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排序方式: 共有185条查询结果,搜索用时 15 毫秒
71.
Björn Hassler 《Maritime Policy and Management》2013,40(5):489-503
Despite significant efforts to improve environmental safety in marine oil transportation, the risk of a major accident with devastating oil spills has most likely increased. Building on the regime analytical approach where it is assumed that international collaboration may benefit participating countries, it is argued that bilateral and sub-regional initiatives may increase maritime safety significantly, compared to exclusive reliance on universal conventions. A distinction is made between on the one hand investments in safety-increasing infrastructure and local capacity building and on the other, vessel design, on-board installations and crew qualifications. It is suggested that bilateral and sub-regional initiatives are more likely to be taken on the former kind of objects, targeting issues, such as modernization of port facilities, monitoring support, assistance in emergency capacity building and designation of ports of refuge, because the interaction between the involved countries are comparably stable in the cases. Actual efforts to improve safety seem to follow the logic of separation between these two types of safety-increasing measures. It is concluded that similar drivers of bilateral and sub-regional initiatives targeting specific aspects of marine safety and contributing to overall collective benefits from improved environmental protection probably exist also in other regions than the Baltic Sea. 相似文献
72.
Abstract The negative impacts of transport are in general associated with costs. These costs are usually denoted as ‘external costs’ or ‘externalities’. This paper presents a tool for calculating external costs for freight transport together with its application to a number of case studies. The categories considered include: air pollution, greenhouse gases, noise, accidents and congestion. Results are presented for a number of different transport alternatives as total costs and divided into categories. The uncertainties in the results are discussed. The assessment of these costs is essential for predicting future transport costs. 相似文献
73.
As congestion pricing has moved from theoretical ideas in the literature to real-world implementation, the need for decision support when designing pricing schemes has become evident. This paper deals with the problem of finding optimal toll levels and locations in a road traffic network and presents a case study of Stockholm. The optimisation problem of finding optimal toll levels, given a predetermined cordon, and the problem of finding both optimal toll locations and levels are presented, and previously developed heuristics are used for solving these problems. For the Stockholm case study, the possible welfare gains of optimising toll levels in the current cordon and optimising both toll locations and their corresponding toll levels are evaluated. It is shown that by tuning the toll levels in the current congestion pricing cordon used in Stockholm, the welfare gain can be increased significantly, and furthermore improved by allowing a toll on a major bypass highway. It is also shown that, by optimising both toll locations and levels, a congestion pricing scheme with welfare gain close to what can be achieved by marginal social cost pricing can be designed with tolls being located on only a quarter of the tollable links. 相似文献
74.
Karl Sörenson 《WMU Journal of Maritime Affairs》2018,17(1):31-48
This article considers whether the Somali pirates were deterred by the naval task forces between the years 2009 and 2013. By disaggregating data and using previously unpublished records regarding the naval operations, two areas of operations are identified as potential periods of deterrence. The article uses a model of asymmetric deterrence to study the outcomes and equilibria of the navy-pirate interaction. It is found that the naval operations eventually did deter the Somali pirates in the Gulf of Aden, but that this objective was not met in the Somali Basin. It is concluded that the operational focus on the Gulf of Aden coupled with the fact that the area is relatively smaller than the Somali Basin enabled the naval credibility, thus effectively denying the pirates access to the sea. Conversely, limited attention by the naval units and the long Somali southern coast with its open waters impeded naval control in the Somali Basin. In connection to these findings some conclusions regarding naval deterrence are discussed. 相似文献
75.
The study presented in this paper aims at investigating what safety measures that can be taken to improve the operational safety during icebreaker operations in the Baltic Sea. During icebreaker operations, the icebreaker and the assisted vessel operate in close proximity to each other, a distance which can be even smaller if weather and ice conditions are severe. This poses a severe threat to the operation, since the extremely short distance between the vessels leaves no room for error. The results, which are based on data collected through individual interviews and questionnaires, indicate several possible improvements. Firstly, on a regulatory level, the introduction of an ice navigation certificate for deck officers would set a minimal level of formal competency. Secondly, on a knowledge level, more ice navigation training and better language skills work in favour for the safety. Thirdly, on a technical level, having an electronic chart with target tracking capability increases the efficiency and safety of the passage through ice. In addition to these results, this study shows a need to further research the communication and language situation during icebreaker operations. 相似文献
76.
A package of large-scale investments in the transportation infrastructure in the Stockholm metropolitan region is currently being proposed. It contains new investments in the railway and subway systems as well as new links in the road system. This paper deals with the issue of appraising this kind of investment program. One major problem is the lack of a unique standard method, and it is argued that several tools should be used in a practical evaluation of large-scale investments in the transportation system.Four different approaches are presented and related to each other. First, one study uses a network-based mode-split/assignment model with a fixed trip matrix. The second study is complementary, as its aim is to also trace the impacts on the spatial distribution of population and jobs by applying an integrated transportation and land use model. Third, the long-run effects of the investments on regional economic growth are discussed within the framework of regional production functions. Fourth, an alternative approach is used, in which benefits from the investments are assessed through their estimated influence on aggregate land values.Abbreviations RA
Reference Alternative
- IP
Investment Proposal
- IMREL
Integrated Model of Residential and Employment Location
- RPFM
Regional Production Function Model
An earlier version of this paper was presented at the 31th European Congress of the Regional Science Association, Lisbon, August 1991. 相似文献
77.
Claudio Benini Marco Gadola Daniel Chindamo Stefano Uberti Felipe P. Marchesin Roberto S. Barbosa 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2017,55(3):338-350
This work analyses the effect of friction in suspension components on a race car vertical dynamics. It is a matter of fact that race cars aim at maximising their performance, focusing the attention mostly on aerodynamics and suspension tuning: suspension vertical and rolling stiffness and damping are parameters to be taken into account for an optimal setup. Furthermore, friction in suspension components must not be ignored. After a test session carried out with a F4 on a Four Poster rig, friction was detected on the front suspension. The real data gathered allow the validation of an analytical model with friction, confirming that its influence is relevant for low frequency values closed to the car pitch natural frequency. Finally, some setup proposals are presented to describe what should be done on actual race cars in order to correct vehicle behaviour when friction occurs. 相似文献
78.
Lehtonen Esko Wörle Johanna Malin Fanny Metz Barbara Innamaa Satu 《Transportation》2022,49(5):1295-1314
Transportation - Automated vehicles (AVs) are expected to change personal mobility in the near future. Most studies on the mobility impacts of AVs focus on fully automated (SAE L5) vehicles, but... 相似文献
79.
80.
A meta-analysis of DEA and SFA studies of the technical efficiency of seaports: A comparison of fixed and random-effects regression models 总被引:1,自引:0,他引:1
James Odeck Svein Bråthen 《Transportation Research Part A: Policy and Practice》2012,46(10):1574-1585
This paper presents a meta-analysis of variations in seaports’ Mean Technical Efficiency (MTE) scores based on 40 studies published in refereed academic journals. We link the variation in estimated MTE scores to differences in the following factors: the frontier methodology used, which essentially are the Data Envelopment Analysis (DEA) and the Stochastic Frontier Analysis (SFA); regions where seaports are situated; type of data used; number of observations; and the total number of variables used. Furthermore, we compare fixed-effects against a random-effects regression model where the latter assumes that the individual study specific characteristics matter while the former assumes that there is one general tendency across all studies. We present several findings based on the data: (1) the random-effects model outperforms the fixed effects model in explaining the variations in MTEs, (2) recently published studies have lower MTE scores as compared with earlier published studies, (3) studies that used nonparametric DEA models depict higher MTE scores as compared with those that used SFA models, (4) panel data studies have lower TE scores as compared with cross-sectional data, and (5) studies using European seaport data produce lower MTE scores when compared with the rest of the world. Finally, our results contradict some previous meta-analysis studies of TE scores. We encourage the use of random-effects models in meta-analysis studies because they account for individual study specific effects. 相似文献