Driving situations and driver decisions at road traffic signals

Driver performance in responding to the green-amber-red signal change was studied based on a sample of 2316 last crossing and first stopping vehicles collected by unobtrusive observations at 10 junction approaches in Singapore. Two schemes, a speed-distance diagram (S-D) and an acceleration-deceleration (A-D) diagram, were used to demarcate the driving situations; the driver actions, as revealed outcomes of driver decision-making, were mapped onto these diagrams. The speed-distance diagram can give some indication on what a driver would possibly do. The more complicated acceleration-deceleration diagram is useful for diagnosing the appropriateness of the driver actions. An application of the A-D diagram was demonstrated, and several situations prone to red-running were noted.     

篮球巨人新形象

01.Oliver Peoples眼镜姚明的外形是属于满有个性的种类,如何将篮球场上的高昂战意转化成圆融的商场智慧是一项新挑战。架上一副来自美国好莱坞品牌Oliver Peoples的眼镜,就马上能增添几分温文尔雅和书卷气了。     

Multi-commodity traffic assignment by continuum approximation of network flow with variable demand

Consider a city with several highly compact central business districts (CBD), and the commuters’ destinations from each of them are dispersed over the whole city. Since at a particular location inside the city the traffic movements from different CBDs share the same space and do not cancel out each other as in conventional fluid flow problems albeit travelling in different directions, the traffic flows from a CBD to the destinations over the city are considered as one commodity. The interaction of the traffic flows among different commodities is governed by a cost–flow relationship. The case of variable demand is considered. The primal formulation of the continuum equilibrium model is given and proved to satisfy the user optimal conditions, and the dual formulation of the problem and its complementary conditions are also discussed. A finite element method is then employed to solve the continuum problem. A numerical example is given to illustrate the effectiveness of the proposed method.     

Effects of intersection field of view on emergent collision avoidance performance at unsignalized intersections: analysis based on driving simulator experiments

Proper intersection sight distance can effectively lower the possibility of intersection accidents. American Association of State Highway and Transportation Officials (2011) provide a series of recommended dimensions of intersection sight triangles for uncontrolled and stop/yield‐controlled intersections. However, in reality, although the actual intersection design for unsignalized intersections satisfies the requirements of sight distance and clear sight triangle in American Association of State Highway and Transportation Officials' guideline, there are still a large number of crashes occurring at unsignalized intersections for drivers running stop/yield signs or failing to slow down. This paper presents a driving simulator study on pre‐crash at intersections under three intersection field of view (IFOV) conditions. The aim was to explore whether better IFOVs at unsignalized intersections improve their emergent collision avoidance performance under an assumption of valid intersection sight distance design. The experimental results show drivers' ability to identify potential hazards to be significantly affected by their IFOVs. As drivers' IFOV improved, drivers were more likely to choose braking actions to avoid collisions. Better IFOVs were also associated with significant increases in brake time to intersection and significant reductions in deceleration rate and crash rate, thus leading to a lower risk of traffic crash involvement. The results indicate that providing a better IFOV for drivers at intersections should be encouraged in practical applications in order to improve drivers' crash avoidance capabilities. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling and simulation of a dual-mode electrohydraulic fully variable valve train for four-stroke engines

In modern four-stroke automotive engine technology, variable valve timing and lift control offer potential benefits for making a high-performance engine. In this paper, a novel design named dual-mode electrohydraulic fully variable valve train (EHFVVT) for both engine intake and exhaust valves is introduced. The system is mainly controlled by either proportional flow control valves or proportional pressure relief valves, and hence two different families of valve displacement patterns can be achieved. The construction of the mathematical model of the valve train system and its dynamic analysis are also presented in this paper. Experimental and simulation results show that the dual-mode electrohydraulic variable valve train can achieve fully variable valve timing and lift control, and has the potential to eliminate the traditional throttle valve in the gasoline engines. With the proposed system, the engine performance at various speeds and loads will be significantly improved.     

Estimation of a time‐dependent origin‐destination matrix for congested highway networks

This paper presents a time‐dependent origin‐destination (O‐D) matrix estimation procedure embedded with a dynamic traffic assignment model, in which the predictive dynamic user optimal conditions in congested networks are maintained. Two solution algorithms are proposed, namely: an iterative (ITR) scheme and a method of successive averages (MSA) scheme. It is found that the MSA scheme outperforms the ITR scheme. As a prior O‐D matrix is an important input for the problem, its quality is essential for the reliability of the matrix estimation procedure. Empirical constraints are set in relation to the quality of the prior O‐D matrix for the estimation procedure. Numerical examples are used to demonstrate the effectiveness of the proposed methodology.     

Impact behavior modeling of motorcycle front wheel-tire assembly

Experiments were conducted to investigate the influence of certain parameters that affect the impact response of the motorcycle front wheel-tire assembly under various impact conditions. Impact tests were conducted according to 2 _ν ^{5 − 1} fractional factorial design using a pendulum impact test apparatus with impact speed, impact mass, tire inflation pressure level, striker geometry, and impact location as design factors. Significant factors influencing the response of the wheel-tire assembly were identified. Coefficients for each factor were also determined, and empirical models were then developed for each response. An analysis indicates that the developed models fit well within the experimental ranges of the respective factors. However, for several interaction effects, the models become unrealistic, whereby they give certain deformation values when approaching zero impact mass and/or zero impact velocity. This is not consistent with the mechanics of the physical world, as there should not be any significant deformation when delivered impact energy is small enough. Efforts have been made in developing better models to resolve the inconsistency and to include a wider range, especially considering the case of the lower limit of experimental factors, which are an impact mass of 51.18 kg and/or an impact velocity of 3 m s⁻¹ (10.8 km/h) down to zero. The minimum amount of impact energy required to produce the onset of observable deformation on the wheel was incorporated in the development of new models. Finally, the present models have been developed not only to cover the lower regions but also to range up to the upper limits of the factors, which are an impact mass of 101.33 kg and an impact velocity of 6 m s⁻¹ (21.6 km/h).