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41.

The British Bus industry has undergone considerable transformation since privatization. Five major operators have emerged to dominate the market, a position almost exclusively attained through acquisition. This paper reviews the economies of scale argument commonly cited for this change and gives an overview of the acquisition process. It questions whether this argument gives a complete explanation for this industry development. For 58 individual companies, the level of technical efficiency attributable to firms operating at or near the optimum level of output is examined over 5 years to determine if mergers in practice have resulted in scale economies. Technical efficiency is estimated using data envelopment analysis, under assumptions of constant and variable returns to scale. Efficiency scores are then regressed on a time trend and a merger dummy to test whether acquired firms' efficiency has significantly improved above the average. It was found that over the period, efficiency had improved. This improvement, however, cannot be wholly attributed to the achievement of economies of scale. More specifically, there has been an improvement in the internal efficiency of acquired firms and some scale economies within group companies, the latter of which may have resulted from the eradication of competition.  相似文献   
42.

This paper reviews methods that have and can be used to forecast the effect of changes in accessibility to the rail network on the demand for inter-urban rail travel and of available evidence on rail accessibility elasticities. It reveals that relatively little research has been conducted in this area and that the forecasting procedures that could be used imply large variation in accessibility elasticities, which has not been empirically justified. Fresh empirical evidence on two related matters is reported. First, the neglected area of choice set composition is examined and the extent to which rail is considered to be a realistic alternative for inter-urban journeys and the contribution that accessibility to the rail network makes to this are analysed. Second, rail trip rate models are presented that not only contain estimates of accessibility elasticities and of the effects of a range of socio-economic variables on the demand for rail travel, but also that allow tests of the accessibility elasticity variation implied by many forecasting procedures to be conducted. It is found that this elasticity variation is not empirically supported. It is concluded that there is only limited scope for increasing rail demand through improvements in rail network accessibility.  相似文献   
43.
We investigate a role for vertical migration in stratified coastal water, where the swimming speed is generally significantly less than the typical turbulent fluctuations in a tidally-mixed bottom layer. In our modelling approach we use a k- turbulence model to describe the physical forcing, a Lagrangian random walk model to describe the vertical displacement of individual cells in response to turbulence and due to cell motility, and a phytoplankton growth model to direct the swimming behaviour of the phytoplankton according to their light and nutrient requirements. The model results show how the cells form a stable subsurface chlorophyll maximum (SCM) at the base of the thermocline where episodic tidal turbulence causes erosion of part of the SCM biomass into the bottom mixed layer (BML). We then focus on the question of whether an ability to swim (weakly, compared to typical bottom layer turbulent intensities) provides any advantage by allowing return to the SCM. Our results show that tidal turbulence in the BML helps both motile and neutrally-buoyant cells by periodically pushing them into the base of the thermocline. Motile cells then have the advantage that they can swim further into the thermocline towards higher light which also reduces the likelihood of being re-mixed back into the BML.  相似文献   
44.
This paper stresses the lack of attention paid to the geographical definitions of cities in LUTI models as one key detrimental aspect to transferring and generalising LUTI results. First, the argumentation develops from a meta-analysis of peer-reviewed publications about LUTI applications in European cities. We show that most authors do not assess findings against potential geographical biases. Second, theoretical simulations are conducted with UrbanSim applied to a synthetic urban area. By varying the geographical limits of the system and population endowments, our simulations confirm that the absence of control on city delineation weakens the results. Finally, the paper suggests methodological guidelines to improve the comparability of LUTI applications and push forward their theoretical agenda.  相似文献   
45.
ABSTRACT

This paper develops cost models for urban transport infrastructure options in situations where motorcycles and various forms of taxis are important modes of transport. The total social costs (TSCs) of conventional bus, Bus Rapid Transit (BRT), Monorail, Metro (Elevated Rail), car, motorcycle, Taxi and Uber are calculated for an urban corridor covering operator, user and external costs. Based on the parameters for a 7?km corridor in Hanoi, Vietnam, the results show the lowest average social cost (ASC) transport modes for different ranges of demand. Motorcycle might be the best option at low demand levels while conventional bus has advantages with low-medium demand. At medium demand levels, bus-based technologies and Monorail are competitive options while Metro, with a higher person capacity, is the best alternative at the highest demand levels. Compared to other modes, the ASCs of car and Taxi/Uber are greater because of high capital cost (related to vehicles) per passenger and low occupancy. Transport planners and decision makers in low and middle income countries (LMICs) can draw on the findings of this study. However, various limitations are identified and additional research is suggested.  相似文献   
46.
This paper analyzes the transportation and land-use preference and actual neighborhood choices of a sample of 1,455 residents of metro Atlanta. We develop a stated-preference scale on which desires for neighborhood type are gauged, from preferences for low-density, auto-oriented environments to desires for compact, walkable, and transit-oriented neighborhoods. This scale is then related to desires for change in one’s own neighborhood characteristics after a hypothetical move. If all neighborhood preferences were equally likely to be satisfied, then neighborhood preferences would not be correlated with a desire for change. By contrast, in the current study, stronger preferences for a more walkable environment are associated with greater desire for change in one’s neighborhood characteristics. This suggests an undersupply of compact, walkable, and transit-friendly neighborhood types relative to current demand.
Lawrence D. Frank (Corresponding author)Email:
  相似文献   
47.
Most unsignalised intersection capacity calculation procedures are based on gap acceptance models. Accuracy of critical gap estimation affects accuracy of capacity and delay estimation. Several methods have been published to estimate drivers' sample mean critical gap, the Maximum Likelihood Estimation (MLE) technique regarded as the most accurate. This study assesses three novel methods; Average Central Gap (ACG) method, Strength Weighted Central Gap method (SWCG), and Mode Central Gap method (MCG), against MLE for their fidelity in rendering true sample mean critical gaps. A Monte Carlo event based simulation model was used to draw the maximum rejected gap and accepted gap for each of a sample of 300 drivers across 32 simulation runs. Simulation mean critical gap is varied between 3s and 8s, while offered gap rate is varied between 0.05veh/s and 0.55veh/s. This study affirms that MLE provides a close to perfect fit to simulation mean critical gaps across a broad range of conditions. The MCG method also provides an almost perfect fit and has superior computational simplicity and efficiency to the MLE. The SWCG method performs robustly under high flows; however, poorly under low to moderate flows. Further research is recommended using field traffic data, under a variety of minor stream and major stream flow conditions for a variety of minor stream movement types, to compare critical gap estimates using MLE against MCG. Should the MCG method prove as robust as MLE, serious consideration should be given to its adoption to estimate critical gap parameters in guidelines. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
48.
The ability of conventional South African travel analysis practices to analyse adequately the travel needs of the poor is examined. The origins and nature of conventional practices are described, and it is observed that typically their scope has been limited to motorized modes, commutes and peaks. The paper reports on the findings of an activity diary survey administered in Cape Town that extended the conventional scope of analysis. An activity‐based survey method was selected because it typically yields higher rates of trip recall than other methods and is therefore relatively well suited to investigating travel behaviour in its fuller complexity. Selected findings of the survey are presented to demonstrate that travel occurring by non‐motorized modes, for non‐work purposes and during off‐peak periods, is considerable. It is argued that the conventional limitation in analytical scope can create serious misconceptions of the true nature of travel behaviour, particularly of low‐income households. By restricting the focus of analysis to motorized, work and peak period trip‐making, there is a risk of a routine bias being introduced in the way the urban passenger transport problem is understood, and in the nature of the interventions that are implemented as a result.  相似文献   
49.
This workshop considered the wider public policy goals of a range of transport interventions. Particular attention was paid to assessing the role of integration of the different components of the transport system and of the integration of transport with other economic sectors. This assessment was informed by Ray Pawson’s realist evaluation approach, with its emphasis on the inter-relationships between context, process and outcome. The context was provided by case studies covering small urban areas, large urban areas and inter-urban corridors. The three key processes identified related to a regulated system with public ownership and control, a deregulated system with private sector ownership (‘competition in the market’) and a system in which there was public planning of the transport system but private provision (‘competition for the market’). Outcomes can be assessed using cost-benefit analysis tools to determine impacts on economic welfare or more qualitative approaches can be used to determine the extent to which accessibility or sustainability goals have been achieved. The evidence provided suggests that wider public policy goals are more important for urban than for inter-urban transport and it thus in urban areas where integration should be pursued with most vigour. The most relevant process for achieving this would seem to be variants of the competition for the market model. Some policy recommendations are made and implications for further research and for future conferences assessed.  相似文献   
50.
The 1998 White Paper proposed integration as the solution to Great Britain’s land transport problems. Most commentators agree that this much vaunted New Deal for Transport has been a failure. Yet some ten years later policy papers from bodies such as the Institution of Civil Engineers and the Centre for Cities are still proposing integration as a possible panacea.There are a number of reasons for the failure of integrated transport over the last decade. The first is the failure to define the concept. The second is the failure to operationalise the concept. The third is the lack of an evidence base on the success of integrated transport policies. Evidence is now emerging in Britain on the benefits (and indeed the costs) of some aspects of integrated transport policies. The fourth, and perhaps the most crucial, is the lack of will in terms of politicians, civil servants and the public at large, to adopt the behavioural changes necessary for an integrated transport policy to be successful. A series of organisational and funding changes are proposed that could advance the prospects for integration.  相似文献   
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