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Microsleep Episodes, Attention Lapses and Circadian Variation in Psychomotor Performance in a Driving Simulation Paradigm
Get PDFNumerous studies document circadian changes in sleepiness, with biphasic peaks in the early morning and late afternoon. Driving performance has also been demonstrated to be subject to time-of-day variation. This study investigated circadian variation in driving performance, attention lapses (AL) and/or frequency of microsleep (MS) episodes across the day. Sixteen healthy adults with valid driver’s licenses participated in the study. Using the York Driving Simulator, subjects performed four intentionally soporific 30-minute driving simulations at two-hour intervals (i.e., at 10:00, 12:00, 14:00, and 16:00). During each session, individuals had EEG monitoring for MS episodes (defined as 15 to 30 seconds of any sleep stage by polysomnographic criteria) and AL episodes (defined as intrusion of alpha- or theta-EEG activity lasting 4-14 seconds). Measured variables included: lane accuracy, average speed, speed deviation, mean reaction time (RT) to “virtual” wind gusts and off-road events. Mean values of each variable at every time were analyzed using a general linear model and paired sample t-tests. RT displayed significant within-group variation, with paired samples tests at df=15 showing RT at 10:00 significantly faster than at other times of the day, but no significant within-group variation between other times of the day. All other variables and EEG-defined AL episodes failed to exhibit any statistically significant variation across the day. However, MS episodes were found to occur more often at 16:00 in comparison to all other times. As RT was optimal before noon, it appears that psychomotor performance and therefore driving ability is subject to circadian variation. Coincident with the demonstrated circadian pattern of diminished alertness, this may partially explain the high incidence of motor vehicle accidents during the mid- to late-afternoon. By better understanding circadian fluctuations in driver sleepiness and psychomotor performance, human performance researchers may be in a position to better educate the public about cautionary measures to prevent accidents
The Effects of Fatigue on Driver Performance for Single and Team Long-Haul Truck Drivers
Get PDFDriver fatigue is an important safety issue for long-haul truck drivers. To provide an efficient means of obtaining sleep, long-haul truck drivers often use tractors equipped with sleeper berth units. Depending on the type of cargo and distances traveled, long-haul truck drivers either drive in teams or alone as single drivers. Team drivers, therefore, typically sleep in a moving truck whereas single drivers sleep in a stationary truck. It has been hypothesized that sleeping in a moving truck could adversely affect the sleep quality and, therefore, the alertness level of team drivers. A naturalistic data collection system was developed and installed in two Class 8 heavy trucks. This trigger-based system consisted of vehicle sensors and cameras that allowed the experimenters to obtain the driving performance and driver alertness data for analysis of fatigue. Fatigue was measured using both objective and subjective measures that were recorded before and after sleep and while driving. Fatigue and driving performance were compared for single versus team drivers to determine which driver type acquired the greatest sleep deficit during a trip. Results suggest that single drivers were more frequently involved in critical incidents while exhibiting extreme drowsiness than were team drivers by a factor of 4 to 1. These results will be discussed in relation to the general safety of single versus team trucking operations
Driver Preference of Collision Warning Strategy and Modality
Get PDFThe success of collision warning systems depends on how well the algorithm and driver interface are tailored to driver capabilities and preferences. An effective collision warning system must promote a timely and appropriate driver response while minimizing annoyance associated with nuisance warnings. A within-subject experimental design examined warning strategy and modality by contrasting graded and imminent warning strategies with auditory and haptic warning modalities. Presented on a high, head-down display placed directly in front of the driver, visual warnings were displayed in the form of graded bars representing severity, or by an imminent collision icon. Visual warnings were paired with either an auditory warning or a haptic warning in the form of a vibrating seat. Results suggest that haptic warnings may be preferred over auditory warnings, with graded haptic warnings being preferred more than imminent haptic warnings. These results support previous findings of greater acceptance of graded compared to imminent warnings, and no decrement in performance or acceptance of a haptic versus an auditory warning
Driver Psychological Types and Car Following: Is there a Correlation? Results of a Pilot Study
Get PDFMany studies have attempted to measure driver behaviour or to classify drivers’ attributes according to questionnaires based on psychological indicators. Although such studies have met with success, for example, correlating behavioural types with accident risk, few attempts have been made to correlate these attributes with direct, dynamically measurable quantities such as desired following distance or its responsiveness to speed changes. In this paper we will examine whether such a correlation is possible by examining results from a pilot study using an instrumented vehicle and a group of eleven subjects. In particular we will focus on how following distances are correlated to the Sensation Seeking and Internality-Externality Scale
Simulator Training Improves Driver Efficiency: Transfer from the Simulator to the Real World
Get PDFHere we report the results of a fuel management simulation study to quantify the improvement in fuel efficiency for CDL truck drivers. Forty drivers were selected from a local commercial trucking company that maintained precise records on drivers’ history, fuel efficiency, type of vehicles driven, and trucking routes. These drivers participated in a two-hour training program that focused on ways to optimize shifting to maximize fuel efficiency (e.g., progressive shifting, double clutching, timing, and appropriate gear selection). Transfer of training was assessed over a six-month interval using measures of fuel consumption obtained by drivers in their own vehicles driving their normal route. Training increased fuel efficiency by an average of 2.8% over the six-month interval. Analyses indicated that the benefits of training persisted throughout the posttraining interval. These training benefits were obtained even for the subset of drivers who changed vehicles after training, indicating that drivers learned a general skill that transferred from one vehicle to another. Additional analyses focused on which drivers benefited the most from training. We sorted the drivers into one of four groups, based on pre-training fuel efficiency. Our analysis indicated that those drivers with the lowest pre-training fuel efficiency benefited most from training (with over 7% improvement in fuel efficiency), while those with the highest pre-training fuel efficiency did not benefit significantly from training. Together, our data validated the transfer of simulator training to realworld driving, as drivers incorporated the methods of optimal shifting into their driving practices. Moreover, the benefits of training appear to be durable and tend to benefit most those drivers whose performance was initially below the median on fuel efficienc
An Abstract Virtual Environment Tool to Assess Decision-Making Impaired Drivers
Get PDFWe describe design and pilot testing of software for evaluating decision-making abilities in drivers with neurological impairments. Instead of striving for visual realism, the virtual environment software is based on a more abstract representation that provides necessary visual cues in a singlescreen setting. Pilot tests were conducted on 16 subjects with neurological impairments (14 with focal brain lesions, two with Alzheimer’s disease), and 16 neurologically normal subjects. Preliminary results are promising, suggesting that the PC-based virtual environment tool can distinguish decision-making impaired people where traditional neurological test batteries canno
Effects of Cognitive Tasks on Drivers' Eye Behavior and Performance
No full textSafe driving involves obtaining and using required visual information. Recent studies have shown that this information acquisition is compromised as a driver performs other mental tasks. We conducted an experiment, inspired by Recarte and Nunes (2000), to investigate the effect of cognitive tasks on drivers’ eye behavior and performance in a single monitor, PC-based driving simulator. The eye behavior (i.e., gaze direction and duration) and driving performance (i.e., lane keeping and speed control) of twelve college students were recorded as they drove in three environments (i.e., highway, rural, urban) under three secondary task conditions (none, verbal task, spatial-imagery task). The results confirmed Recarte and Nunes (2000) observation that such tasks greatly reduce the time and frequency of such safety-related behaviors as checking the speedometer and rear view mirrors, with the spatial-imagery task having the largest effect. Pupil diameter increases significantly when performing secondary tasks, confirming the usefulness of that measure as an indicator of processing load. In contrast, these secondary tasks have no effect on lane-keeping accuracy, though they do increase variation in speed. From the perspective of multiple resource theory (Wickens, 2002; Wickens & Hollands, 2000), this suggests that lane keeping, speed control and other safety-monitoring activities (i.e., checking mirrors and speedometer) all require attentional resources, and that when resources must be given to some new task, there is a prioritization of the remaining tasks. Lane-keeping, the failure of which would produce the most apparent driving failures, is given the highest priority, with other safetymonitoring activities given lower priority. The method employed here can be used to examine the effect of driver activities and devices on their monitoring of safety-related information
Multiple Resource Modeling of Task Interference in Vehicle Control, Hazard Awareness and In-vehicle Task Performance
Get PDFWe describe a computational model of multiple task performance used to predict task interference and subsequent decrements in performance, based on the resource demands of a particular task (i.e., the difficulty) as well as the competition between tasks over limited and overlapping resources. We describe the model components, the computational aspects, and further validate it with data from a simulated driving study
Traffic Entry Judgments by Aging Drivers
Get PDFWe hypothesized that older, neurologically normal drivers would compensate appropriately for their slower abilities by choosing larger gaps when entering traffic. To test this we used an instrumented vehicle and radar gun to study 18 legally licensed, neurologically normal drivers ranging from 22 to 72 years old. Drivers were asked to press a button to mark the last possible moment they would cross the road in front of an oncoming vehicle. We measured speed and distance of the oncoming vehicles and calculated time-to-contact (TTC). The older drivers made more conservative gap acceptance decisions based on higher TTC than younger drivers. This pilot study identified trends in effects of age upon traffic entry judgments, suggesting that neurologically normal older drivers are more conservative when deciding to enter traffic than younger drivers
Societal Violence, Driver Age, and Attained Education: Independent Contributions to Road Accidents?
Get PDFTwenty years ago, an analysis (Sivak, 1983) showed that homicide rates and proportion of young drivers were significant and independent predictors of states’ fatal accident rates. In the present study, we revisited these relationships by examining the data for year 2000, and included attained education as an additional independent variable. The goal was to provide evidence concerning the degree of independent contribution of violence, driver age, and education to current accident patterns. A regression analysis was performed using the 2000 fatal accident data for the 50 individual states (excluding D.C.). The dependent variable was the fatal accident rate per licensed driver. There were three independent variables: the homicide rate per person, the proportion of licensed drivers under 20 years of age, and the proportion of persons that attained at least a college degree among the population aged 25 years and older. Consistent with Sivak (1983), both the homicide rate and the proportion of young drivers were significant predictors of states’ fatal accident rate, but so also was the proportion of college graduates. Specifically, a higher traffic fatality rate was associated with a higher homicide rate, a higher proportion of young drivers, and a lower proportion of college graduates. The respective simple correlation were 0.35, 0.50, and -0.66. A multiple regression showed that each of these three independent variables has a significant and independent relationship with the dependent variable. The three predictors accounted for a total of 63% of the variance in the traffic fatality rate. The present analysis indicates strong independent relationships between states’ homicide rate, proportion of young drivers, and attained education on one hand and states’ fatal accident rate on the other hand. However, because this was an observational study, causal relationships cannot be directly inferred. For example, from this multiple regression it is not possible to exclude the possibility that the apparent effects of the three independent variables stand for the effects of other, not explicitly identified variables. Nevertheless, the present results are consistent with the possibility of independent contributions to traffic accident causation of the level of societal violence, inexperience/risk taking of young drivers, and level of education. The presentation discusses the potential implication of these findings, along with methodological issues related to these kinds of analyses