Catherine Berthelon

Mental workload and driving

The aim of this review is to identify the most representative measures of subjective and objective mental workload in driving, and to understand how the subjective and objective levels of mental workload influence the performance as a function of situation complexity and driving experience, i.e., to verify whether the increase of situation complexity and the lack of experience increase the subjective and physiological levels of mental workload and lead to driving performance impairments. This review will be useful to both researchers designing an experimental study of mental workload and to designers of drivers’ training content. In the first part, we will broach the theoretical approach with two factors of mental workload and performance, i.e., situation complexity and driving experience. Indeed, a low complex situation (e.g., highways), or conversely a high complex situation (e.g., town) can provoke an overload. Additionally, performing the driving tasks implies producing a high effort for novice drivers who have not totally automated the driving activity. In the second part, we will focus on subjective measures of mental workload. A comparison of questionnaires usually used in driving will allow identifying the most appropriate ones as a function of different criteria. Moreover, we will review the empirical studies to verify if the subjective level of mental workload is high in simple and very complex situations, especially for novice drivers compared to the experienced ones. In the third part, we will focus on physiological measures. A comparison of physiological indicators will be realized in order to identify the most correlated to mental workload. An empirical review will also take the effect of situation complexity and experience on these physiological indicators into consideration. Finally, a more nuanced comparison between subjective and physiological measures will be established from the impact on situation complexity and experience.

Curvilinear approach to an intersection and visual detection of a collision

Visual motion perception plays a fundamental role in vehicle control. Recent studies have shown that the pattern of optical flow resulting from the observers self-motion through a stable environment is used by the observer to accurately control his or her movements. However, little is known about the perception of another vehicle during self-motion-for instance, when a car driver approaches an intersection with traffic. In a series of experiments using visual simulations of car driving, we show that observers are able to detect the presence of a moving object during self-motion. However, the perception of the other cars trajectory appears to be strongly dependent on environmental factors, such as the presence of a road sign near the intersection or the shape of the road. These results suggest that local and global visual factors determine the perception of a cars trajectory during self-motion.

The evaluation of traditional and early driver training with simulated accident scenarios

Objective: We assessed the driving skills of novice traditionally trained, novice early-trained, and experienced drivers to evaluate whether supervised early training could improve young drivers’ skills. Background: The overall representation of young male drivers in car crashes is a recurrent problem in developed countries. To prevent this overrepresentation, France institutes an early driver training program from the age of 16 with the supervision of an adult. However, evidence of the positive effects of this system is still lacking. Method: Three groups of drivers (12 participants each) were confronted with five prototypical accident scenarios introduced in a simulated urban circuit. Drivers’ response time, speed, and vehicle position in the lane were analyzed. Results: No difference was detected across groups regarding obstacle detection, as revealed by the analysis of response times. But in some unexpected scenarios, position control by traditionally trained drivers was more conservative than for more experienced drivers, and early-trained drivers were far more likely to respond with efficient evasive action. Conclusion: The exposure gained by an early training program could thus increase the development of visuomotor coordination and involve better skills in challenging situations. Application: The supplementary driving experience gained with the supervision of an adult during early training could promote the skills necessary to deal with risky situations. Driving simulators could be used to confront young drivers with a broad range of hazardous scenarios not commonly encountered in natural driving.

Intersection crossing considered as intercepting a moving traffic gap: Effects of task and environmental constraints

Safely crossing an intersection requires that drivers actively control their approach to the intersection with respect to characteristics of the flow of incoming traffic. To further our understanding of the perceptual-motor processes involved in this demanding manoeuvre, we designed a driving simulator experiment in which 13 participants actively negotiated intersections by passing through a gap in the train of incoming traffic. Task constraints were manipulated by varying the size of the traffic gap and the initial conditions with respect to the time of arrival of the traffic gap at the intersection. Environment constraints were manipulated by varying the intersection geometry through changes in the angle formed by the crossroads. The results revealed that the task constraints systematically gave rise to continuous and gradual adjustments in approach velocity, initiated well before arriving at the intersection. These functionally appropriate adjustments allowed the drivers to safely cross the intersection, generally just slightly ahead of the center of the traffic gap. Notwithstanding the fact that the geometry of the intersection did not affect the spatiotemporal constraints of the crossing task, approach behavior varied systematically over geometries, suggesting that drivers rely on the traffic gaps bearing angle. Overall, the pattern of results is indicative of a continuous coupling between perception and action, analogous to that observed in locomotor interception tasks.

Divided attention in young drivers under the influence of alcohol

INTRODUCTION The present research evaluates driving impairment linked to divided attention task and alcohol and determines whether it is higher for novice drivers than for experienced drivers. METHOD Novice and experienced drivers participated in three experimental sessions in which blood alcohol concentrations (BACs) were 0.0 g/L, 0.2 g/L, and 0.5 g/L. They performed a divided attention task with a main task of car-following task and an additional task of number parity identification. Driving performance, response time and accuracy on the additional task were measured. RESULTS ANOVA showed a driving impairment and a decrease in additional task performance from a BAC of 0.5 g/L, particularly for novice drivers. Indeed, the latter adopt more risky behavior such as tailgating. In the divided attention task, driving impairment was found for all drivers and impairment on information processing accuracy was highlighted, notably in peripheral vision. PRACTICAL APPLICATIONS The divided attention task used here provides a relevant method for identifying the effects of alcohol on cognitive functions and could be used in psychopharmacological research.

Intercepting a moving traffic gap while avoiding collision with lead and trail vehicles: Gap-related and boundary-related influences on drivers' speed regulations during approach to an intersection

Using a fixed-base driving simulator, 15 participants actively drove their vehicle across a rural road toward an intersection. Their task was to safely cross the intersection, passing through a gap in the train of incoming traffic. Spatiotemporal task constraints were manipulated by varying the initial conditions (offsets) with respect to the time of arrival of the traffic gap at the intersection. Orthogonally manipulating the motion characteristics of the lead and trail vehicles forming the traffic gap allowed evaluating the influences of the global (gap-related) and local (lead/trail-vehicle-related) aspects of the inter-vehicular interval. The results revealed that the different initial offsets gave rise to functional, continuous and gradual adjustments in approach speed, initiated early on during approach to the intersection. Drivers systematically accelerated during the final stages of approach, on average crossing the gap slightly ahead of the center of the traffic gap. A special-purpose ANOVA demonstrated an influence of (global) gap characteristics such as gap size and speed. Further analyses demonstrated that the motion characteristics of the lead vehicle exerted a stronger influence on approach behavior than the motion characteristics of the trail vehicle. The results are interpreted as signing the online regulation of approach speed, concurrently based on intercepting the (center of the) traffic gap and avoiding collision with the lead and trail vehicles.

Overload depending on driving experience and situation complexity: Which strategies faced with a pedestrian crossing?

The purpose of this study was to identify the influence of situation complexity and driving experience on subjective workload and driving performance, and the less costly and the most effective strategies faced with a hazard pedestrian crossing. Four groups of young drivers (15 traditionally trained novices, 12 early-trained novices, 15 with three years of experience and 15 with a minimum of five years of experience) were randomly assigned to three situations (simple, moderately complex and very complex) including unexpected pedestrian crossings, in a driving simulator. The subjective workload was collected by the NASA-TLX questionnaire after each situation. The main results confirmed that the situation complexity and the lack of experience increased the subjective workload. Moreover, the subjective workload, the avoidance strategies and the reaction times influenced the number of collisions depending on situation complexity and driving experience. These results must be taken into account to target the prevention actions.

Measuring mental workload with the NASA-TLX needs to examine each dimension rather than relying on the global score: an example with driving

Abstract The distinction between several components of mental workload is often made in the ergonomics literature. However, measurements used are often established from a global score, notably with several questionnaires that originally reflect several dimensions. The present study tested the effect of driving situation complexity, experience and subjective levels of tension and alertness on each dimension of the NASA-TLX questionnaire of workload, in order to highlight the potential influence of intrinsic, extraneous and germane load factors. The results showed that, in complex situation, mental, temporal and physical demand (load dimensions) increased, and that novice drivers presented high physical demand when subjective tension was low on performance. Moreover, increase of mental and physical demand increased effort. It thus, appears essential to distinguish the different components of mental workload used in the NASA-TLX questionnaire. Practitioner Summary: Currently, global score of NASA-TLX questionnaire is used to measure mental workload. Here, we considered independently each dimension of NASA-TLX, and results showed that mental load factors (driving situation complexity, experience, subjective tension and alertness) had a different effect on dimensions, questioning global score use to evaluate workload.

Information–Movement Coupling in The Control of Driver Approach to an Intersection

ABSTRACT We characterized the control mechanisms underlying crossing an intersection with vehicular traffic. Specifically, we identified potential markers of the coupling between information and movement through a kinematic analysis of the approach. We exposed participants in a driving simulator experiment to several scenarios. We manipulated task constraints by varying the acceleration capabilities of the vehicle and the time available to make speed adjustments. The results highlighted gradual, systematic adjustments, which make it possible to cross the intersection in a zone that is close to the center of the intervehicular gap. The functional nature of these adjustments was highlighted by concomitant and opposite variation in the variability of current speed and current deviation. In all cases, an increase in the standard deviation of speed was accompanied by a reduction in the standard deviation of current deviation. Neither time to make adjustments nor acceleration capabilities modified the observed kinematic patterns, but they did modulate the adjustments that were produced. Overall, these results were consistent with a control mechanism based on the implementation of an information–movement cycle.

Is the Driving Behaviour of Young Novices and Young Experienced Drivers Under Alcohol Linked to Their Perceived Effort and Alertness

The aim is to evaluate effort and alertness perception and objective driving performance of young drivers depending on Blood Alcohol Concentration (BAC) and driving experience. Young novice and young experienced drivers participated in three simulated driving sessions (BACs of 0.0, 0.2 and 0.5 g/L). They had to drive during 45 min. on a simulated highway road. After each driving session, they responded to the Thayer scale and to an adaptation of the NASA-TLX. Results showed that young experienced drivers estimated to make less effort and had better driving performance than young novice drivers. Estimated alertness level was the lowest and speed variation was the highest with BAC 0.5 g/l. It also existed an interaction effect between perceived effort and alcohol and between alertness and alcohol on driving performance. In summary, alcohol degrades driving performance, and especially when the effort is high, alertness is low and drivers lack experience.