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641.
One of the biggest unresolved problems regarding the completion of the free internal transport market within the European community is the problem of harmonization of taxation on the road haulage industry. As the highest tax country, Britain might be expected to have to reduce its level of taxes as part of any harmonization. This paper considers the current methodology of the British Department of Transport regarding the allocation of the track and external costs of road transport, in the light of developments in methodology and experience elsewhere in Western Europe and North America. We find a number of reasons for believing that, far from overstating the marginal social cost of use of roads by the road haulage industry, the current British approach actually understates it. Thus any move towards harmonizing tax levels may reduce taxes in Britain at a time when they should be increasing. 相似文献
642.
Driving of off-road vehicles (ORVs) on sandy beaches is common and widespread, but is not universally embraced due to putative environmental impacts on beach biota. For ORVs to impact the beach fauna, traffic areas must overlap with faunal habitat: a fundamental pre-requisite for impact assessments but as yet un-quantified for sandy beaches. Thus, this study quantified the spatial and temporal patterns of ORV traffic on five Australian beaches, and measured the degree to which the distribution of intertidal macro-invertebrates overlaps with traffic zones. Traffic volumes on beaches can be considerable (up to 500 vehicles per day). The position of beach traffic across the beach-face is principally governed by tides and driver behavior. Despite driver education campaigns to the contrary, a considerable fraction of vehicles (16–67%) traverses the soft, upper shore near the foredunes. The majority (65%) of burrowing invertebrate species of the intertidal zone is directly exposed to traffic, save for species inhabiting the swash zone. Because beach traffic presents a formidable management challenge, a fundamental first step in identifying whether ecological impacts are indeed likely, is to assess the potential for spatial and temporal conflict between human pressures (e.g., ORVs) and biological resources (e.g., beach fauna). Although this potential is certainly substantial for sandy shores used by ORVs, the actual ecological impacts on the intertidal fauna can only be predicted in situations where the responses (e.g., direct mortality, behavioral changes) of individual species to beach traffic are known. 相似文献
643.
A.T.Kearney 《上海汽车》2018,(1)
正1城市智能交通下一个创新风口统计结果显示,我国一线城市私家车保有量年平均增速达到20%。有限的城市土地供应和快速增长的城市交通需求之间的矛盾日益凸显。根据高德地图的研究,相比2015年,2016年调研的45座主要城市中有80%的城市延时拥堵指数加重。其中,北上广深的出行高峰时期平均每小时拥堵时间长达29 min,对于出行居民的个人年拥堵成本达到9 500元,相当于个人年均收入的 相似文献
644.
Alfonso M. Panunzio Guillaume Puel Régis Cottereau Samuel Simon Xavier Quost 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(11):1768-1795
This paper investigates the effects of the track geometry irregularities on the wheel–rail dynamic interactions and the rail fatigue initiation through the application of the Dang Van criterion, that supposes an elastic shakedown of the structure. The irregularities are modelled, using experimental data, as a stochastic field which is representative of the considered railway network. The tracks thus generated are introduced as the input of a railway dynamics software to characterise the stochastic contact patch and the parameters on which it depends: contact forces and wheelset–rail relative position. A variance-based global sensitivity analysis is performed on quantities of interest representative of the dynamic behaviour of the system, with respect to the stochastic geometry irregularities and for different curve radius classes and operating conditions. The estimation of the internal stresses and the fatigue index being more time-consuming than the dynamical simulations, the sensitivity analysis is performed through a metamodel, whose input parameters are the wheel–rail relative position and velocity. The coefficient of variation of the number of fatigue cycles, when the simulations are performed with random geometry irregularities, varies between 0.13 and 0.28. In a large radius curve, the most influent irregularity is the horizontal curvature, while, in a tight curve, the gauge becomes more important. 相似文献
645.
John Jowhell Villegas Wael K.M. Alhajyaseen Hideki Nakamura Azusa Goto 《国际交通安全学会研究报告》2018,42(4):230-239
Signalized intersections are one of the key elements that play a vital role at road networks. The efficiency and safety levels of intersections can affect the operational performance of the whole system. In general, turning traffic, especially median-turning, has always been considered as the most problematic movement in the operation of intersections. This becomes more critical with high turning demand where exclusive turning lanes (single or double) can be assigned to provide larger capacities for these movements and to reduce conflicts with through traffic. However, improper treatment of median-turn lanes could create cross-maneuvering behavior which may limit the expected increase in capacity and create safety issues. Median-turning lane markings are commonly provided at intersections in Japan to guide drivers while turning which is expected to reduce the conflicts among turning traffic. Meanwhile, in the Philippines, exclusive median-turn lanes are installed at intersections without proper treatment which may contribute to the low mobility and safety levels. Therefore, this study evaluated the impact of inside intersection lane markings on the operation of median-turn lanes in terms of mobility and safety. The vehicle maneuver, speed and interactions between the turning traffic were utilized as essential components for the assessment. The empirical analysis shows that conflicting trajectories were present on double turn lanes without median-turn lane markings in the Philippines, which resulted to serious conflicts among the turning vehicles and negatively influenced the turning speed and saturation flow rate of the turn lanes. On the other hand, the turn lane markings in Japan, provided a positive impact to mobility and safety of the turning lanes. Moreover, it was also found that the geometric characteristics and traffic signal phasing scheme highly affects the capacity and safety condition of signalized intersections. 相似文献
646.
K. Six A. Meierhofer G. Müller P. Dietmaier 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2015,53(5):635-650
Friction within the wheel–rail contact highly influences all aspects of vehicle–track interaction. Models describing this frictional behaviour are of high relevance, for example, for reliable predictions on drive train dynamics. It has been shown by experiments, that the friction at a certain position on rail is not describable by only one number for the coefficient of friction. Beside the contact conditions (existence of liquids, solid third bodies, etc.) the vehicle speed, normal loading and contact geometry are further influencing factors. State-of-the-art models are not able to account for this sufficiently. Thus, an Extended-Creep-Force-Model was developed taking into account effects from third body layers. This model is able to describe all considered effects. In this way, a significant improvement of the prediction quality with respect to all aspects of vehicle–track interaction is expected. 相似文献
647.
648.
A. Karnwal M. M. Hasan N. Kumar A. N. Siddiquee Z. A. Khan 《International Journal of Automotive Technology》2011,12(4):599-610
This paper presents an experimental study that involves an application of the Taguchi method and grey relational analysis
to determine the optimum factor level to obtain optimum multiple-performance characteristics of a diesel engine run with different
low-percentage thumba biodiesel-diesel blends. Four factors, namely, low-percentage thumba biodiesel-diesel blend, compression
ratio, nozzle opening pressure and injection timing were each considered at three levels. An L9 orthogonal array was used to collect data for various engine performance- and emission-related responses under different
engine loads. The signal-to-noise (S/N) ratio and grey relational analysis were used for data analysis. The results of the
study revealed that the combination of a blend consisting of 30% thumba biodiesel (B30), a compression ratio of 14, a nozzle
opening pressure of 250 bar and an injection timing of 20° produces maximum multiple performance of a diesel engine with minimum
multiple emissions from the engine. 相似文献
649.
P. V. Manivannan M. Singaperumal A. Ramesh 《International Journal of Automotive Technology》2011,12(1):11-20
An idle speed engine model has been proposed and applied for the development of an idle speed controller for a 125 cc two
wheeler spark ignition engine. The procedure uses the measured Indicated Mean Effective Pressure (IMEP) at different speeds
at a constant fuel rate and throttle position obtained by varying the spark timing. At idling conditions, IMEP corresponds
to the friction mean effective pressure. A retardation test was conducted to determine the moment of inertia of the engine.
Using these data, a model for simulating the idle speed fluctuations, when there are unknown torque disturbances, was developed.
This model was successfully applied to the development of a closed loop idle speed controller based on spark timing. The controller
was then implemented on a dSPACE Micro Autobox on the actual engine. The Proportional Derivative Integral (PID) controller
parameters obtained from the model were found to match fairly well with the experimental values, indicating the usefulness
of the developed idle speed model. Finally, the optimized idle speed control algorithm was embedded in and successfully demonstrated
with an in-house built, low cost engine management system (EMS) specifically designed for two-wheeler applications. 相似文献
650.
This paper describes an optimal vehicle speed controller that uses torque-based control concepts. The controller design was
divided into two steps: first, for a given vehicle speed trajectory, the engine torque demand was determined; in the second
stage, a torque controller was implemented to track this torque demand. The torque demand was determined by a primary component
and a correction component. The primary component was determined by solving an off-line optimization problem, and the correction
component was added to compensate for the error caused by the off-line optimization. A modelbased proportional-integral (PI)
feedback torque controller was employed to realize the engine torque tracking. Simulation results generated by a benchmark
simulator were given to demonstrate performance of the optimal vehicle speed controller and a conventional PI speed controller
that was included for comparison. 相似文献