Driver sensitivity to brake pulse duration and magnitude

Adaptive cruise control (ACC) requires that the driver intervene in situations that exceed the capability of ACC. A brake pulse might provide a particularly compatible means of alerting the driver to situations in which the acceleration authority of the ACC has been exceeded. This study examined the sensitivity of the driver to brake pulses of five different amplitudes (0.01-0.025 g) and five different durations (50-800 ms). Drivers were sensitive to accelerations as low as 0.015 g. Pulse duration interacted with pulse amplitude, such that moderate duration pulses were more detectable than long and short duration pulses at intermediate levels of pulse amplitude. A power function with an exponent of 1.0 accounted for 99% of the variance in drivers' sensitivity to pulse amplitude; however, a power function with an exponent of 0.23 accounted for only 70% of the variance in drivers' sensitivity to pulse duration. These results can help designers create ACC algorithms and develop brake pulse warnings.     

Relationships between driving simulator performance and driving test results

This article is considered relevant because: 1) car driving is an everyday and safety-critical task; 2) simulators are used to an increasing extent for driver training (related topics: training, virtual reality, human – machine interaction); 3) the article addresses relationships between performance in the simulator and driving test results–a relevant topic for those involved in driver training and the virtual reality industries; 4) this article provides new insights about individual differences in young drivers' behaviour. Simulators are being used to an increasing extent for driver training, allowing for the possibility of collecting objective data on driver proficiency under standardised conditions. However, relatively little is known about how learner drivers' simulator measures relate to on-road driving. This study proposes a theoretical framework that quantifies driver proficiency in terms of speed of task execution, violations and errors. This study investigated the relationships between these three measures of learner drivers' (n = 804) proficiency during initial simulation-based training and the result of the driving test on the road, occurring an average of 6 months later. A higher chance of passing the driving test the first time was associated with making fewer steering errors on the simulator and could be predicted in regression analysis with a correlation of 0.18. Additionally, in accordance with the theoretical framework, a shorter duration of on-road training corresponded with faster task execution, fewer violations and fewer steering errors (predictive correlation 0.45). It is recommended that researchers conduct more large-scale studies into the reliability and validity of simulator measures and on-road driving tests.     

How do environmental characteristics at intersections change in their relevance for drivers before entering an intersection: analysis of drivers’ gaze and driving behavior in a driving simulator study

Accident studies in Germany found that in about 90 % of intersection accidents, failure to acquire the relevant information of the driving situation was the main reason for drivers’ errors (Vollrath et al. in Ableitung von Anforderungen an Fahrerassistenzsysteme aus Sicht der Verkehrssicherheit. Wirtschaftsverlag NW, Bremerhaven, 2006). Studies of bicycle–car accidents assume that improper attention allocation strategies and unjustified expectations by drivers are important for this kind of error (Räsänen and Summala in Accid Anal Prev 30:657–666, 1998). Aim of the study was to examine the psychological processes of drivers’ attention allocation and driving behavior in different intersection situations varied by two environmental characteristics. A give way T-intersection was varied by (1) low and high traffic density of oncoming cars from the left and (2) number of task-relevant information areas (in addition to the oncoming cars from the left with or without pedestrians on the right). It was examined how these environmental characteristics change in their relevance for drivers while entering the intersections. The analysis was conducted in three intersection epochs (Approaching, Waiting, Accelerating). A total of 40 subjects (26 male, 14 female), ranged in age from 19 to 55 years (M = 31.0 years), participated in the study. The results showed that drivers’ attention allocation (e.g., mean gaze duration) and driving behavior (e.g., waiting time) systematically depends on these environmental characteristics which require different actions of the driver and change in their relevance when entering an intersection. The results support the idea of attention allocation strategies by drivers which are specific for certain driving situations. These findings can support approaches of driver modeling at intersections.     

Microthermal sensors for determining fluid composition and flow rate in fluidic systems

To analyze fluid mixtures a simple and low cost measurement method is realized using a microthermal sensor that introduces a short heat pulse into the fluid under test whilst the resulting temperature increase reflects thermal parameters of the fluid. For methanol in water this principle showed an almost linear dependence of the temperature increase on the methanol content for the volume concentration range 0–20 %. The sensitivity was determined to S = 0.19 K/(% (V/V)) for a heat pulse of 0.5 s duration and a heater power of 30 mW. The accuracy achieved in stopped-flow single pulse measurements is ~0.5 % (V/V). By integrating additional temperature sensors in front and behind the microheater the flow rate of the liquid can also be determined using thermal anemometry. The low cost sensor construction and simple signal analysis make this principle promising for use in low cost mobile applications like DMFC power supplies for laptops.     

Cognitive control by brain-injured car drivers: an exploratory study

Cognitive control is a key tool for adaptation in dynamic situations. The aim of the study is to assess the relevance of a theoretical framework for cognitive control in dynamic situations, in order to understand brain-injured (BI) car drivers' cognitive impairment. The framework supports a cognitive control multimodality based on the crossing of two orthogonal dimensions: symbolic/subsymbolic; anticipative/reactive control. BI car drivers' behaviour was compared with that of a control group (CTRL) during driving simulator scenarios. Eye movement analysis, among other variables, revealed that BI car drivers made use of a more symbolic and reactive control than did CTRL drivers. CTRL drivers showed a more stable cognitive compromise than BI drivers. The latter became less symbolic and more reactive in the case of difficult scenarios. In addition, BI drivers focused on the main task of trajectory management, with fewer resources devoted to traffic interaction management.

Statement of Relevance:An explanation of differences between BI and CTRL drivers in terms of cognitive control requirements, attention and processing speed is put forward. From this, it is possible to derive some implications in terms of driver assistance (e.g. lane keeping or a warning assistance device) and rehabilitation.     

Human Factors Assessment of Vehicle Power Steering

Abstract

The handling and steering of an in-service wheeled vehicle were investigated, following a number of adverse reports. This paper presents the subjective assessments of the vehicle's power steering, which were included in that investigation.

The effects of three different power steering settings were appraised by driving the vehicles on a road-test track and cross-country. In addition, two questionnaires enabled the drivers' overall views and comments on specific factors to be recorded. Analysis of variance showed that the subjectively assessed differences between the three vehicle power steering settings were statistically significant at the 2 per cent level. The six civilian and six military drivers' views were congruent and course differences (road or cross-country) did not consistently and significantly affect the overall assessment. The drivers' stated preferences among the vehicles supported the analysis of variance results.

Incidents observed during the trials showed that drivers could lose control of the vehicle because of excessive speed and/or faulty driving technique, independently of power steering characteristics. This suggests that many incidents could be prevented by giving specific instructional guidelines to drivers during training and by the incorporation of a speed limiting device in any modifications to the vehicle tested.     

Auditory alerts for in-vehicle information systems: The effects of temporal conflict and sound parameters on driver attitudes and performance

In-vehicle information systems will soon confront drivers with an increasing number of warnings and alerts for situations ranging from imminent collisions to the arrival of e-mail messages. Coordinating these alerts can ensure that they enhance rather than degrade driving safety. Two experiments examined how temporal conflict and sound parameters affect driver performance and acceptance. The temporal conflict of an e-mail alert occurring 300?ms before a collision warning interfered with the response to the collision warning, but an e-mail alert occurring 1000?ms before the collision warning had the opposite effect and enhanced the response to the collision warning. These results emphasize the need to consider how in-vehicle devices influence drivers' strategic anticipation of high-demand situations. Regarding sound parameters, results showed that highly urgent sounds tended to speed drivers' accelerator release, but the annoyance associated with highly urgent sounds increased workload. In fact, there was a strong positive association between ratings of annoyance and subjective workload. Consistent with the urgency mapping principle, there was a slight negative association between the differences in the rated urgency of collision warnings and e-mail alerts and subjective workload. The results suggest that warning and alert design should consider an annoyance trade-off in addition to urgency mapping.     

Three‐dimensional analysis of a driver‐passenger vehicle interface

This article presents a method of analyzing how drivers' anthropometric data are best accommodated by a specific driver‐vehicle interface. Three‐dimensional (3‐D) manikins with 18 links were developed using anthropometric data for the U.S. 95th percentile male and 5th percentile female. In addition, an adjustable seating buck was constructed to control 7 package variables. After the manikins were positioned in each driving environment, 3‐D Cartesian coordinates for the manikins' articulations were determined using a coordinate measuring machine. The data were then converted into joint angles to suggest suitable driving environments that consider appropriate driving postures. © 2004 Wiley Periodicals, Inc. Hum Factors Man 14: 269–284, 2004.     

基于模糊综合评价的疲劳驾驶检测算法研究

疲劳驾驶是引发交通事故的一个主要原因，对驾驶员疲劳驾驶做出准确、有效的检测和预防，具有重要的社会意义.在研究比较了前人工作的基础上，设计了一种基于机器视觉，图像处理的驾驶员疲劳检测机制.首先将传来的连续帧图像（视频）利用Adaboost算法进行人脸检测，根据人脸"三庭五眼"的分布特征分割出大致的人眼区域.在人眼定位过程中，采用OSTU阈值分割，非线性点运算和积分投影等预处理消除眉毛，并利用模糊综合评价算法对眼睛矩形区域的长宽比、拟合椭圆面积、瞳孔黑色素所占比例这3个影响因子进行分析，判别出眼睛的睁开闭合状态.最后根据PERCLOS原理对驾驶员的疲劳状态做出检测.实验结果表明，所提算法能够准确地判别出眼睛的睁闭状态及对驾驶员的疲劳状态的检测，具有较高的准确性和实用性.     

Manufacture of microfluidic glass chips by deep plasma etching, femtosecond laser ablation, and anodic bonding

Two dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C₄F₈/O₂) using an electroplated Ni mask. Depth up to 100 μm with a profile angle of 83°–88° and a smooth bottom of the etched structure (Ra below 3 nm) were achieved at an etch rate of 0.9 μm/min. An ultrashort pulse Ti:sapphire laser operating at the wavelength of 800 nm and 5 kHz repetition rate was used for micromachining. Channels of 100 μm width and 140 μm height with a profile angle of 80–85° were obtained in 3 min using an average power of 160 mW and a pulse duration of 120 fs. A novel process for glass–glass anodic bonding using a conductive interlayer of Si/Al/Si has been developed to seal microfluidic components with good optical transparency using a relatively low temperature (350°C).     

Situation awareness assessment in critical driving situations at intersections by task and human error analysis

The rapid development of sensor and tracking technology enables deployment of new Advanced Driver Assistance Systems (ADAS) that support the driver not just on highways but in urban areas as well. Intersections particularly present critical traffic scenarios where almost 35% of accidents occur, partially due to the present lack of in‐depth research about human errors and their determinants. The first step in ergonomic design of ADAS is to identify the specific situations in which drivers require support. To contribute to identification of such spots, situation awareness of 20 drivers in four critical intersection scenarios was explored. The study was conducted in the fixed‐base driving simulator. The applied approach consisted of assessing drivers' expectations and mental workload and of comparing theoretically correct cognitive behavior to experimentally collected data. Intersection scenarios were divided into five segments, and for each segment a task analysis was made. The study has shown that the driving simulator environment can be successfully deployed to provoke and explore various driver errors. The results have revealed that, in scenarios in which information is objectively missing, the majority of errors happened because the drivers had inaccurate mental models of particular scenarios. To the contrary, in the complex scenario the major cause of accidents was information overload. Furthermore, the task analysis disclosed applicable areas of intersection assistance. © 2010 Wiley Periodicals, Inc.     

The effect of communicational signals on drivers' subjective appraisal and visual attention during interactive driving scenarios

Communicational signals (e.g. lights and horns) are imperative for on-road interaction between drivers. The aim of the present study was to explore how these signals affect drivers' subjective appraisal and visual attention, and how drivers decode the signals from other vehicles within a variety of interactive contexts. Twenty-five male participants (20 valid samples, ranging from 21 to 29 years of age) were recruited to watch film clips of pre-designed interactive scenarios involving common vehicle signals in a full-view simulator (i.e. including road view and mirror views). Participants' attitudes towards the interacting vehicle's behaviours, emotional responses, fixation metrics, and decoded meanings were recorded and analysed. The majority of tested signals, with the exception of the horn used in the behind vehicles, significantly improved drivers' attitudes and pleasure. All signals significantly increased emotional arousal, as well as the total fixation time and mean fixation duration on the interacting vehicle. When the interacting vehicle was visible in mirrors, the signal usage significantly increased the fixation frequency towards it. Meanwhile, a significant decrease in total fixation time and mean fixation duration on the road was reported. The results also demonstrated that the decoded signal contained several meanings simultaneously depending on both the signal type and its interactive context. This study quantified the communication process via vehicular signals under typical situations involving other vehicles, and also suggested new ideas on how to establish more advanced communication between drivers.     

基于大规模GPS轨迹数据的出租车换道行为研究

出租车换道行为的统计特性对研究经济、心理等人类动力学有重要的意义.结合大数据分析技术,基于西安市出租车GPS轨迹数据对出租车司机的换道行为进行了定量研究.设计了一种基于出租车GPS轨迹数据的出租车司机换道行为识别模型,利用大数据平台对出租车司机换道次数按不同时段进行了定量统计,对出租车司机换道次数、出租车平均行驶速度和出租车司机的收入之间进行了相关性分析.分析结果表明,出租车频繁换道行为对司机收益呈现负相关影响,进一步说明出租车司机驾驶习惯和和心理对整个出租车运营有显著影响.     

考虑差异化需求的电动汽车充电调度策略

电动汽车行驶里程短、充电时间长是影响驾驶体验的关键.通过对电网、充电设备进行大规模升级的方法减少充电时间,成本昂贵,因此充分利用现有路网、电网资源,制定智能充电调度策略成为提高驾驶体验的重要手段.考虑到驾驶者对充电时间敏感度的异质性,提出具有差异化的调度策略以满足不同优先级驾驶者的需求.首先,为均衡不同优先级驾驶者的利益,提出一种基于动态截断机制的两优先级队列模型;其次,定义充电站的准入原则,保证高优先级驾驶者对预留桩的使用权及对空闲桩的优先抢占权;然后,提出基于截断机制的双层优化模型CCPQ(charging with cut-off priority queue),在顶层高优先级车辆与充电桩最优匹配的基础上,设计底层低优先级车辆的分配策略优化模型,将最小化低优先级驾驶者的总等待时间构建为凸优化问题;最后,通过仿真验证策略的有效性及优越性.     

Effects of menu structure and touch screen scrolling style on the variability of glance durations during in-vehicle visual search tasks

The effects of alternative navigation device display features on drivers' visual sampling efficiency while searching forpoints of interest were studied in two driving simulation experiments with 40 participants. Given that the number of display items was sufficient, display features that facilitate resumption of visual search following interruptions were expected to lead to more consistent in-vehicle glance durations. As predicted, compared with a grid-style menu, searching information in a list-style menu while driving led to smaller variance in durations of in-vehicle glances, in particular with nine item displays. Kinetic touch screen scrolling induced a greater number of very short in-vehicle glances than scrolling with arrow buttons. The touch screen functionality did not significantly diminish the negative effects of the grid-menu compared with physical controls with list-style menus. The findings suggest that resumability of self-paced, in-vehicle visual search tasks could be assessed with the measures of variance of in-vehicle glance duration distributions.

Statement of Relevance: The reported research reveals display design factors affecting safety-relevant variability of in-vehicle glance durations and provides a theoretical framework for explaining the effects. The research can have a significant methodical value for driver distraction research and practical value for the design and testing of in-vehicle user interfaces.     

Ted Megaw: an appreciation

Driver workspace design and evaluation is, in part, based on assumed driving postures of users and determines several ergonomic aspects of a vehicle, such as reach, visibility and postural comfort. Accurately predicting and specifying standard driving postures, hence, are necessary to improve the ergonomic quality of the driver workspace. In this study, a statistical clustering approach was employed to reduce driving posture simulation/prediction errors, assuming that drivers use several distinct postural strategies when interacting with automobiles. 2-D driving postures, described by 16 joint angles, were obtained from 38 participants with diverse demographics (age, gender) and anthropometrics (stature, body mass) and in two vehicle classes (sedans and SUVs). Based on the proximity of joint angle sets, cluster analysis yielded three predominant postural strategies in each vehicle class (i.e. ‘lower limb flexed’, ‘upper limb flexed’ and ‘extended’). Mean angular differences between clusters ranged from 3.8 to 52.4° for the majority of joints, supporting the practical relevance of the distinct clusters. The existence of such postural strategies should be considered when utilising digital human models (DHMs) to enhance and evaluate driver workspace design ergonomically and proactively.

Statement of Relevance: This study identified drivers' distinct postural strategies, based on actual drivers' behaviours. Such strategies can facilitate accurate positioning of DHMs and hence help design ergonomic driver workspaces.     

The ability of eye-tracking metrics to classify and predict the perceived driving workload

Traffic safety is directly related to the mental and physical condition of the driver. Performing regular secondary tasks while driving is an additional activity that dissipates attention and adds to the drivers' workload. Identifying driver fatigue and workload based on gaze behavior is one way to ensure a safe driving experience. The purpose of this paper is to classify and predict driving perceived workload using a set of eye-tracking metrics (gaze fixation, duration, pointing, and pupil diameter). The ability of eye-tracking metrics to predict driving workload has been investigated. As a result, frustration, performance, and temporal load showed a correlation with gaze metrics. Gaze point, duration, fixation, and pupil diameter significantly influence driving workload.Relevance to industry: Results will supply the specialists in eye-tracking/sensor technologies and traffic safety with new knowledge to improve the design of the driving performance and safety monitoring systems and efficiency of the driving process.     

一种软启停正负双直流电源的设计

变形镜驱动器正负电源加电或者断电不同步,导致其在加电瞬间或者断电瞬间,输出端会输出一个-38.0V和86.0V的冲击电压,这个冲击电压使得变形镜在未开始工作时就产生了较为严重的面形畸变,为此研制了基于微处理器的软启停直流电源,它输出两路按一定时序变化的输出电压作为后续两个继电器的控制端,再通过这两个继电器分别控制变形镜驱动器正、负电源的导断,从而使得变形镜驱动器的正负电源同时加载或者卸载。在硬件平台了进行了实验验证,结果表明,使用软启停直流电源后,变形镜驱动器加电瞬间或断电瞬间,其产生的脉冲电压的峰-峰不超过0.45V,远远小于未使用软启停直流电源前的冲击电压,满足了系统的设计要求。     

The role of psychological factors in workplace safety

Workplace safety researchers and practitioners generally agree that it is necessary to understand the psychological factors that influence people's workplace safety behaviour. Yet, the search for reliable individual differences regarding psychological factors associated with workplace safety has lead to sparse results and inconclusive findings. The aim of this study was to investigate whether there are differences between the psychological factors, cognitive ability, personality and work-wellness of employees involved in workplace incidents and accidents and/or driver vehicle accidents and those who are not. The study population (N = 279) consisted of employees employed at an electricity supply organisation in South Africa. Mann–Whitney U-test and one-way ANOVA were conducted to determine the differences in the respective psychological factors between the groups. These results showed that cognitive ability did not seem to play a role in workplace incident/accident involvement, including driver vehicle accidents, while the wellness factors burnout and sense of coherence, as well as certain personality traits, namely conscientiousness, pragmatic and gregariousness play a statistically significant role in individuals' involvement in workplace incidents/accidents/driver vehicle accidents. Safety practitioners, managers and human resource specialists should take cognisance of the role of specifically work-wellness in workplace safety behaviour, as management can influence these negative states that are often caused by continuously stressful situations, and subsequently enhance work place safety.     

Effect of button location on driver's visual behaviour and safety perception

Although buttons are a frequently used type of control in car interiors, little research has been undertaken on how the usage of buttons affects the visual behaviour of the driver. In this study, the aim was to analyse the effect of push button location and auditory feedback on drivers' visual time off road and safety perception when driving in a real traffic situation. The effect of six button locations (five on the centre stack, one near the gear stick) was tested. Drivers' visual behaviour was studied in real traffic on a motorway. An eye tracking system recorded the visual behaviour of eight drivers who, in 96 repeated trials each, were instructed to press a specific button. Data analysis focused on the drivers' visual time off road and safety perception in relation to the location of the button to be pressed. Auditory feedback did not show a significant effect on visual time off road. The time off road increased significantly as the angle increased between the normal line of sight and button location for the five buttons placed on the centre stack. Results for the button located close to the gear stick, with the highest eccentricity, produced a short time off road. This unexpected finding is discussed in terms of three potential explanations: 1) the role of perceptual discrimination; 2) risk perception; and 3) motor control.