从全球角度透视巴拿马运河扩建及海运业的发展(英文)

2007年6月13日,巴拿马运河管理局在上海浦东香格里拉大酒店举办“巴拿马海运日”,巴拿马运河管理局国际顾问委员会主席、国际海事组织(IMO)前秘书长威廉·A·奥尼尔先生在开幕仪式上发表了演讲。奥尼尔先生的讲话着重强调海运在当代经济和社会发展中不可替代的巨大作用,集装箱化又是影响最大的因素之一,而且在可持续发展大趋势下,海运又是能效最高、对生态环境最友好的运输方式。演讲还指出海运事业广泛的国际性以及各国政府在政策法规等方面合作和协调对发展全球海运业的重要意义。奥尼尔先生高度赞扬巴拿马运河回归后的出色管理,以及运河在21世纪,尤其是在扩建计划完成后,对世界航运业的重大贡献。应本刊之约,讲演稿由作者修改后发表如下。     

Monitoring long-term environmental change: Some lessons from Sullom Voe,Shetland Islands

The impact on the marine environment of the operation of the Sullom Voe Oil Terminal and its major port facility in the Shetland Islands has been monitored continuously for more than twenty-five years. The site of this very large terminal straddles a peninsula and the separation of the impact of the port on the sheltered west side (Sullom Voe) and the aqueous discharge from the terminal to the east, into the strong tidal current of Yell Sound, has proven to be advantageous. There are two types of monitoring, statutory (to comply with relevant legislation) and voluntary (to establish good practice and to examine a wider range of impacts e.g. island-wide ornithology). The latter function is undertaken by an independent advisory committee (SOTEAG). Over time, the nature and amount of voluntary monitoring has decreased in response to the long term evidence that both terminal and port operations are having little or no impact on a wide range of habitats and species. Voluntary monitoring also acts as an independent check on both compliance and other forms of environmental assessment. Although the terminal is now operating at less than half its peak capacity, this does not mean that there has been apro-rata decrease in monitoring activity.     

General stochastic user equilibrium traffic assignment problem with link capacity constraints

This paper addresses a general stochastic user equilibrium (SUE) traffic assignment problem with link capacity constraints. It first proposes a novel linearly constrained minimization model in terms of path flows and then shows that any of its local minimums satisfies the generalized SUE conditions. As the objective function of the proposed model involves path‐specific delay functions without explicit mathematical expressions, its Lagrangian dual formulation is analyzed. On the basis of the Lagrangian dual model, a convergent Lagrangian dual method with a predetermined step size sequence is developed. This solution method merely invokes a subroutine at each iteration to perform a conventional SUE traffic assignment excluding link capacity constraints. Finally, two numerical examples are used to illustrate the proposed model and solution method.     

Modeling the Effects of Population Density on Prospect Theory-Based Travel Mode-Choice Equilibrium

In conventional transportation planning models, it was always assumed that the population density is given and fixed in the study areas. Therefore, the effects of population density on travel choice have not been explicitly incorporated into these existing models for long-term transportation planning. Meanwhile, travel choice models in previous studies are usually developed by using discrete choice theories or user equilibrium principle. Thus, many significant characteristics of travelers’ behaviors, such as risk preference and learning process over time, cannot be considered in these conventional models. This article proposes a convex prospect theory-based model to investigate the effects of population density on the travelers’ mode-choice behavior under an advanced transportation information system (ATIS) in a multimodal transportation corridor. It is shown that population density is closely co-related to the modal split results and dependent on the performance of the railway mode in the study corridor. The park-and-ride mode may not be suitable for areas with high population density. This article also investigates the travelers’ reference points on the generalized travel costs by modes. A numerical example is given to illustrate the properties of the proposed model together with some insightful findings.     

Alternatives in assigning short‐term counts to seasonal adjustment factor groupings

The precise estimation of the annual average daily traffic (AADT) is a task of significant interest for many transportation authorities and Departments of Transportation. In this study, three methods are developed to improve the assignment of short‐term counts to seasonal adjustment factor (SAF) groupings: the traditional functional classification, a discriminant analysis (DA), and a new statistical approach based on a weighted coefficient of variation (WCV). The data analyzed within this study are generated from all available continuous counters within the State of Ohio between 2002 and 2006. The analysis is conducted using SAFs that are separately calculated for the total volume and the directional specific volumes of a site. The results show that the directionally based assignment errors are statistically lower at a 95% confidence interval when compared with those generated by the total volume analysis. It is also found that the hourly time‐of‐day factors are more important in the assignment process than the average daily traffic. The directionally based WCV produces a decline in the average mean absolute percentage error (MAPE) over the roadway functional classification by 58% and in the standard deviation of the absolute error (SDAE) by 70%. On the contrary, the directionally based DA lowers the MAPE and the SDAE by 35% and 60%, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

An optimization model for bus fleet replacement with budgetary and environmental constraints

ABSTRACT

As maintenance and operation costs increase with usage over time, equipment is replaced when the value of new equipment is more attractive. Some methods have been developed to solve this problem. In the public transport sector, such problems are frequently analyzed by fleet managers and determined by bus age restriction regulations. We propose an Integer Programming model that integrates both budgetary and environmental constraints (CO₂ emissions) which, as far as we know, have not previously been studied in conjunction. The study aims to determine the optimal replacement plan for a fleet of diesel buses of different size, age, maintenance costs and emissions rates, with new (less polluting) diesel buses over a time horizon of 50 years. The results indicate that it is possible to reduce emissions with a low annual budget using an optimal replacement policy.     

Autonomous vehicles: who will use them,and will they share?

ABSTRACT

The advent of road transport automation is suggested to be one of four key technological transitions that could amount to a major transformation in mobility practices. Specifically, fully Automated Vehicles (AVs) might replace the current private car owner user model with fleets of on-demand synchronously-shared automated taxis. However, significant barriers to this vision becoming the norm remain. This paper examines two critical user-acceptance aspects of the transition: willingness to adopt AVs, and willingness to share an AV with others, particularly strangers. Our novel survey (n?=?899) included a choice experiment featuring four future full automation transport services (private, synchronously/asynchronously shared, and public). Cluster analysis examined respondents' preferences and their demographic and psycho-social characteristics. We uncover significant uncertainty about willingness to adopt automation and sharing, and important differences between clusters within our sample. For example, under 50% of participants report willingness to use an AV over their normal mode, or would prefer an automated option to a current human-driven option. Our findings raise critical questions for policymakers and transport authorities. Not least, how can AV technologies help realise the environmental and social benefits of widespread vehicle sharing in a context of a travelling public that still prefers its privacy on-the-move?