Urban transportation modeling: The discussion continues

This article is a response to John Polak's article, entitled, A Comment on Supernak's Critique of Transport Modeling, published elsewhere in this issue of TRANSPORTATION. It offers necessary clarifications to the issues discussed in an earlier article in this journal (Supernak, 1983). It also responds to the philosophical issues discussed in Polak's article, such as the nature of transport phenomena, and the role, form and methodology of transport modeling.     

Towards connected autonomous driving: review of use-cases

Connected autonomous vehicles are considered as mitigators of issues such as traffic congestion, road safety, inefficient fuel consumption and pollutant emissions that current road transportation system suffers from. Connected autonomous vehicles utilise communication systems to enhance the performance of autonomous vehicles and consequently improve transportation by enabling cooperative functionalities, namely, cooperative sensing and cooperative manoeuvring. The former refers to the ability to share and fuse information gathered from vehicle sensors and road infrastructures to create a better understanding of the surrounding environment while the latter enables groups of vehicles to drive in a co-ordinated way which ultimately results in a safer and more efficient driving environment. However, there is a gap in understanding how and to what extent connectivity can contribute to improving the efficiency, safety and performance of autonomous vehicles. Therefore, the aim of this paper is to investigate the potential benefits that can be achieved from connected autonomous vehicles through analysing five use-cases: (i) vehicle platooning, (ii) lane changing, (iii) intersection management, (iv) energy management and (v) road friction estimation. The current paper highlights that although connectivity can enhance the performance of autonomous vehicles and contribute to the improvement of current transportation system performance, the level of achievable benefits depends on factors such as the penetration rate of connected vehicles, traffic scenarios and the way of augmenting off-board information into vehicle control systems.     

On the use of mathematical programming in the evaluation of transport policies

This paper focuses on the evaluation processes by which decisions regarding transportation alternatives can be assisted. A multidimensional approach usually called multiple criteria decision making is required to represent the complexity of transportation policy and systems.

The multiple criteria decision making techniques can be divided into two groups. The first is based on a ranking scheme approach and the second on a mathematical programming approach.

A multiple objective mathematical programming procedure known as Goal Programming is presented. The authors examined the use of that procedure in real transportation problems.

The results suggest that multiple objective mathematical programming techniques in general do not appear to be appropriate in transportation policy analysis involving mutually exclusive alternatives. Their use can be limited to special cases in the private sector.     

新型压接式IGBT模块的结构设计与特性分析

介绍了一种新型压接式绝缘栅双极型晶体管(Insulated Gate Bipolar Transistor,简称IGBT)模块的内部结构设计,分析其相对于传统IGBT模块的优势,并通过静态和动态测试分析了其电气性能特点,展示了其良好的特性以及广阔的应用范围。     

Rigor and Representativeness in Marine Protected Area Design

Virtually all marine conservation planning and management models in place or proposed have in common the need for improved scientific rigor in identifying and characterizing the marine habitats and processes encompassed. An emerging central theme in the last few years has been the concept of representativeness, or representative systems of marine protected areas (MPAs). Representativeness and similar terms are used in two distinct senses in current literature, leading to considerable confusion. Definitions of these terms as they are currently used are provided. The habitat classification and mapping needed to incorporate considerations of representativeness into MPA planning must logically be carried out at the same scale at which management occurs. Management of highly protected areas is found to occur almost exclusively at local scales or finer, independent of the reservation model or philosophy employed. Current techniques for cost-effective surveying of marine areas are discussed. The emerging field of remote videography, in some cases linked with acoustic discrimination sensors, can provide quantitative data on real biological distributions. Such data lend themselves well to robust multivariate analysis in deriving habitat maps at scales relevant to managers, as a basis for assessing and planning for representation in MPA design.     

Maritime security in the European Union—empirical findings on financial implications for port facilities

To address the maritime security issue, the IMO Diplomatic Conference adopted in December 2002 the International Ship and Port Facility Security (ISPS) Code. The European Union fully agreed with its contents; Regulation (EC) No. 725/2004 transposes in Community Law the associated rules, which came into force on 1 July 2004. Interesting questions from an EU-policy point of view are then: What are the additional costs associated with the implementation of security regulations by port facilities (here in particular terminals) in EU-member states? Moreover, how are these additional costs being recovered by port facilities? Another inter-related question is: are there any subsidies involved in the cost recovery? The present paper addresses these questions with the presentation of the main results of an explorative empirical study on maritime security-related costs and their financing in EU-member states. Furthermore, a number of topics are recommended for further study on maritime security costs and financing and associated (EU) regulations.     

An idealized model of interaction between fronds of the large seaweed Durvillaea antarctica

The effect of interactions between individual fronds in a bed of the large intertidal seaweed Durvillaea antarctica, when forced by breaking waves, is studied using a computational model. The model simulates the response of a seaweed bed using a sequence of connected oscillators which are excited by a propagating forcing function representing a breaking ocean wave. Two new facets of the interplay between seaweeds and hydrodynamics are considered: (i) wave forcing due to breaking waves is often not sinusoidal in the rocky intertidal zone and (ii) a frond interaction term is included. The addition of frond interaction reduces the maximum loading on individuals within the bed by around 30% using estimated biomechanical parameters. The rate of change of the loading on the holdfast (equivalent to the “jerk”) is affected in a similar or greater fashion.     

Maritime security in the European Union—empirical findings on financial implications for port facilities

To address the maritime security issue, the IMO Diplomatic Conference adopted in December 2002 the International Ship and Port Facility Security (ISPS) Code. The European Union fully agreed with its contents; Regulation (EC) No. 725/2004 transposes in Community Law the associated rules, which came into force on 1 July 2004. Interesting questions from an EU-policy point of view are then: What are the additional costs associated with the implementation of security regulations by port facilities (here in particular terminals) in EU-member states? Moreover, how are these additional costs being recovered by port facilities? Another inter-related question is: are there any subsidies involved in the cost recovery? The present paper addresses these questions with the presentation of the main results of an explorative empirical study on maritime security-related costs and their financing in EU-member states. Furthermore, a number of topics are recommended for further study on maritime security costs and financing and associated (EU) regulations.     

Attitudinal models of modal choice: The multinomial case for selected nonwork trips

Attitudinal multinomial logit models of modal choice are presented for four nonwork activities: major grocery shopping, shopping for odds and ends, shopping for personal goods and visiting friends and acquaintances. Explanatory variables are individuals' beliefs about attributes of four modal alternatives: bus, car, taxi and walking. Factor analysis is employed to identify latent dimensions of perception of the modal alternatives and to eliminate problems of multicollinearities in model estimation. Models are estimated using data obtained for a sample of residents of Buffalo, New York. Planning implications of the methodology are assessed.This author is presently Systems Planner with Applied Resource Integration, Ltd., Boston, Massachusetts.     

How optimal was the Sydney Metro contract?: Comparison with international best practice

The New South Wales (NSW) government created the Sydney Metro Authority to design, build and operate a completely separate underground Metro rail system to supplement the existing public transport network in Sydney. By the time the NSW government abruptly cancelled the entire Metro project in early 2010, the Authority had conceived and designed a contract that was proceeding to procurement. This paper compares the elements of the proposed Sydney Metro contract to findings of the literature on optimal contracting and optimal incentives and on PPP best practice. The paper concludes that the Metro seems to have at least implicitly drawn fairly heavily on best practices and principles, but that its ultimate failure to be implemented is an instructive lesson about how operating environment can impede integration of useful knowledge and experience.