An analytical formula of driver RMS acceleration response for quarter-car considering cushion effects

In this paper, a 3-DOF (degree-of-freedom) model of quarter-car coupled with driver and cushion is used to derive an analytical formula, which can describe the driver RMS (root-mean-square) acceleration response with cars under random excitation generated by road irregularities. The study starts with the 3-DOF model. Based on the vehicle random vibration theory, using the residue theorem, the analytical formula of driver RMS acceleration considering cushion effects is obtained. Then, the driver RMS acceleration values calculated from the measured data and from the analytical formulae of the 3-DOF and the classical 2-DOF model are compared. The results show the analytical formula for the 3-DOF model provides a more reasonable approximation of the real response of the test car. Having obtained the analytical formula, the effects of vehicle parameters on driver RMS acceleration are studied. Finally, to provide critical foundations for the selection of the cushion damping, the optimal damping ratio of driver-cushion system is deciphered from the analytical formula. To uncover how each dynamic parameter effects the optimal damping ratio, the analysis of influencing factors is performed and some important conclusions are obtained. The derived analytical formula can be also conveniently used either during preliminary design or for other special purposes.     

驾驶员适时加速对城市道路通行能力影响的调查与分析

对北京海淀区学清路口及学院桥路口交通状况进行了实际调查,针对交通现状,进行理论与实际分析,讨论驾驶员适时加速对城市道路通行能力的影响。     

Clarifying multiple-mode decision making in conventional psychological models: A consideration of the influential mechanism of car use's characteristics on the behavioral use of public transportation

The existence of the multiple-mode decision making process challenges the existing psychological theories those predict travel behaviors because the theories were mainly to explain the relationship between travelers' perceived attributes of a targeted mode, not to make choices between modes. A review of related literatures showed a lack of focus on the mechanism of one mode influencing other mode in psychological models. The present study investigates how car-related factors affect the establishment of bus use intention in a psychological investigation. It is hypothesized that single car use factors do not directly influence bus use intention, rather than that; they indirectly influence bus use intention through an overall factor of car use. Results from a dataset of 270 samples investigating three types of daily trips in the Japanese context showed support to the mediating effect of the overall car use factor. As such, an arbitrary inclusion of car-related factors to psychological models of public transportation may not be recommended.     

Investigation of helmet use behavior of motorcyclists and effectiveness of enforcement campaign using CART approach

Use of the helmet is beneficial in reducing the severity of injuries and avoiding fatalities for motorcyclists, therefore, legislation exists in almost all countries. In practice, the situation is different regarding the helmet use, especially in the developing countries. This paper investigates the helmet use behavior of motorcyclists in Karachi, Pakistan. It determines the significant factors affecting the helmet use in Karachi (Pakistan) and recommending effective campaign measures to promote helmet use. It is vital in relation to the exponential growth of motorcycle users and poor enforcement of traffic rules. Repeated cross-sectional data collected before (n = 226) and after (n = 277) the helmet use enforcement campaign is analyzed using univariate and non-parametric classification and regression tree (CART) techniques. A significant number of motorcyclists do not hold a driving license and CART analysis highlighted the significance of this variable along with exposure to the road environment (measured as daily usage of motorcycle) to explain helmet use. Campaign effects are found temporary, therefore, serious efforts are required to design coherent and structured awareness and enforcement programs.     

Measuring the safety impact of road infrastructure systems on driver behavior: Vehicle instrumentation and real world driving experiment

Featured in this pilot experimental study is the construction and design of an instrumented vehicle that is able to capture vehicle trajectory data with an extremely high level of accuracy and time resolution. Once constructed and properly instrumented, the various data collection systems were integrated with one another and a driving experiment was conducted on northern Virginia roadways with 18 participants taking part in the study. Trajectory data were collected for each of the drivers as they traversed a predefined loop of four roadway segments with varying numbers of lanes and varying shoulder widths. Data collected from the experiment were then used to calibrate the parameters of the prospect theory car-following model through a genetic algorithm calibration procedure. Once all model parameters were successfully calibrated, significance testing was carried out to determine the impacts that the varying roadway infrastructure had on driving behavior. Results indicated that there were significant changes in behavior when comparing one lane roadways to their two lane counterparts—specifically in cases where the roadway featured a wide shoulder. Additional testing was conducted to ensure that there was no variation based on gender, as nine study participants were female and nine were male. The successfulness of this first study conducted with the newly constructed instrumented vehicle creates the opportunity for a variety of additional studies to be conducted in the future.     

A study on the timing of Asian metropolitan railway development with motorization and its effect on CO2 emissions from transportation

In metropolitan areas of developing and emerging economies in Asia, a remarkable phenomenon of motorization with rapid economic growth is accelerating a continuous formation of auto-dependent urban structures. The delayed timing of urban railway introduction could contribute to a negative spiral of motorization, which could provoke a severe increase in CO₂ emissions from transportation sector. In this paper, we attempt to evaluate the timing of urban railway station development based on the level of automobile share and an analysis of the CO₂ emissions in the catchment areas of newly introduced urban railway stations in Asian metropolitan areas; Japan, Malaysia and Indonesia. The result quantitatively reveals that the earlier development of the stations in comparison to the progress of motorization tended to result in a statistically significant reduction of CO₂ emissions from transportation year-by-year in the catchment areas. In addition, this study demonstrates statistically that urban development harmonized with urban railway systems with a higher service frequency should be a key factor on the strategic realization of low-carbon urban forms along public transportation corridors.     

杭州湾大桥抗风性能试验研究

杭州湾大桥为目前世界最长的跨海公路大桥,包括南航道和北航道两座大跨度桥梁。对杭州湾大桥北航道桥成桥状态、最大双悬臂状态及最长单悬臂状态进行了动力特性分析,介绍了节段模型风洞试验的主要内容、试验结果, 据此分析评估了该桥的抗风性能,并得出了一些有益的结论。