Driver behavior during bicycle passing maneuvers in response to a Share the Road sign treatment

The interaction of motorists and bicyclists, particularly during passing maneuvers, is an area of concern to the bicycle safety community as there is a general perception that motor vehicle drivers may not share the road effectively with bicyclists. This is a particular concern on road sections with centerline rumble strips where motorists are prone to crowd bicyclists during passing events. One potential countermeasure to address this concern is the use of a bicycle warning sign with a “Share the Road” plaque. This paper presents the results of a controlled field evaluation of this sign treatment, which involved an examination of driver behavior while overtaking bicyclists. A series of field studies were conducted concurrently on two segments of a high-speed, rural two-lane highway. These segments were similar in terms of roadway geometry, traffic volumes, and other relevant factors, except that one of the segments included centerline rumble strips while the other did not. A before-and-after study design was utilized to examine changes in motor vehicle lateral placement and speed at the time of the passing event as they relate to the presence of centerline rumble strips and the sign treatment. Centerline rumble strips generally shifted vehicles closer to the bicyclists during passing maneuvers, though the magnitude of this effect was marginal. The sign treatment was found to shift motor vehicles away from the rightmost lane positions, though the signs did not significantly affect the mean buffer distance between the bicyclists and passing motorists or the propensity of crowding events during passing. The sign treatment also resulted in a 2.5 miles/h (4.0 km/h) reduction in vehicle speeds. Vehicle type, bicyclist position, and the presence of opposing traffic were also found to affect lateral placement and speed selection during passing maneuvers.     

Driver responses to differing urban work zone configurations

This study reports the results of a simulator-based assessment of driver response to two different urban highway work zone configurations. One configuration represented an existing design which was contrasted with a second configuration that presented a reduced taper length prototype work zone design. Twenty-one drivers navigated the two different work zones in two different conditions, one with and one without a lead vehicle; in this case a bus. Measures of driver speed, braking, travel path, and collision frequency were recorded. Drivers navigated significantly closer to the boundary of the work area in the reduced taper length design. This proximity effect was moderated by the significant interaction between lead vehicle and taper length and such interactive effects were also observed for driver speed at the end of the work zone and the number of collisions observed within the work zone itself. These results suggest that reduced taper length poses an increase in risk to both drivers and work zone personnel, primarily when driver anticipation is reduced by foreshortened viewing distances. Increase in such risk is to a degree offset by the reduction of overall exposure to the work zone that a foreshortened taper creates. The benefits and limitations to a simulation-based approach to the assessment and prediction of driver behavior in different work zone configurations are also discussed.     

Driver experience and cognitive workload in different traffic environments

How do levels of cognitive workload differ between experienced and inexperienced drivers? In this study we explored cognitive workload and driver experience, using a secondary task method, the peripheral detection task (PDT) in a field study. The main results showed a large and statistically significant difference in cognitive workload levels between experienced and inexperienced drivers. Inexperienced, low mileage drivers had on average approximately 250 milliseconds (ms) longer reaction times to a peripheral stimulus, than the experienced drivers. It would, therefore, appear that drivers with better training and experience were able to automate the driving task more effectively than their less experienced counterparts in accordance with theoretical psychological models. It has been suggested that increased training and experience may provide attention resource savings that can benefit the driver in handling new or unexpected traffic situations.     

The effect of cell phone type on drivers subjective workload during concurrent driving and conversing

The effect of three types of cell phones (hand held, hands free with an external speaker and personal hands free) on total subjective workload (including its constituent components; mental demand, physical demand, temporal demand, performance, effort and frustration) and intelligibility was measured using the NASA-task load index (TLX) and the modified rhyme test (MRT), respectively in 13 experienced drivers (nine male, four female, age range 28-65 years), whilst driving on a rural highway. The drivers rated all components of workload for each type of cell phone to be significantly higher than for a control condition in which no cell phone was used. The mean (standard deviation) total workload was lowest for the personal hands free cell phone (7.1(3.65)) and highest for the hands free speaker phone (10.8 (3.63)) (P<0.001). The mean (standard deviation) intelligibility score was highest for the personal hands free cell phone (74.1 (7.9)) and lowest for the hands free speaker phone (55.0 (10.4)) (P<0.001). Frustration was significantly correlated with total workload (0.60, P<0.001) and intelligibility was significantly correlated with frustration (-0.35, P<0.05). Physical demand was not a high contributor to total workload. It is concluded that a personal hands free cell phone would interfere least with the cognitive demands of driving.     

Mental workload when driving in a simulator: Effects of age and driving complexity

Driving errors for older drivers may result from a higher momentary mental workload resulting from complex driving situations, such as intersections. The present study examined if the mental workload of young and older active drivers vary with the difficulty of the driving context. We adopted the probe reaction time (RT) technique to measure the workload while driving in a simulator. The technique provided clear instructions about the primary (driving) and secondary (RT) tasks. To avoid structural interference, the secondary task consisted of responding as rapidly as possible with a vocal response (“top”) to an auditory stimulus. Participants drove through a continuous 26.4-km scenario including rural and urban sections and probes (stimuli) were given in a baseline static condition and in three different driving contexts embedded into the overall driving scenario. Specifically, stimuli were given randomly when (a) driving on straight roads at a constant speed, (b) approaching intersections for which the driver had to stop the car, and (c) when overtaking a slower vehicle. Unless a driving error was made, drivers did not need any emergency responses. Reaction time was defined as the temporal interval between the auditory stimulus and the onset of the corresponding verbal response detected from the analog signal of a piezo-electric microphone fixed on a headset (ms accuracy). Baseline RTs were similar for both groups. Both groups showed longer RTs when driving and RTs increased as the complexity of the driving contexts increased (driving straights, intersections, overtaking maneuvers). Compared to younger drivers, however, older drivers showed longer RTs for all driving contexts and the most complex driving context (overtaking maneuvers) yielded a disproportionate increase. In conclusion, driving leads to a greater mental workload for the older drivers than for the younger drivers and this effect was exacerbated by the more complex driving context (overtaking maneuvers).     

Monitoring drivers’ mental workload in driving simulators using physiological measures

Many traffic accidents are caused by, or at least related to, inadequate mental workload, when it is either too low (vigilance) or too high (stress). Creating variations in mental workload and accident-prone driving for research purposes is difficult in the real world. In driving simulators the measurement of driver mental workload is relatively easily conducted by means of physiological measures, although good research skills are required and it is time-consuming. The fact that modern driving simulator environments are laboratory-equivalent nowadays allows full control with respect to environmental conditions, scenarios and stimuli, and enables physiological measurement of parameters of mental workload such as heart rate and brain activity. Several examples are presented to illustrate the potential of modern high-standard driving simulator environments regarding the monitoring of drivers’ mental workload during task performance.     

How do drivers behave during indecision zone maneuvers?

Yellow signal indications at intersections are well-known to be a contributor to traffic crashes. This study examined drivers’ behavior during yellow signal indication (i.e., indecision zone) maneuvers. Data from a driving simulator study was used, which included drivers’ performance data when they encountered a yellow signal indication at intersections under different secondary-task conditions. This study calculated drivers’ likelihood to go through a yellow signal indication and examined factors that are related to drivers’ decision making on intersection traversing. The results showed that drivers’ decision on stopping or not at a yellow signal indication was associated with different variables including age, distraction, pedal conditions, and time to stop line. Distracted drivers’ insensitive behavior was also captured from the significant interaction effect between time to stop line and distraction conditions, which implied that intersection related crash risk may increase when drivers were distracted.     

The effects of age and workload on 3D spatial attention in dual-task driving

In the present study we assessed whether the limits in visual–spatial attention associated with aging affect the spatial extent of attention in depth during driving performance. Drivers in the present study performed a car-following and light-detection task. To assess the extent of visual–spatial attention, we compared reaction times and accuracy to light change targets that varied in horizontal position and depth location. In addition, because workload has been identified as a factor that can change the horizontal and vertical extent of attention, we tested whether variability of the lead car speed influenced the extent of spatial attention for younger or older drivers. For younger drivers, reaction time (RT) to light-change targets varied as a function of distance and horizontal position. For older drivers RT varied only as a function of distance. There was a distance by horizontal position interaction for younger drivers but not for older drivers. Specifically, there was no effect of horizontal position at any given level of depth for older drivers. However, for younger drivers there was an effect of horizontal position for targets further in depth but not for targets nearer in depth. With regards to workload, we found no statistically reliable evidence that variability of the lead car speed had an effect on the spatial extent of attention for younger or older drivers. In a control experiment, we examined the effects of depth on light detection when the projected size and position of the targets was constant. Consistent with our previous results, we found that drivers’ reaction time to light-change targets varied as a function of distance even when 2D position and size were controlled. Given that depth is an important dimension in driving performance, an important issue for assessing driving safety is to consider the limits of attention in the depth dimension. Therefore, we suggest that future research should consider the importance of depth as a dimension of spatial attention in relation to the assessment of driving performance.     

Simulator sickness during driving simulation studies

While driving simulators are a valuable tool for assessing multiple dimensions of driving performance under relatively safe conditions, researchers and practitioners must be prepared for participants that suffer from simulator sickness. This paper describes multiple theories of motion sickness and presents a method for assessing and reacting to simulator sickness symptoms. Results showed that this method identified individuals who were unable to complete a driving simulator study due to simulator sickness with greater than 90% accuracy and that older participants had a greater likelihood of simulator sickness than younger participants. Possible explanations for increased symptoms experienced by older participants are discussed as well as implications for research ethics and simulator sickness prevention.     

A method to assess the driver mental workload: The driving activity load index (DALI)

Intelligent transport system (ITS) can induce improvement in road safety, as long as acceptability by user?s population and adequacy with driving task demands have been checked. The Human-Centred Design process allows taking into account the diversified driver?s population needs and functional abilities in addition to the complexity of the driving context, for setting up design recommendations and for the development of methodologies for safety assessment. Evaluation of the driver?s mental workload is an important parameter, complementary to objective ones such as control of the vehicle and driver?s visual strategies. This paper describes experiments conducted in the framework of the European project AIDE aiming at validating the DALI (Driving Activity Load Index), a tool set up to allow the evaluation of driver?s mental workload while driving, with or without the support of in-vehicle systems. The main results and conclusion from the conducted analysis are presented.     

A simulator study on the impact of traffic calming measures in urban areas on driving behavior and workload

This study examined the impact of traffic calming measures (TCM) on major roads in rural and urban areas. More specifically we investigated the effect of gate constructions located at the entrance of the urban area and horizontal curves within the urban area on driving behavior and workload. Forty-six participants completed a 34 km test-drive on a driving simulator with eight thoroughfare configurations, i.e., 2 (curves: present, absent) × 2 (gates: present, absent) × 2 (peripheral detection task (PDT): present, absent) in a within-subject design.     

The Driver Prioritisation Questionnaire: Exploring drivers’ self-report visual priorities in a range of driving scenarios

Previous research has noted that novice drivers are at greatest risk of an accident. One reason that has been reported for this is that they have not developed the optimum visual search strategies of their more experienced counterparts. One might expect that new drivers might be taught the appropriate visual skills while learning to drive, though this requires instructors to have introspection into their own visual skills before they can be passed on to the student. In addition novice drivers should be able to acquire the instructed skills. This study used an image-based questionnaire to assess driving instructors’ and novice drivers’ priority ratings for attending to different areas of the driving scene across nine scenarios. It was predicted that if instructors and novices have introspection into the relative importance of these different areas, there should be agreement across the sample of participants. Additionally it was considered important to assess which areas of the visual scene are important across all different scenarios and which areas change in priority with a change in scenario. Results showed that for both groups the opinions regarding visual field prioritisation were highly consistent when compared to chance. Despite the rating consistencies, group differences were found, across all scenarios with “Rear View Mirrors” being the visual field with the most frequent observed group differences. Certain categories (“Road Ahead” and “Mirrors”) were highly ranked across all scenarios, while other categories were more scenario specific. We conclude that both groups have insight into some elements of visual search. However, in many occasions the prioritisation was different between driving instructors and novice drivers. It appears that during the learning process the novice drivers did not adopt the prioritisation strategies seen in driving instructors. This has important implications for the teaching of visual skills in driving.     

Do mental workload and presence experienced when driving a real car predispose drivers to simulator sickness? An exploratory study

This study is aimed at determining whether the simulator sickness (SS) experienced by some drivers is influenced by psychological factors, such as cognitive solicitation, affective factors and a feeling of presence. We also wished to determine whether SS is caused by an individual reaction to the virtual environment (VE) itself or can be attributed to a more general personal predisposition. For this reason, we considered three conditions: driving a simulator, driving one’s own vehicle and driving a school-owned vehicle. Fourteen expert drivers participated in the study. Each drove under a different experimental condition and then responded to various questionnaires (SSQ, NASA-TLX and QPF). Our results showed that it is possible to identify at least three sources of explanation of why some people are more liable to feel sick in a driving simulator.     

Driver distraction: the effects of concurrent in-vehicle tasks, road environment complexity and age on driving performance

This paper presents the findings of a simulator study that examined the effects of distraction upon driving performance for drivers in three age groups. There were two in-vehicle distracter tasks: operating the vehicle entertainment system and conducting a simulated hands-free mobile phone conversation. The effect of visual clutter was examined by requiring participants to drive in simple and complex road environments. Overall measures of driving performance were collected, together with responses to roadway hazards and subjective measures of driver perceived workload. The two in-vehicle distraction tasks degraded overall driving performance, degraded responses to hazards and increased subjective workload. The performance decrements that occurred as a result of in-vehicle distraction were observed in both the simple and complex highway environments and for drivers in different age groups. One key difference was that older drivers traveled at lower mean speeds in the complex highway environment compared with younger drivers. The conclusions of the research are that both in-vehicle tasks impaired several aspects of driving performance, with the entertainment system distracter having the greatest negative impact on performance, and that these findings were relatively stable across different driver age groups and different environmental complexities.     

Event-related potentials and secondary task performance during simulated driving

Inattention and distraction account for a substantial number of traffic accidents. Therefore, we examined the impact of secondary task performance (an auditory oddball task) on a primary driving task (lane keeping). Twenty healthy participants performed two 20-min tests in the Divided Attention Steering Simulator (DASS). The visual secondary task of the DASS was replaced by an auditory oddball task to allow recording of brain activity. The driving task and the secondary (distracting) oddball task were presented in isolation and simultaneously, to assess their mutual interference. In addition to performance measures (lane keeping in the primary driving task and reaction speed in the secondary oddball task), brain activity, i.e. event-related potentials (ERPs), was recorded. Performance parameters on the driving test and the secondary oddball task did not differ between performance in isolation and simultaneous performance. However, when both tasks were performed simultaneously, reaction time variability increased in the secondary oddball task. Analysis of brain activity indicated that ERP amplitude (P3a amplitude) related to the secondary task, was significantly reduced when the task was performed simultaneously with the driving test. This study shows that when performing a simple secondary task during driving, performance of the driving task and this secondary task are both unaffected. However, analysis of brain activity shows reduced cortical processing of irrelevant, potentially distracting stimuli from the secondary task during driving.     

Driver behaviour during flashing green before amber: a comparative study

The paper discusses the results of extensive measurements of drivers' stopping behaviour during signal programmes with and without flashing green before amber. Ten locations in Switzerland, Austria, and Germany were recorded with a video camera and analysed using an image-processing system. About 5000 cycles were documented. The analysis shows that the flashing green increases the number of early stops, as drivers tend to underestimate the duration of the time to the end of amber. Discrete choice models of the stopping behaviour are estimated for inclusion in suitable microsimulation models of traffic flow. The model results show that speed and distance to stop line, and their interaction (potential time to the stop line with unchanged speed) explain the stopping process.     

Changes in stress and subjective workload over time following a workload transition

Workload transitions present individuals with sudden changes in workload. These transitions may affect stress and coping behaviour. Two experiments were performed using a digit detection task that shifted between low and high workload levels to examine transition effects on performance, stress, and effort. The first experiment used a large magnitude transition and resulted in decreased estimates of task engagement and effort. Over time, the levels of subjective stress observed in the transitioned groups approached those of the non-transitioned control groups. The second experiment used a transition more moderate in magnitude. The results were similar to those from the first experiment except that the transition resulted in higher, sustained task engagement and effort. These findings indicate that over time, the perceived stress of transitioned individuals will approach those of non-transitioned individuals; however, the magnitude of the transition may influence individuals to either increase or decrease task-oriented, effortful coping.

Relevance to human factors/ergonomics theory

Previous research on the effect of workload transitions on experienced stress has produced conflicting results. Drawing upon transactional stress theory and motivational intensity theory, two experiments were conducted which resolve some of those conflicting findings. This research adds to our understanding of how workload transitions may affect individuals' experienced stress.     

挠性航天器姿态机动控制的主动振动抑制

针对喷嘴作为执行机构的挠性航天器大角度姿态机动时帆板的振动抑制问题,提出了伪速率(PSR)调制式喷气控制和基于压电陶瓷(PZT)材料的主动振动控制技术相结合的复合控制方法。首先,基于Lyapunov方法设计PD反馈控制器保证姿态的渐近稳定和模态振动的衰减性;为了减少喷嘴的非线性开关控制激起的挠性结构振动,采用PSR的准线性调制技术使喷嘴产生所需要的控制力矩的脉冲序列,从而在完成大角度姿态机动的同时抑制振动幅值较大的挠性模态的振动;通过设计正位置反馈(PPF)补偿器以增加结构的阻尼来进一步抑制挠性结构残余振动。最后,将该方法应用于航天器大角度rest-to-rest(静止到静止)姿态机动的仿真研究,结果表明:该方法不仅能够使航天器完成对姿态的机动,而且能够抑制帆板的挠性振动。     

Impact of perceptual treatments on lateral control during driving on crest vertical curves: a driving simulator study

Approximately 48% of all fatal collisions in Europe are classified as single-vehicle run-off-road or head-on collisions. These crashes relate to trajectory control (road departure) and represent a safety challenge. In France, single-vehicle run-off-road crashes represent 21% of all crashes and head-on collisions represent 11%. This study evaluated the effectiveness of four perceptual treatments (i.e., a painted center line, post-delineators, rumble strips on both sides of the center line and sealed shoulders) in supporting the driver to maintain lateral control; that is, to support the driver to keep in the center of his/her lane. Forty-three participants drove a fixed-base driving simulator, on a simulated straight 3 km rural road with two crest vertical curves (CVC). Four sections were chosen for analysis: a reference section (i.e., the first CVC), a test section (i.e., the second CVC), a pre-test section (i.e., immediately before the second CVC) and a post-test section (i.e., immediately after the second CVC). The results showed that drivers drive more at the center of their lane with the rumble strips on both sides of the center line and with the sealed shoulders than with the actual marking (here center line) or other treatments.