an apparent isotopic fractionation factor (rc) of 1.004. Using turbulent diffusion models of air–sea exchange we estimate an annual emission of atmospheric CH4 from the Ría de Vigo of 18–44 × 106 g (1.1–2.7 × 106 mol). This estimate is approximately 1–2 orders of magnitude lower than a previous estimate based on a bubble transport model. 相似文献
108.
建成环境对步行和自行车出行的影响--以波哥大为例 总被引:1,自引:0,他引:1
Robert Cervero Olga L. Sarmiento Enrique Jacoby Luis Fernando Gomez Andrea Neiman 耿雪 《城市交通》2016,(5):83-96
哥伦比亚波哥大以可持续的城市交通系统闻名,包括其密集的自行车道网络以及Ciclovía系统——为骑车者和行人预留的道路空间,可在星期日和节假日休闲出行使用。探讨此类设施以及建成环境的其他属性——城市密度、混合用地、可达性以及与公共交通车站的距离——如何影响步行和自行车出行行为以及Ciclovía的使用。结果表明,道路设施设计要素例如道路密度、连通性、与Ciclovía车道的距离,与体力活动相关;而建成环境的其他属性如密度和用地混合程度,对体力活动影响甚微。这可能是由于波哥大建成区的大部分街区均在非机动交通出行占绝对优势的时期演变发展——紧凑、用地混合、交通可达性水平相似。由此可见,影响非机动交通出行的因素是设施设计而非一般的街区用地属性。 相似文献
109.
This paper reviews and compares the performance of two dynamic transportation models – METROPOLIS and SILVESTER – which are used to predict the impacts of congestion charging for Stockholm. Both are mesoscopic dynamic models treating accumulation and dissipation of traffic queues, route choice, modal split and departure time choice. The models are calibrated independently for the baseline situation without charges and applied to forecast the effects of congestion charging. The results obtained from the two models are mutually compared and validated against the actual outcome of the Stockholm congestion charging scheme. Both models successfully predict the outcomes of the congestion charging trial at both aggregate and disaggregate levels. Results of welfare analysis, however, differ substantially due to differences in model specification. 相似文献
110.
王宇 《西安交通大学学报(英文版)》1995,(2)
ENHANCEDNITRICOXIDE(NO)-MEDIATEDVASODILATIONINLOWPOTASSIUMMEDIUMwagnYu;OS.Steinsland,SH.Nelson,AE.Feerick,WE.Johnstonn(Depart?.. 相似文献