P017 Am I sleepy? – Subjective Sleepiness and Drowsy Driving: A systematic review and meta-analysis

Introduction Driving impairment due to sleep loss is a major contributor to motor vehicle crashes resulting in severe injury or fatalities. Ideally, drivers should be aware of their sleepiness and cease driving to reduce risk of a crash. However, there is little consensus on how accurately drivers can identify sleepiness, and how this relates to subsequent driving impairment. To examine whether drivers are aware of their sleepiness, we systematically reviewed the literature. Methods The research question for this review was “are drivers aware of sleepiness while driving, and to what extent does subjective sleepiness accurately reflect driving impairment?”. Our search strategy led to thirty-four simulated/naturalistic driving studies for review. We then extracted the relevant data. Correlational data were examined using meta-analysis, while predictive data were assessed via narrative review. Results Results showed that drivers were aware of sleepiness, and this was associated with both driving impairment and physiological drowsiness. Overall, subjective sleepiness was more strongly correlated (a) with ocular and EEG-based outcomes (rweighted = .70 and .73, respectively, p<.001), rather than lane position and speed outcomes (rweighted = .46 and .49, respectively, p<.001); (b) under simulated driving conditions compared to naturalistic drives; and (c) when the Karolinska Sleepiness Scale was used to measure subjective sleepiness. Lastly, high levels of sleepiness significantly predicted crash events and lane deviations. Discussion This review presents evidence that drivers are aware of sleepiness when driving, and suggests that interventions such as stopping driving when feeling ‘sleepy’ may significantly reduce crash risk.

Examining Driver Compliance with a Move-Over/Slow Down Law in Consideration of Vehicle Type and Messages Displayed on Upstream Dynamic Message Signs

Move-over laws are intended to enhance the safety of road agency and law enforcement personnel who are working on or near the roadway. This study examined driver behavior through a series of field studies where these types of vehicles were located on the outside shoulder of a freeway with their lights activated. The study also evaluated the use of upstream dynamic message signs (DMS) to discern whether targeted safety messages had any impact on behavior under this scenario. Upstream and downstream speed and lane position data were collected from vehicles originally traveling in the rightmost lane upstream of the DMS and emergency/service vehicle at two locations in Michigan. Logistic regression models were estimated to assess driver compliance with the law while considering important contextual factors, such as the type of vehicle on the shoulder and the message displayed on the DMS. The results indicated that drivers were more likely to move over or reduce their speeds when a police car was located on the shoulder as compared to a transportation agency pickup truck. In general, the type of message displayed had minimal impact on driver behavior. The one exception showed that drivers were likely to drive at or below the speed limit when targeted move-over messages were shown as compared to standard travel time messages. For all message types, both speed and lane compliance improved if the roadside vehicle was a police car.

Steering is initiated based on error accumulation

Vehicle control by humans is possible because the central nervous system is capable of using visual information to produce complex sensorimotor actions. Drivers must monitor errors and initiate steering corrections of appropriate magnitude and timing to maintain a safe lane position. The perceptual mechanisms determining how a driver processes visual information and initiates steering corrections remain unclear. Previous research suggests two potential alternative mechanisms for responding to errors: (i) perceptual evidence (error) satisficing fixed constant thresholds (Threshold), or (ii) the integration of perceptual evidence over time (Accumulator). To distinguish between these mechanisms an experiment was conducted using a computer-generated steering correction paradigm. Drivers (N=20) steered towards an intermittently appearing ‘road-line’ that varied in position and orientation with respect to the driver’s position and trajectory. One key prediction from a Threshold framework is a fixed absolute error response across conditions regardless of the rate of error development, whereas the Accumulator framework predicts that drivers would respond to larger absolute errors when the error signal develops at a faster rate. Results were consistent with an Accumulator framework, thus we propose that models of steering should integrate perceived control error over time in order to accurately capture human perceptual performance.

The effect of cellphone position on driving and gaze behaviour

Legislation frequently restricts the use of cellphones while driving. Despite this, many people continue to interact with cellphones covertly while driving, typically by concealing their device in their lap. This strategy leads to frequent diversion of the drivers’ gaze from the road ahead, potentially reducing their driving performance. To evaluate the influence of cellphone use on driving, 30 participants took part in three randomly ordered 7-min virtual reality driving simulations. In each condition, drivers were presented with either (a) no cellphone, (b) a cellphone fixed to the windscreen, or (c) a cellphone positioned at lap level. Their task was to maintain road position and observe speed limits while answering maths problems (delivered intermittently via ‘text message’) and searching for external target objects. Outcome measures included speed, lane position standard deviation (LPSD), and fixation behaviour, which were compared between trials. In trials where a cellphone was present, participants shifted fixation more frequently, drove approximately 6 km/h faster, exhibited a lower LPSD and spent more time in the correct lane on the road (compared to the no-cellphone condition; all p < 0.001). Cellphone position influenced eye gaze behaviour, with drivers looking at the cellphone less frequently, and the speedometer more frequently. when the cellphone was in their lap compared to when the cellphone was positioned on the windscreen. Our results are consistent with participants driving more cautiously—checking speed and lane position more frequently—when they have a cellphone in the lap. Real-world driving data would be useful to determine whether this change in driving behaviour we observed is sufficient to offset the increased risk introduced by spending less time looking at the road ahead.

Effectiveness of Warning Piles on Driving Behavior on the Curve of Low-Grade Highway

To develop a scientific and practicable guideline for implementing warning piles on Chinese low-grade highways, it is necessary to study the effect of warning piles on driving performance in different road alignments and environments. Based on a driving simulator, this paper evaluates the effect of unilateral and bilateral warning piles on vehicle speed and lateral position on a two-lane rural highway curve with different road geometries. The results show a significant effect of bilateral warning piles on speed control, which becomes more obvious as the radius of the curve decreases and the superelevation increases. In sharp curves, vehicle speed increases rapidly in the second half of the curve, and bilateral warning piles could significantly control speed increase to prevent danger. Meanwhile, the effect of bilateral warning piles on keeping vehicles in a safer lane position is also statistically significant in the second half of the curve. With a decreasing radius and an increasing superelevation, the value of the maximum lateral position will increase. Bilateral warning piles could reduce the lateral position to keep the vehicle on a stable track. Moreover, bilateral warning piles could also perform better at night. This paper studies both unilateral and bilateral warning piles’ effects on driving behavior in different road geometries, thus providing a theoretical basis for the engineering application of warning piles.

Evaluating and Enhancing Driving Skills for Individuals With Intellectual Disabilities Through Simulator Training

Research consistently demonstrates that attainment of a driver’s license and access to a vehicle directly and favorably influence employment outcomes, enhance one’s ability to capitalize on quality jobs, and expand one’s access to community and independent opportunities. This study used a driving simulator to provide driving lessons to 12 young adults with intellectual disabilities (IDs). The purpose was to use a safe learning environment to screen candidates for those who showed the potential to obtain a driver’s license. Instruction was provided using a set of interactive exercises focusing on controlling the vehicle via lane keeping, speed maintenance, and obstacle avoidance tasks. Results revealed that simulator training provided a safe learning environment to identify individuals demonstrating the potential to safely operate a motor vehicle. Participants demonstrated moderate to large gains in maintaining lane position, speed, braking response, and target detection. Implications and suggestions for future research are provided.

How Signs, Markings, and Hazards Impact Motorist Assessment of Cyclist Lane Placement

Human factors research has led to safer interactions between motorists through redesigned signage, roadway designs, and training. Similar efforts are needed to understand and improve interactions between cyclists and motorists. One challenge to safe motorist-cyclist interactions are expectations about where cyclists should be on the road. In this study, we utilize more directive signage and additional lane markings to clarify where cyclists should ride in the travel lane. The impact of these signifiers was examined by having motorists indicate where cyclists should ride in the lane, how difficult it was to determine the correct lane position, and how safe they would feel if they were in that lane position. Results indicate that more directive signage – “bicycles take the lane”-and painted hazard signifiers can change motorists’ expectations, so they are more aligned with safer cyclist positioning in the lane.

Evaluating Older Drivers in Their Everyday Driving Environments

Developing tools that accurately detect at-risk driving behaviors is a public-health priority. There is a need for a measure that accurately assesses older drivers’ level of competence on familiar roadways. The objective of this presentation is to describe the development of the procedures and scoring of a new approach, the Electronic Driving Observation Schedule (eDOS), to observe everyday driving in the community. The eDOS was used to record and compare the driving environment and performance of older drivers and low-risk younger drivers during their everyday driving. Older (n=160, &gt;74y) and younger (n=60, 35-64y) drivers completed a 20-30-minute drive from their home to destinations of their choice. Older drivers drove on simpler routes with fewer intersections and lane changes. Both groups made few driving errors, which were mostly low-risk. Younger drivers tended to demonstrate poor driving habits (not signaling, speeding, poor lane position) and compliance with road rules. Part of a symposium sponsored by Transportation and Aging Interest Group.

Tactile Vigilance Is Stressful and Demanding

Objective The primary aims of the study were to replicate the vigilance decrement in the tactile modality, examine whether a decrease in sensitivity is associated with the decrement, and determine whether tactile vigilance is stressful and demanding. Background When people monitor occasional and unpredictable signals for sustained durations, they experience a decline in performance known as the vigilance decrement, which has important practical consequences. Prior studies of the vigilance decrement focused primarily on visual vigilance and, to a lesser degree, on auditory vigilance. There are relatively few studies of tactile vigilance. Method Participants monitored vibrotactile stimuli that were created from a tactor, for 40 min. Results Sensitivity declined, self-report ratings of distress increased, and ratings of task engagement decreased, during the vigil, and perceived workload was moderately high. Conclusion Monitoring tactile signals is demanding and stressful and results in a decrement in signal detection. Application Monitoring tactile signals may result in a decrement in tasks requiring discrimination, such as monitoring lane position with the use of rumble strips; these require discrimination between current road vibration and increased vibration when the car drifts out of its lane and crosses over the strip.