An Alternative to the Roll Axis for Use in Commercial Vehicle Simulation

Vehicle dynamicists have frequently assumed that the roll motions of the sprung mass take place about a roll axis. Equations of motion based on this assumption must be expected to exhibit dynamic coupling, a significant complication in the case of digital computer simulations of multi-unit vehicles.

Digital simulations have been developed which, while preserving the physical character of the roll axis formulation, use further approximations to avoid the dynamic coupling. Validation exercises have been performed which demonstrate the accuracy of this methodology.     

Road pricing: An international perspective

This paper reviews experience with road pricing in Europe and Asia. It considers the objectives of road pricing, and demonstrates that differences in objectives lead to differences in scheme design and performance. It reviews the criteria for design of road pricing systems, and the development of charging structures and technologies to meet those criteria. In particular it discusses the relative merits of pre-determined and congestion-dependent charging structures, and of off-vehicle and on-vehicle charging systems. It assesses the performance of road pricing systems to date, discusses objections to road pricing and demonstrates that the role of road pricing within a wider transport strategy and the use made of the revenue generated, will be important determinants of public acceptability. Finally it assesses the relative merits of alternative approaches to implementation and argues that these will need to pay as much regard to public acceptability as to technical performance.     

The importance of attitudes in the decision to use mass transit

This paper reports the results of tests of the hypotheses that attitudinal variables are important in mode choice decisions and that they can significantly increase the explanatory power of network-based mode choice models. Conflicts between the results of previous work by Lovelock and Johnson are resolved by this study. Attitudinal items used by Johnson and by Lovelock in separate studies in the San Francisco Bay area were included in a survey of Chapel Hill households. Tests of the incremental explanatory power of the attitudinal variables in mode choice models confirm that the items used by Johnson do not contribute to the explanatory power of models using network time and cost data. Similar tests showed that Lovelock's attitudinal items do significantly increase the predictive ability of the models. The conflicting results of these previous studies are therefore due to the content of the items. Attitudinal data, including both attitude items and measures of perceptions of system attributes, do enhance the predictive power of models involving network data.This research was supported by a grant from the Urban Mass Transportation Administration, U.S. Department of Transportation, Washington, D.C.     

Development of a Strategy Model of the Driver in Lane Keeping

Based on vehicle constraints and known human operator characteristics, a strategy model was postulated for describing behavior in the lane keeping task. This model includes nonlinear thresholds operating on vehicle yaw and lateral translation, random input sources to account for spurious driver activity, and smoothing to account for driver response lag. The output of the model is steering wheel position

To determine model parameters and model suitability in describing driver behavior, recordings were made for driver-subjects performing a lane-keeping task in a moving base driving simulator having a computer generated display. A procedure involving both analytic and experimental techniques was then developed for determining the model parameters of each driver

Statistical comparisons and visual inspections made between driver-vehicle and model-vehicle time histories indicate a high degree of correspondence. Models such as these show promise in obtaining a better understanding of driver behavior and driver-vehicle response by incorporating nonlinear elements in the driver model.     

Toward criteria in the development of urban transportation systems

Improved criteria are necessary to aid in determining awards of federal funds for metropolitan transit projects. Commuting is the main use for public transit. Thus a primary objective of an urban transit system should be to provide a flexible and balanced set of options to the workers in the metropolitan area for their journey to work. This paper discusses various facets of an appropriate balance among the three modes: rapid rail, bus, and automobile. Three cities are selected for further analysis: Baltimore, Kansas City, and Phoenix. These cities represent different stages in economic-transportation development, and also present different spatial patterns of residence and employment. The applicability of rapid rail transit to each city is examined in view of central city worker concentration and recent trends.     

Internal tidal currents in the Gaoping (Kaoping) Submarine Canyon

Data from five separate field experiments during 2000–2006 were used to study the internal tidal flow patterns in the Gaoping (formerly spelled Kaoping) Submarine Canyon. The internal tides are large with maximum interface displacements of about 200 m and maximum velocities of over 100cm/s. They are characterized by a first-mode velocity and density structure with zero crossing at about 100 m depth. In the lower layer, the currents increase with increasing depth. The density interface and the along-channel velocity are approximately 90° out-of-phase, suggesting a predominant standing wave pattern. However, partial reflection is indicated as there is a consistent phase advance between sea level and density interface along the canyon axis.     

Freight forwarders speak: the Perception of Route Competition via Seaports in the European Communities Research Project. Part 1

This paper, in two parts, reports on the Perception of Route Competition via Seaports in the European Communities Research Project wherein a total of 72 interviews were held in 11 European countries. Respondents were also asked to fill in a questionnaire, and it is these questionnaire findings that are reported in this first part of the paper. These is a perhaps surprisingly widespread belief that frequency of shipping service is a main reason for choice of seaport in cargo movement. Time on the route and labour problems at ports are major concerns of freight forwarders whose minds are powerfully imbued with the spirit of free enterprise(absence of governmental or other planning agency intervention). Among other major conclusions are a preference for 'delivered price' consignments and the belief in the importance of port charges in route determination (see table 2 for summary of major conclusions).