Obstacle avoidance under automated steering: Impact on driving and gaze behaviours

Within the context of more and more autonomous vehicles, an automatic lateral control device (AS: Automatic Steering) was used to steer the vehicle along the road without drivers’ intervention. The device was not able to detect and avoid obstacles. The experiment aimed to analyse unexpected obstacle avoidance manoeuvres when lateral control was delegated to automation. It was hypothesized that drivers skirting behaviours and eye movement patterns would be modified with automated steering compared with a control situation without automation. Eighteen participants took part in a driving simulator study. Steering behaviours and eye movements were analysed during obstacle avoidance episodes. Compared with driving without automation, skirting around obstacles was found to be less effective when drivers had to return from automatic steering to manual control. Eye movements were modified in the presence of automatic steering, revealing further ahead visual scanning of the driving environment. Resuming manual control is not only a problem of action performance but is also related to the reorganisation of drivers’ visual strategies linked to drivers’ disengagement from the steering task. Assistance designers should pay particular attention to potential changes in drivers’ activity when carrying out development work on highly automated vehicles.     

Eye-hand coordination asymmetries in manual aiming

The authors investigated whether movement-planning and feedback-processing abilities associated with the 2 hand-hemisphere systems mediate illusion-induced biases in manual aiming and saccadic eye movements. Although participants' (N = 23) eye movements were biased in the direction expected on the basis of a typical Müller-Lyer configuration, hand movements were unaffected. Most interesting, both left- and right-handers' eye fixation onset and time to hand peak velocity were earlier when they aimed with the left hand than they were when they aimed with the right hand, regardless of the availability of vision for online movement control. They thus adapted their eye-hand coordination pattern to accommodate functional asymmetries. The authors suggest that individuals apply different movement strategies according to the abilities of the hand and the hemisphere system used to produce the same outcome.     

The role of visual and nonvisual feedback in a vehicle steering task

This article investigates vehicle steering control, focusing on the task of lane changing and the role of different sources of sensory feedback. Participants carried out 2 experiments in a fully instrumented, motion-based simulator. Despite the high level of realism afforded by the simulator, participants were unable to complete a lane change in the absence of visual feedback. When asked to produce the steering movements required to change lanes and turn a corner, participants produced remarkably similar behavior in each case, revealing a misconception of how a lane-change maneuver is normally executed. Finally, participants were asked to change lanes in a fixed-based simulator, in the presence of intermittent visual information. Normal steering behavior could be restored using brief but suitably timed exposure to visual information. The data suggest that vehicle steering control can be characterized as a series of unidirectional, open-loop steering movements, each punctuated by a brief visual update.     

Preparing lane changes while driving in a fixed-base simulator: Effects of advance information about direction and amplitude on reaction time and steering kinematics

Reaction times (RTs) of aiming movements are typically shorter when responses are prepared by informative precues. Aside from RT facilitation, response preparation can also modify the velocity profile of the movement trajectory. In this study we assess the preparatory effects of advance information about direction and number of lanes in a lane change task. Consistent with the findings of previous studies with aiming movements, prior information reduced RT and affected the velocity profile of the steering angle. The velocity profile was mainly shortened around the first peak steering wheel angle, and this finding is in line with the movement integration hypothesis. The results suggest that the findings from basic research can be generalized to driving tasks.     

Eye-hand coordination: spatial localization after saccadic and pursuit eye movements

Subjects produced speeded and unspeeded hand movements to a target location after either saccadic or pursuit eye movements to the target. Hand movements began either aligned with the initial position of gaze or from some other location. Subjects generally underestimated the extent of the pursuit eye movements relative to estimates made after saccades. With speeded hand movements, however, the underestimation was reduced considerably if the hand movements began aligned with a location other than the initial position of gaze. The results reveal details of the mechanisms underlying eye-hand coordination and show that important differences exist in the information used for localization for slow and rapid limb movements.     

Microsaccades keep the eyes' balance during fixation

During fixation of a stationary target, small involuntary eye movements exhibit an erratic trajectory-a random walk. Two types of these fixational eye movements are drift and microsaccades (small-amplitude saccades). We investigated fixational eye movements and binocular coordination using a statistical analysis that had previously been applied to human posture control. This random-walk analysis uncovered two different time scales in fixational eye movements and identified specific functions for microsaccades. On a short time scale, microsaccades enhanced perception by increasing fixation errors. On a long time scale, microsaccades reduced fixation errors and binocular disparity (relative to pure drift movements). Thus, our findings clarify the role of oculomotor processes during fixation.     

Training older adults to search more effectively: scanning strategy and visual search in dynamic displays

The authors examined the ability of older adults to modify their search strategies to detect changes in dynamic displays. Older adults who made few eye movements during search (i.e., covert searchers) were faster and more accurate compared with individuals who made many eye movements (i.e., overt searchers). When overt searchers were instructed to adopt a covert search strategy, target detection performance increased to the level of natural covert searchers. Similarly, covert searchers instructed to search overtly exhibited a decrease in target detection performance. These data suggest that with instructions and minimal practice, older adults can ameliorate the cost of a poor search strategy.     

Effects of visual and cognitive load in real and simulated motorway driving

As part of the HASTE European Project, effects of visual and cognitive demand on driving performance and driver state were systematically investigated by means of artificial, or surrogate, In-vehicle Information Systems (S-IVIS). The present paper reports results from simulated and real motorway driving. Data were collected in a fixed base simulator, a moving base simulator and an instrumented vehicle driven in real traffic. The data collected included speed, lane keeping performance, steering wheel movements, eye movements, physiological signals and self-reported driving performance. The results show that the effects of visual and cognitive load affect driving performance in qualitatively different ways. Visual demand led to reduced speed and increased lane keeping variation. By contrast, cognitive load did not affect speed and resulted in reduced lane keeping variation. Moreover, the cognitive load resulted in increased gaze concentration towards the road centre. Both S-IVIS had an effect on physiological signals and the drivers’ assessment of their own driving performance. The study also investigated differences between the three experimental settings (static simulator, moving base simulator and field). The results are discussed with respect to the development of a generic safety test regime for In-vehicle Information Systems.     

Effect of time pressure on steering control of the drivers in a car-following situation

The current study focused on analyzing steering control of the drivers during a car-following situation under increasing time pressure conditions. A driving simulator experiment was conducted on ninety-two participants to assess steering performance measures. Five different steering control measures: Variability in Steering Angle (VSA), Steering Reversal Rate (SRR), Steering Speed (SS), Stability of Steering Control (SSC), and Maximum Steering Swerve (MSS) were examined under No Time Pressure (NTP), Low Time Pressure (LTP), and High Time Pressure (HTP) driving conditions. Repeated measures ANOVA (for continuous data) and Friedman’s test (count data) with post-hoc analysis and Generalized Estimating Equation (GEE) modeling technique were used to investigate the influence of time pressure and different predictor variables. The statistical analysis showed that time pressure driving conditions significantly affected steering control of the drivers. The pairwise comparison of time pressure conditions revealed that HTP significantly affected most of the steering control measures as compared to LTP. Further, a GEE model also exhibited similar results where steering control measures were substantially influenced by HTP as compared to LTP. Moreover, in addition to time pressure conditions, demographic characteristics showed significant influence on steering control measures. The GEE model results showed that female drivers performed 13% more steering corrections (5° SRR) which led to better SSC by 124.44% than male drivers. Additionally, it was discovered that young-aged and experienced drivers took extra steering efforts to control lateral position of the vehicle by increasing 53.50% SS and 1% SRR compared to middle-aged and inexperienced drivers. The findings from the current study revealed that drivers undergo fast and abrupt steering maneuvers under time pressure conditions. The research approach demonstrated in the current study can be beneficial to discriminate minimum requirement of steering efforts and set-up threshold values for various steering evasion techniques to control and maintain safe lateral position during car-following maneuvers.     

Saccadic output is influenced by limb kinetics during eye-hand coordination

In several recent studies, saccadic eye movements were found to be influenced by concurrent reaching movements. The authors investigated whether that influence originates in limb kinematic or kinetic signals. To dissociate those 2 possibilities, the authors required participants (N = 6) to generate pointing movements with a mass that either resisted or assisted limb motion. With practice, participants were able to generate pointing responses with very similar kinematics but whose kinetics varied in a systematic manner. The results showed that saccadic output was altered by the amount of force required to move the arm, consistent with an influence from limb kinetic signals. Because the interaction occurred before the pointing response began, the authors conclude that a predictive signal related to limb kinetics modulates saccadic output during tasks requiring eye-hand coordination.     

Alternating Adaptation of Eye and Hand Movements to Opposite Directed Double Steps

Eye and hand movements can adapt to a variety of sensorimotor discordances. Studies on adaptation of movement directions suggest that the oculomotor and the hand motor system access the same adaptive mechanism related to the polarity of a discordance, because concurrent adaptations to opposite directed discordances strongly interfere. The authors scrutinized whether participants adapt their hand and eye movements to opposite directions (clockwise/counterclockwise) when both motor systems are alternatingly exposed to opposite directed double steps, and whether such adaptation is influenced by the allocation of effector to adaptation direction. The results showed that hand and eye movements adapted to opposite directions, but adaptation was biased to the counterclockwise direction. Aftereffects emerged nearly unbiased and independently for both motor systems. The authors conclude that the oculomotor and the hand motor system use independent mechanisms when they adapt to opposite polarities, although they interact during adaptation or concurrent performance.     

Eye-Hand Coordination in Rhythmical Pointing

The authors investigated the relation between hand kinematics and eye movements in 2 variants of a rhythmical Fitts's task in which eye movements were necessary or not necessary. P. M. Fitts's (1954) law held in both conditions with similar slope and marginal differences in hand-kinematic patterns and movement continuity. Movement continuity and eye—hand synchronization were more directly related to movement time than to task index of difficulty. When movement time was decreased to fewer than 350 ms, eye—hand synchronization switched from continuous monitoring to intermittent control. The 1:1 frequency ratio with stable π/6 relative phase changed for 1:3 and 1:5 frequency ratios with less stable phase relations. The authors conclude that eye and hand movements in a rhythmical Fitts's task are dynamically synchronized to produce the best behavioral performance.     

Global effect of a nearby distractor on targeting eye and hand movements

Eye-hand coordination was investigated with the global effect paradigm. In this paradigm, saccades typically land in between the target and a nearby presented distractor, the configuration's center of gravity. This so-called global effect, or spatial averaging, is attributed to incomplete target selection. Four experiments demonstrated a similar effect for hand movements; thus, eye and hand are coupled during target selection. However, under some conditions the global effect was different for eye and hand, suggesting that their coupling is not achieved through a shared target representation. Instead, eye and hand seem to use 2 separate target representations that exchange information. The convergent amplitudes of eye and hand with simultaneous execution support this interpretation. Latencies showed a similar converging pattern.     

From vision to action: experiments and models of steering control during driving

Experienced drivers performed simple steering maneuvers in the absence of continuous visual input. Experiments conducted in a driving simulator assessed drivers' performance of lane corrections during brief visual occlusion and examined the visual cues that guide steering. The dependence of steering behavior on heading, speed, and lateral position at the start of the maneuver was measured. Drivers adjusted steering amplitude with heading and performed the maneuver more rapidly at higher speeds. These dependencies were unaffected by a 1.5-s visual occlusion at the start of the maneuver. Longer occlusions resulted in severe performance degradation. Two steering control models were developed to account for these findings. In the 1st, steering actions were coupled to perceptual variables such as lateral position and heading. In the 2nd, drivers pursued a virtual target in the scene. Both models yielded behavior that closely matches that of human drivers.     

Active steering along corrugated surfaces

A study is reported of the effect of dynamic occlusion that arises during locomotion over corrugated surfaces and its facilitating role on the control of locomotion, especially in cluttered environments. Surfaces varied in degree of corrugation and type of texture. Heading accuracy was assessed by having participants perform an active steering task. Results demonstrated the advantage of texture-mapped image surfaces over discrete element surfaces in the corrugated conditions. Observers appear to exploit accretion and deletion of optical texture at the occluding edge to extract and use information about heading direction for the control of movements in cluttered environments.     

Coordinated flexibility: how initial gaze position modulates eye-hand coordination and reaching

Reaching to targets in space requires the coordination of eye and hand movements. In two experiments, we recorded eye and hand kinematics to examine the role of gaze position at target onset on eye-hand coordination and reaching performance. Experiment 1 showed that with eyes and hand aligned on the same peripheral start location, time lags between eye and hand onsets were small and initiation times were substantially correlated, suggesting simultaneous control and tight eye-hand coupling. With eyes and hand departing from different start locations (gaze aligned with the center of the range of possible target positions), time lags between eye and hand onsets were large and initiation times were largely uncorrelated, suggesting independent control and decoupling of eye and hand movements. Furthermore, initial gaze position strongly mediated manual reaching performance indexed by increments in movement time as a function of target distance. Experiment 2 confirmed the impact of target foveation in modulating the effect of target distance on movement time. Our findings reveal the operation of an overarching, flexible neural control system that tunes the operation and cooperation of saccadic and manual control systems depending on where the eyes look at target onset.     

Eye movements during coincidence-anticipation performance

The present study related visual processing, as indicated by eye movements, to performance accuracy on coincidence-anticipation tasks. Three age groups were tested on a coincidence-anticipation task and their eye movements recorded. Three levels of response were administered under three levels of stimulus speed. A MANOVA indicated that both eye tracking and coincidence-anticipation varied among the age groups and with stimulus speed, although in different directions. Eye tracking error decreased with increasing age but only the coincidence-anticipation response accuracy of the youngest group appeared to be less accurate than that of the adults. Eye tracking error also decreased with decreasing stimulus speed but coincidence-anticipation performance was least accurate at the slow speed. Coincidence-anticipation error was the major contributor to performance differences with changes in the type of response.     

Effects of velocity and limb loading on the coordination between limb movements during walking

The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.5 km/hr) and limb loading on the coordination between arm and leg movements during treadmill walking in 7 participants. Both the consistency of the individual limb movements and the stability of their coordination increased with increasing velocity; the frequency coordination between arm and leg movements was 2:1 at the lower velocities and 1:1 at the higher velocities. The mass manipulation affected the individual limb movements but not their coordination, indicating that a stable walking pattern was preserved. The results differed qualitatively from those obtained in studies on bimanual interlimb coordination, implying that the dynamical principles identified therein are not readily applicable to locomotion.     

Involuntary Rotations of a Steering Device Induced by Voluntary Rotations of the Head and Maintained Eccentric Head Positions

In a series of 4 experiments, the authors examined involuntary rotations of a steering device (handlebar or wheel) that were associated with periodic head rotations and eccentric head positions. Periodic head rotations resulted in isodirectional involuntary rotations of a horizontally arranged steering device of very small amplitude. When the orientation of a steering wheel was changed to vertical and to a backward tilt, the involuntary rotations were in the opposite direction. That pattern of results is consistent with the assumption that small movements of the shoulder girdle, which are associated with head turns and which cannot be prevented by mechanical immobilization of the shoulder, are propagated to the wheel, but is not consistent with previous suggestions that involuntary rotations of a steering device can result from the action of the tonic neck reflex. Effects that correspond to the pattern of the tonic neck reflex were found only when a spring-centered handlebar was held in an eccentric position; maintenance of the eccentric position was facilitated when the participant's head was turned in the opposite direction. The findings strongly suggest that head movements can result in involuntary movements of a steering device via different mechanisms.     

Involuntary Rotations of a Steering Device Induced by Voluntary Rotations of the Head and Maintained Eccentric Head Positions

In a series of 4 experiments, the authors examined involuntary rotations of a steering device (handlebar or wheel) that were associated with periodic head rotations and eccentric head positions. Periodic head rotations resulted in isodirectional involuntary rotations of a horizontally arranged steering device of very small amplitude. When the orientation of a steering wheel was changed to vertical and to a backward tilt, the involuntary rotations were in the opposite direction. That pattern of results is consistent with the assumption that small movements of the shoulder girdle, which are associated with head turns and which cannot be prevented by mechanical immobilization of the shoulder, are propagated to the wheel, but is not consistent with previous suggestions that involuntary rotations of a steering device can result from the action of the tonic neck reflex. Effects that correspond to the pattern of the tonic neck reflex were found only when a spring-centered handlebar was held in an eccentric position; maintenance of the eccentric position was facilitated when the participant's head was turned in the opposite direction. The findings strongly suggest that head movements can result in involuntary movements of a steering device via different mechanisms.