Pivot point-based control for active rear-wheel steering in passenger vehicles

This paper presents a new application of active rear-wheel steering control to improve the lateral vehicle behaviour. In the state of the art, yaw or lateral velocity is used as control variable that means one degree of freedom being not directly controlled. A worse subjective impressions due to movements in the rear end of the vehicle during strong counter-steering are a consequence. To avoid this effect in urban surroundings, an innovative structure to control the pivot point distance of the vehicle is proposed. In this case the coupled elementary states yaw and lateral velocity can be influenced based on a higher level criteria. Analysis show that pivot point fixing provides a comprehensible reference behaviour. Solving the issue of singularity during disappearing yaw movement is the basis to design a performant modified feedforward input–output linearisation. An analytic stability analysis of the internal dynamics shows system immanent limitations which do not influence the target of improving the lateral vehicle dynamics in urban manoeuvres. Finally, the advantages of pivot-based control are highlighted by a comparison with state of the art rear axle control.     

An analytical approximation for the macroscopic fundamental diagram of urban traffic

This paper shows that a macroscopic fundamental diagram (MFD) relating average flow and average density must exist on any street with blocks of diverse widths and lengths, but no turns, even if all or some of the intersections are controlled by arbitrarily timed traffic signals. The timing patterns are assumed to be fixed in time. Exact analytical expressions in terms of a shortest path recipe are given, both, for the street’s capacity and its MFD. Approximate formulas that require little data are also given.For networks, the paper derives an upper bound for average flow conditional on average density, and then suggests conditions under which the bound should be tight; i.e., under which the bound is an approximate MFD. The MFD’s produced with this method for the central business districts of San Francisco (California) and Yokohama (Japan) are compared with those obtained experimentally in earlier publications.     

An intersection control strategy for a short‐headway P.R.T. network

Much PRT development and research is currently being undertaken assuming quasi‐synchronous longitudinal control of guideway vehicles. This method of control has the characteristic that intersection performance has a substantial influence on the efficiency of trip demand processing. An algorithm for the control of a PRT intersection is discussed here, which would appear to have significant advantages over all other known existing stratagems. The stratagem is not only efficient but its flexibility facilitates tailoring to diverse local conditions; furthermore, the algorithm does not require intractable computations or excessive computer memory requirements. The algorithm is described and simulation results are presented. A comparative study is also made between this algorithm and its fore‐runner.     

Public law litigation and marine affairs: The boldt decision

Abstract

The management and conservation of the marine environment and its natural resources are increasingly understood to be issues of public policy with consequences for society at large. On a variety of dramatic occasions over the last decades, the federal judiciary has departed from its traditionally passive role in the shaping of social policy. This paper examines a critical marine controversy, the Boldt Decision (U.S. v. Washington 1974), to illustrate and evaluate nontraditional judicial behavior. The first two sections introduce Indian‐United States treaties concerning Pacific Northwest salmon resources, and the unfolding of the Boldt Decision. A third section argues that a “public law”; model of litigation fits the legal events of the Boldt Decision. A fourth section addresses the competence of the Boldt court as it is manifest in judicial organization, analysis, and implementation. A final section comments on the potential for public law litigation elsewhere in the governing of marine affairs.     

Interurban road network planning model with accessibility and robustness objectives

Abstract

Road network planning (or design) problems consist of determining the best investment decisions to be made with regard to the improvement of a road network. In this paper, we propose an optimization model for long-term interurban road network planning where accessibility and robustness objectives are simultaneously taken into account. Three network robustness measures were defined to assess different robustness concerns: network spare capacity; city evacuation capacity; and network vulnerability. The results that may be obtained from the application of the model are illustrated for three random networks. Special attention is given to the implications of adopting each one of the robustness measures upon the optimum solution provided by the model.     

Book reviews

R. S. Farrow, with J. M. Broadus, T. A. Grigalunas, P. Hoagland III, and J. J. Opaluch. 1990. Managing the Outer Continental Shelf Lands: Oceans of Controversy. New York: Taylor & Francis New York, 168 pp., paper.

Richard A. Kenchington. 1990. Managing Marine Environments. New York: Taylor & Francis, 248 pp.     

The container terminal community

This paper is an initial exploration of inter-industry relationships and linkages in the context of automobile imports to the United States. It is our contention that the nature and structure of the engagement between automobile importers and shipping lines is central to understanding the evolution of the car carrier trade. Building on the literature on transactions costs, and supply and value chains, we show that the regimes currently governing car carriage services range from markets to vertical integration via network forms of engagement. We illustrate this through a detailed discussion of Japanese inter-firm networks and an examination of automobile import data to the US from 1980 to 2000. The findings raise important questions for future research on the impact of inter-industry relationships in various strategic decisions of steamship lines, shippers and port authorities including port entry, port choice and routeing, technological and investment choices, and trajectories of supply chain development.     

Analyzing the structure of informal transit: The evening commute problem

Through the use of a profit-maximizing continuum approximation model, this paper systematically analyzes the development and structure of informal transit systems as a function of the network, user, and modal characteristics. This study examines the evening commute problem along a linear corridor where passengers originate uniformly from a central business district and have destinations uniformly distributed along the corridor. Informal transit drivers who are profit-maximizing will be compared against the traditional case of coordinated, government service that aims to maximize the total welfare. Policies, such as fare regulation and vehicle licensing schemes, will be presented to help rationalize informal transit service using a government-operated service as the baseline.     

The opinions and attitudes of Louisiana's Coastal Zone residents toward outdoor recreational development: A perspective for planning and management

Abstract

In 1967, a new road facilitated access to a number of small, impoverished, rural communities in a marshy region along Mexico's Pacific coast. One of these—the only one situated on the Pacific shore—began to be visited by an increasing stream of tourists. This article discusses the severe sociocultural problems which the initial phase of tourism development caused in Teacapán, and argues that these are part of a syndrome which is manifest in similar situations worldwide. By anticipating this syndrome before tourism development gets underway, planners and managers of coastal tourism development in Third World nations would be better prepared to mitigate most of its severe effects.