Fundamental Issues in Suspension Design for Heavy Road Vehicles

Heavy road vehicles play an important role in the economy of many countries by providing an efficient means of transporting freight. Such vehicles can also have a significant impact on safety, the infrastructure and the environment. The design of the suspension affects the performance of the vehicle in terms of ride, infrastructure damage, suspension working space, energy consumption, rollover stability, yaw stability, braking and traction. The published literature on suspension design for heavy road vehicles is reviewed. It is found that extensive knowledge exists, but that there are areas where improved understanding is needed. Areas identified as fundamental issues requiring attention include ride discomfort criteria, secondary suspensions, and controllable suspensions. Two issues in particular are examined in detail: suspension tuning and suspension configuration. In the tuning of suspension parameter values for vibration performance, numerical optimisation techniques have been used extensively, but generic tuning strategies have not been widely developed. Modal analysis is proposed as a technique for gaining the insight into vehicle vibration behaviour necessary to enable tuning strategies to be devised. As an example, the technique is applied to the pitch-plane vibration of a tractor-semitrailer. In analyses of new suspension configurations or concepts, comparison with alternative concepts is not always made. Lack of such comparisons makes the selection of an optimum concept difficult. Analysis of alternative concepts using simple mathematical models, and comparison of their performance using common criteria, is advocated for enabling informed selection of an optimum. An example involving two alternative roll control systems is used to demonstrate the issue.     

Time-series model for vehicle speeds

This paper presents a time-series model for the spot speeds of vehicles on a road section. Based on time-series analysis techniques, the model incorporates information on the extent of existing dependency between the speeds of successive vehicles. The model for the data is chosen while relying heavily on the data, and thus emphasis is given to their special characteristics. The advantages of using the model are examined with regard to the relative speed of two successive vehicles along a road section. The results are compared with those obtained by using a model of independent observations; fewer errors are obtained with the time-series model. Therefore, it is concluded that the sequence of speed observations contains valuable information which should be incorporated into speed models.     

The EEZ and the progress of fisheries negotiations January to May 1977

This paper discusses negotiations, relative to sea fisheries, in terms of international arrangements—arrangements between the European Economic Community (EEC) and Third Countries; and those between member states of the EEC.     

Safety of child passengers who ride to school on a motorcycle: An observational study in two Argentine cities

In low- and middle-income countries, the motorcycle has increasingly become a means of family transportation due to its low cost and the poor quality of public transportation. Consequently, many child motorcycle passengers are at an elevated risk of serious injury in the event of a traffic crash. The available research on child safety devices is scarce and focused mainly on helmet use, while other devices (e.g. high-visibility clothing) have received little attention. This observational study documented the safety conditions and related factors of primary schoolchildren who rode to school as motorcycle passengers in two cities of Argentina.Data was obtained in the vicinity of 27 public primary schools in two cities of Argentina (one mid-sized city and the other a small city by the country's standards) between May 2018 and September 2019. A total of 1440 motorcycle occupants (656 drivers and 784 child passengers) were observed.The use of an adequate helmet was lower among children (vs. drivers). Most of the children were unable to reach the motorcycle's footrests, did not use high-visibility clothing or a fastening device, carried a backpack, and mounted and dismounted the motorcycle in an unsafe place. Some children rode in front of the driver or in a motorcycle with three or four occupants. Use of helmet by drivers and driver sex (woman) were related with an increase in safety in children. The indicators were worse in the larger city.The results revealed a low level of adoption of safety measures in children as well as in adults in both cities. This suggests that motorcycle travel is unsafe. Greater effort is needed to improve motorcycle safety, especially for children. It is important to debate regulatory details such as a minimum age for passengers, a limit on the number of passengers, and other safety criteria. It is also important to conduct educational campaigns that include the distribution of safety devices.     

Unsteady finite-depth effects during resistance tests on a ship model in a towing tank

This paper covers an extension of the study of Doctors et al. (J Ship Res 52(4):263–273, 2008) on oscillations in wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model to the case of relatively shallow water. We demonstrate here that the unsteady effects are very prominent and that it is essentially impossible to achieve a steady-state resistance curve in a towing tank of typical proportions for a water-depth-to-model-length ratio of 0.25. This statement is particularly true in the speed region near a depth Froude number of unity. However, on the positive side, we show here that an application of unsteady linearized wave-resistance theory provides an excellent prediction of the measured total resistance, when one accounts for the form factor in the usual manner. Finally, a simple application of the results to the planning and analysis of towing-tank tests is presented.     

Legal and institutional factors affecting mariculture in texas

Abstract

Aquaculture and its specialized cousin, mariculture, provide some potential additional food sources and economic revenues. Technological barriers to increased mariculture production are being removed, but many legal and institutional barriers remain. Examples of the current and potential regulation of mariculture in Texas by state and federal authorities are examined. The effect of various state and federal regulations on the development of mariculture is discussed from a legal and institutional viewpoint. The potential for growth of mariculture is considered questionable without regulatory reforms, particularly at the federal level.     

Transport economics: A personal view

The field of transportation attracts individuals from diverse backgrounds, seeking to make contributions to policy, planning, operations and strategy. Economists are one of the more visible subsets of players, who bring a specific focus to the transport problem. The key theme of this paper is economic efficiency and ways that transport economics seeks to achieve efficient outcomes in the presence of markets and institutions that to varying degrees distort the potential to fulfil this primary goal. We review some of the recent contributions to the literatures on institutional and market reform, travel choice and demand. As we enter the next century, there is a sense of promoting ‘back to basics’ (and redefinition of what skills transport specialists will require) in seeking a better understanding of the role of markets and institutions in guiding the destiny of the transport sector.     

The traffic and behavioral effects of the I-35W Mississippi River bridge collapse

On August 1, 2007, the collapse of the I-35W bridge over the Mississippi River in Minneapolis abruptly interrupted the usual route of about 140,000 daily vehicle trips, which substantially disturbed regular traffic flow patterns on the network. It took several weeks for the network to re-equilibrate, during which period travelers continued to learn and adjust their travel decisions. A good understanding of this process is crucial for traffic management and the design of mitigation schemes. Data from loop-detectors, bus ridership statistics, and a survey are analyzed and compared, revealing the evolving traffic reactions to the bridge collapse and how individual choices could help to explain such dynamics. Findings on short-term traffic dynamics and behavioral reactions to this major network disruption have important implications for traffic management in response to future scenarios.