The effect of external non-driving factors,payment type and waiting and queuing on fatigue in long distance trucking

Introduction

The aim of this study was to explore the effects of external influences on long distance trucking, in particular, incentive-based remuneration systems and the need to wait or queue to load or unload on driver experiences of fatigue.

Methods

Long distance truck drivers (n = 475) were recruited at truck rest stops on the major transport corridors within New South Wales, Australia and asked to complete a survey by self-administration or interview. The survey covered demographics, usual working arrangements, details of the last trip and safety outcomes including fatigue experiences.

Results

On average drivers’ last trip was over 2000 km and took 21.5 h to complete with an additional 6 h of non-driving work. Incentive payments were associated with longer working hours, greater distances driven and higher fatigue for more drivers. Drivers required to wait in queues did significantly more non-driving work and experienced fatigue more often than those who did not. Drivers who were not paid to wait did the longest trips with average weekly hours above the legal working hours limits, had the highest levels of fatigue and the highest levels of interference by work with family life. In contrast, drivers who were paid to wait did significantly less work with shorter usual hours and shorter last trips. Multivariate analysis showed that incentive-based payment and unpaid waiting in queues were significant predictors of driver fatigue.

Conclusions

The findings suggest that mandating payment of drivers for non-driving work including waiting would reduce the amount of non-driving work required for drivers and reduce weekly hours of work. In turn this would reduce driver fatigue and safety risk as well as enhancing the efficiency of the long distance road transport industry.     

Analysis of the transient response of an automatic dynamic balancer for eccentric rotors

This paper investigates the transient response of a dynamical system modelling an automatic dynamic balancing mechanism for eccentric rotors. By using recently developed computational techniques, pseudospectra of the linearisation of the system about an equilibrium are computed. This approach allows one to quantify which eigenvalues are most sensitive to perturbation. It is shown how the sensitivity of the eigenvalues directly influences the transient response. Furthermore, the effect which a variation of the damping coefficients has on the pseudospectra structure is considered. A transient growth due to the non-normality of the linearised system is shown to lead to an exponential decay or to a collapse back to the stable equilibrium; these effects are identified with the changes in the sensitivities of the eigenvalues under variation of the damping parameters. This provides a new insight into the full nonlinear system, in which qualitatively similar transient responses are shown to occur.     

Investigation of a multi-ball, automatic dynamic balancing mechanism for eccentric rotors

This paper concerns an analytical and experimental investigation into the dynamics of an automatic dynamic balancer (ADB) designed to quench vibration in eccentric rotors. This fundamentally nonlinear device incorporates several balancing masses that are free to rotate in a circumferentially mounted ball race. An earlier study into the steady state and transient response of the device with two balls is extended to the case of an arbitrary number of balls. Using bifurcation analysis allied to numerical simulation of a fully nonlinear model, the question is addressed of whether increasing the number of balls is advantageous. It is found that it is never possible to perfectly balance the device at rotation speeds comparable with or below the first natural, bending frequency of the rotor. When considering practical implementation of the device, a modification is suggested where individual balls are contained in separate arcs of the ball race, with rigid partitions separating each arc. Simulation results for a partitioned ADB are compared with those from an experimental rig. Close qualitative and quantitative match is found between the theory and the experiment, confirming that for sub-resonant rotation speeds, the ADB at best makes no difference to the imbalance, and can make things substantially worse. Further related configurations worthy of experimental and numerical investigation are proposed.     

Structural health monitoring using shaped sensors

This paper is concerned with distributed sensors to measure the response of beam and plate structures. The design of modal sensors for beam structures is well established. The design for plate structures with constant thickness sensors may be achieved by optimizing the shape of the sensor boundary, or by optimizing the effectiveness of the electrode. Most applications consider vibration control, but this paper is concerned with structural health monitoring, where the sensor output is made sensitive to changes in key stiffness parameters, for example in joints. The procedure is based on finite element models of the structures, and thus distributed transducers may be designed for arbitrary beam and plate structures. Simulated examples of a beam and a plate excited by a rotating machine are used to demonstrate the approach.     

Efficient robust design via Monte Carlo sample reweighting

A novel probabilistic method for the optimization of robust design problems is presented. The approach is based on an efficient variation of the Monte Carlo simulation method. By shifting most of the computational burden to outside of the optimization loop, optimum designs can be achieved efficiently and accurately. Furthermore by reweighting an initial set of samples the objective function and constraints become smooth functions of changes in the probability distribution of the parameters, rather than the stochastic functions obtained using a standard Monte Carlo method. The approach is demonstrated on a beam truss example, and the optimum designs are verified with regular Monte Carlo simulation. Copyright © 2006 John Wiley & Sons, Ltd.     

Characteristics of fatal motorcycle crashes into roadside safety barriers in Australia and New Zealand

This paper reports on the findings of a retrospective case series study of fatal motorcyclist–roadside barrier collisions. Cases were retrieved from the National Coroners Information System (NCIS), the coronial case files of Australian jurisdictions, and the Crash Analysis System (CAS) of the New Zealand Transport Agency. Seventy seven (77) motorcycle fatalities involving a roadside barrier in Australia and New Zealand were examined. The fatalities usually involved a single vehicle crash and young men. The roadside barriers predominantly involved were steel W-beams, typically on a bend in the horizontal alignment of the road. A majority of fatalities occurred on a weekend, during daylight hours, on clear days with dry road surface conditions indicating predominantly recreational riding. Speeding and driving with a blood alcohol level higher than the legal limit contributed to a significant number of these fatalities.     

基于模态柔度曲率的损伤检测方法

由于模态柔度对结构损伤的高灵敏性,各种基于模态柔度的检测指标在结构无损探伤NDE(Nondestructive Damage Evaluation)中应用较多,如模态柔度差、模态柔度改变率和均匀荷载面曲率差等。这些指标经应用验证都具有一定的有效性。在此基础上,采用模态柔度曲率的改变构建一种新的指标,称为模态柔度曲率差(MFC)。尽管均匀荷载面曲率差也采用曲率,但不同的是它先将模态柔度矩阵按行加起来,再求损伤前后的曲率差。而提出的模态柔度曲率差则按列计算损伤前后模态柔度矩阵的曲率差,然后挑选每列里面最大的值作为指标。采用一个简支梁和一个四跨连续梁为算例,考虑各种损伤情况,将该指标与模态柔度差、模态柔度改变率和均匀荷载面曲率差、以及振型曲率改变率等指标进行了比较,证明了模态柔度曲率差检测损伤的有效性和优越性。