Methods for evaluating driver-road interactions, a pilot study

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of City & Regional Planning, 1964.Includes bibliographical references (leaves 191-192).by Mayer David Spivack.M.C.P

Driver fatigue and performance decrements over time-on-task: Effects and mitigation

Road crashes are a leading cause of death by injury globally (WHO, 2018), with fatigue estimated to contribute to 17% of fatal crashes (Tefft, 2012; TfNSW, 2017). A century of research has advanced our knowledge regarding the causes and effects of fatigue, but much remains unknown. In particular, while there is evidence that both heightened sleep-need and characteristics of the driving task can give rise to fatigue, the relative and combined effects of these factors are not sufficiently understood. Also, while several potential task-based fatigue interventions have been suggested, the effectiveness of these potential interventions is not well established. The present research is comprised of three empirical, driving simulator-based studies that aim to enhance our current understanding of the causes and possible mitigators of driver fatigue. The first study aimed to determine the contributions of time-on-task and sleep restriction, individually and combined, on the development of driver fatigue and performance impairment, and to investigate the potentially protective effects of a simple task modification. Sixty participants drove a simulated, monotonous route for 2 hours, under conditions of either prior sleep restriction or no sleep restriction, and with either normal speed limit signs or signs that required calculation of a mathematical problem, which has previously been shown to protect performance (Dunn & Williamson, 2012). Results clearly demonstrate that both sleep restriction and time-on-task contribute independently to driver fatigue, but there was some indication that sleep-restricted drivers could initially protect their performance, perhaps through the exertion of greater effort. The speed sign manipulation failed to show any protective effects. The second study was designed to further examine the effect of task-factors on driver state and performance over time-on-task. Exposure to a secondary cognitive task has been found to improve driving performance during the period of exposure, but the effects of this intervention over the duration of a drive has received limited attention. This study specifically investigated whether repeated exposures to a secondary task can overcome the degradation of performance and subjective state that occurs over time-on-task, whether any such benefits are dependent on the cognitive workload imposed by the task, and whether these beneficial effects might be attributable to increased effort. This study (N = 17, fully within participants design) employed a secondary cognitive task commonly found to elicit temporally limited beneficial effects in driving performance (n-back task), presenting it three times during an otherwise monotonous 90-minute simulated drive. Each participant performed three drives, one in each of three conditions, with order of condition counterbalanced between participants. The three conditions involved either three periods of 2-back (higher cognitive workload), three periods of 0-back (lower cognitive workload), or no n-back task (control). Results demonstrated that the 2-back condition marginally improved driving performance during exposure but neither condition reduced the degradation of performance or subjective state over time-on-task. The third study built upon study two by exploring whether increasing the frequency of secondary-task exposures would result in reduced performance decrements over time and also by comparing the effect of secondary-task exposure to the effect of taking breaks from driving, which is currently the typical advice provided to drivers to counteract fatigue and performance decrements. This study involved ninety-two participants driving a simulated, monotonous route for 90 minutes in one of six conditions: Driving only (control); infrequent 2-back exposure (three exposures, as per study 2); frequent 2-back exposure (five exposures); continuous 2-back exposure throughout the drive; infrequent breaks (three breaks); or frequent breaks (five breaks). Results indicate that infrequent exposure to a secondary task sustained driving performance over 90-minutes of time-on-task, which is inconsistent with the findings of study 2. Contrary to expectations, frequent secondary-task exposure was less beneficial than infrequent exposure, providing no benefit over the control condition. Continuous secondary-task exposure was detrimental to performance over time-on-task. The provision of breaks from driving also sustained driving performance over time-on-task, with more frequent breaks providing marginally greater benefit than less frequent breaks. Providing participants with breaks from driving was also beneficial for subjective states, measured as sleepiness, fatigue and effort. Results also confirmed that performance improvements in the secondary-task conditions were not solely a result of increased effort. These studies demonstrate that continuous time-on-task driving in highway-like conditions has a robust fatiguing effect. This effect is independent of, but exacerbated by, receiving insufficient sleep, highlighting the importance of taking continuous operating time into consideration, even in the context of seemingly simple tasks and when drivers are well-slept. Additionally, these studies demonstrate that repeated exposure to a secondary task might be an effective intervention for sustaining performance during monotonous drives of at least 90-minutes duration, but the nature and frequency of such interventions appear to be a key factor in their effectiveness. Results also suggest that performance might be best sustained by taking very frequent breaks, and although this might be impractical in the context of driving, this finding might be applied to a broad range of tasks that require sustained attention, including operations in security and quality control