Characterisation of motorway driving style using naturalistic driving data

The study of measurable differences between drivers has ramifications for several sub-fields in traffic and transportation research. Better understanding of the variability in individual driving styles would be especially useful for understanding driver preferences, psychological mechanisms for vehicle control and for developing more realistic traffic simulations. In our study based on a large naturalistic data set, we investigated the driving style of 76 individuals driving in a motorway setting. We discovered that the majority of between-driver variation in keeping longitudinal and lateral safety margins, lane changing frequency, acceleration and speed preference, can be reduced to two dimensions, which we interpret as habitualised motives centred around mental effort and expediency.     

Perception of visual inclination in a real and simulated urban environment

The perceived inclination of slopes is generally overestimated. We claim that overestimation depends on the use of impoverished stimuli and on the distance between the observer and an inclined surface. In experiment 1, participants reported the perceived inclination of a set of urban roads from two different viewing distances. Observers did not overestimate the perceived inclination of slopes when they saw roads from the shorter viewing distances, whereas they slightly overestimated the perceived inclination of slopes from the farther distance. In experiment 2, participants reported the perceived inclination of a set of stereoscopic slides representing the same urban roads as in experiment 1. Here, observers did not overestimate the perceived inclination of slopes when the projected stereoscopic image contained horizontal disparity and simulated the shorter viewing distance; while they revealed a slight overestimation from the farther distance. We found always overestimation when the binocular image did not contain horizontal disparity, independently from the viewing distance. In conclusion, slopes are overestimated when (a) horizontal disparity is absent, and (b) the viewing distance is increased.     

Cell phone-induced failures of visual attention during simulated driving

This research examined the effects of hands-free cell phone conversations on simulated driving. The authors found that these conversations impaired driver's reactions to vehicles braking in front of them. The authors assessed whether this impairment could be attributed to a withdrawal of attention from the visual scene, yielding a form of inattention blindness. Cell phone conversations impaired explicit recognition memory for roadside billboards. Eye-tracking data indicated that this was due to reduced attention to foveal information. This interpretation was bolstered by data showing that cell phone conversations impaired implicit perceptual memory for items presented at fixation. The data suggest that the impairment of driving performance produced by cell phone conversations is mediated, at least in part, by reduced attention to visual inputs.     

A psychophysiological and driving performance evaluation of focal and ambient visual processing demands in simulated driving

Research has focused little on the ambient and focal visual channels within which driving and side-task information can be processed. In the current experiment, for the purpose of demonstrating differentiation of focal and ambient visual processing attentional demands on driving performance and physiological response, subjects participated in a dual-task driving simulation that contained focal and ambient components. We hypothesized that ambient demands would not have any effects on driving performance or physiological response, whereas the focal-side-task would cause a deterioration in driving performance and specific changes in physiological response. Support for these hypotheses would provide evidence that focal visual processing is attention demanding, whereas the processing of ambient visual information is not.Some results suggest that ambient visual information was processed pre-attentively, whereas focal visual information requires attentional resources to be processed. Driving performance deteriorated and changes in physiological response occurred when the focal side-task was added to driving, but not when the ambient side-task was added. However, we failed to see predicted changes in driving performance and physiological response as the demands of the focal and ambient components of the driving simulation varied. The results of the current study suggest that a differentiation in attention demands between focal and ambient vision does exist, but that further research is needed to better understand the nature and practical consequences of the differentiation.     

Multidimensional mapping of visual space with real and simulated stars

In each of five experiments Ss made direct assessments of interpoint distances within a stimulus configuration. A multidimensional scaling method was applied to make explicit the form of the subjective configuration. The stimulus configurations consisted of small light points arranged in a two- or three-dimensional array in a dark room, and of real stars in the sky. All the data were adequately accounted for by a configuration constructed in Euclidean space of the appropriate dimensionality. That was true even in the situation where alley experiments with the same Ss gave the result that is usually regarded as evidence for a hyperbolic binocular space. The Euclidean interpretation entails a more complicated form of correspondence between physical and visual spaces than the hyperbolic interpretation.     

Allocation of visual attention while driving with simulated augmented reality

Augmented reality (AR) technologies aim to optimize the visual attention of the driver by increasing the salience of high value elements. In such systems, ‘value’ is typically seen as linked to the general activity of driving, but not manoeuvres. However, several studies have shown that during activity, eye movements are specific to the immediate goal. In our experiment, 48 participants watched videos of automobile driving situations, during which they had to make decisions. In these videos, some situational cues were graphically highlighted. Depending on the experimental group, highlighted cues related to either the general driving task (e.g. road signs, pedestrians) or to a specific manoeuvre (e.g. look for overtaking cars before changing the lane). The results show that AR impacts the allocation of visual attention more strongly during the decision-making phase. In all AR conditions, the ability to extract information is less efficient. In particular, highlighting (by AR) general cues does not affect the detection of cues related to a manoeuvre, but it does change the allocation of visual attention: fixations are more numerous and less task-specific.     

Effects of manual versus voice-activated dialing during simulated driving

We measured driving performance (lane-keeping errors, driving times, and glances away from the road scene) in a video driving simulator for 24 volunteers who each drove alone on a 10.6-km multicurved course while simultaneously placing calls on a mobile phone subscribed to a voice-activated dialing system. Driving performance also was measured for the same distance while participants manually dialed phone numbers and while they drove without dialing. There were 22% fewer lane-keeping errors (p<.01) and 56% fewer glances away from the road scene (p<.01) when they used voice-activated dialing as compared to manual dialing. Significantly longer driving times in both of the dialing conditions as compared to the No Dialing condition are discussed in terms of the hypothesis that drivers decrease driving speed to compensate for the demands of the secondary phone tasks.     

Effects of distraction and experience on situation awareness and simulated driving

This study examined the impact of cell phone conversation on situation awareness and performance of novice and experienced drivers. Driving performance and situation awareness among novice drivers ages 14–16 (n = 25) and experienced drivers ages 21–52 (n = 26) were assessed using a driving simulator. Performance was measured by the number of driving infractions committed: speeding, collisions, pedestrians struck, stop signs missed, and centerline and road edge crossings. Situation awareness was assessed through a query method and through participants’ performance on a direction-following task. Cognitive distractions were induced through simulated hands-free cell phone conversations. The results indicated that novice drivers committed more driving infractions and were less situationally aware than their experienced counterparts. However, the two groups suffered similar decrements in performance during the cell phone condition. This study provides evidence of the detrimental effects of cell phone use for both novice and experienced drivers. These findings have implications for supporting driving legislation that limits the use of cell phones (including hands-free) in motor vehicles, regardless of the driver’s experience level.     

Effects of memory load on visual search

It remains unclear how memory load affects attentional processes in visual search (VS). No effects, as well as beneficial and detrimental effects of memory load, have been found in this type of task. The main goal of the present research was to explore whether memory load has a modulating effect on VS by means of a different attentional set induced by the order of trials (mixed vs. blocked) and by the time presentation of visual display (long vs. short). In Experiment 1, we randomized the order of type of trial (5, 10 and 15 items presented in the display) while it remained constant (10 items) in Experiments 2A and 2B. In the later experiments, we also changed time presentation of visual display (3000 vs. 1300 ms, respectively). Results showed no differential effects of memory load in Experiments 1 and 2A, but they showed up in Experiment 2B: RTs were longer in the attentional task for trials under high memory load conditions. Although our hypothesis of the attentional set is supported by the results, other theoretical implications are also worth discussing in order to better understand how memory load may modulate attentional processes in VS.     

Looking and thinking when driving: The impact of gaze and cognitive load on steering

Driving around bends at high speeds is a task performed by many on a daily basis but the underlying mechanisms of steering control remain largely unknown. Previous research has shown that when steering, gaze direction can be a critical component of success. However, with increased use of in-vehicle information systems (IVIS), there is growing competition over the same resources that are needed to steer (gaze as well as associated attentional resources). Although it can be argued that locomotor steering is an automatic task that can be performed without recourse to conscious “cognitive” control, much simpler locomotor-related tasks, such as judging one’s heading, have been shown to be affected by concurrent attentional tasks (Wann, Swapp, & Rushton, 2000). Here we examined whether an attentional task placed at an offset fixation point influenced concurrent steering performance along a computer simulated road. The experiments either used gaze-fixation points that had similar properties to real-world road signs (i.e. moved relative to the vehicle) or were more akin to IVIS (i.e. fixed to the vehicle). Results showed that gaze fixation eccentric to future path caused systematic steering biases. The degree or type of cognitive load did not change the degree of steering bias, but there was some evidence of decreased lane variability when viewing the IVIS-type displays. No differences in steering performance were found between the different types of cognitive task. We conclude that where you look is critical for safe driving, and IVIS-type displays might make drivers more susceptible to cognitive interference.     

Impact of simulated visual impairment on the cognitive test performance of young adults

Aims. This study investigated the effect of simulated visual impairment on the speed and accuracy of performance on a series of commonly used cognitive tests. Methods. Cognitive performance was assessed for 30 young, visually normal subjects (M=22.0±3.1 years) using the Digit Symbol Substitution Test (DSST), Trail Making Test (TMT) A and B and the Stroop Colour Word Test under three visual conditions: normal vision and two levels of visually degrading filters (Vistech^TM) administered in a random order. Distance visual acuity and contrast sensitivity were also assessed for each filter condition. Results. The visual filters, which degraded contrast sensitivity to a greater extent than visual acuity, significantly increased the time to complete (p<.05), but not the number of errors made, on the DSST and the TMT A and B and affected only some components of the Stroop test. Conclusions. Reduced contrast sensitivity had a marked effect on the speed but not the accuracy of performance on commonly used cognitive tests, even in young individuals; the implications of these findings are discussed.     

Working memory load and distraction: dissociable effects of visual maintenance and cognitive control

We establish a new dissociation between the roles of working memory (WM) cognitive control and visual maintenance in selective attention as measured by the efficiency of distractor rejection. The extent to which focused selective attention can prevent distraction has been shown to critically depend on the level and type of load involved in the task. High perceptual load that consumes perceptual capacity leads to reduced distractor processing, whereas high WM load that reduces WM ability to exert priority-based executive cognitive control over the task results in increased distractor processing (e.g., Lavie, Trends in Cognitive Sciences, 9(2), 75–82, 2005). WM also serves to maintain task-relevant visual representations, and such visual maintenance is known to recruit the same sensory cortices as those involved in perception (e.g., Pasternak & Greenlee, Nature Reviews Neuroscience, 6(2), 97–107, 2005). These findings led us to hypothesize that loading WM with visual maintenance would reduce visual capacity involved in perception, thus resulting in reduced distractor processing—similar to perceptual load and opposite to WM cognitive control load. Distractor processing was assessed in a response competition task, presented during the memory interval (or during encoding; Experiment 1a) of a WM task. Loading visual maintenance or encoding by increased set size for a memory sample of shapes, colors, and locations led to reduced distractor response competition effects. In contrast, loading WM cognitive control with verbal rehearsal of a random letter set led to increased distractor effects. These findings confirm load theory predictions and provide a novel functional distinction between the roles of WM maintenance and cognitive control in selective attention.     

Repeated usage of a motorway automated driving function: Automation level and behavioural adaption

The user’s perspective on highly automated driving systems is mostly studied during first contact/single usage. However, with repeated usage, acceptance and usage of automated driving systems might change. For advanced driving assistance systems, change with growing system usage is studied as behavioural adaptation. This concept of behavioural adaptation is applied to highly automated driving systems. In a driving simulator study, N = 61 drivers used an automated driving system for motorways during six experimental sessions. The drivers were free to activate / deactivate the function as they liked and to spend driving time on self-chosen side tasks. Automation level was varied as a between-subject factor (L3 vs. L4). Results show a more positive evaluation of the L4 system and behavioural adaptation for both levels over the course of the six sessions. For most aspects, behavioural adaptation is independent of system level (e.g., for system evaluation, distribution of attention). Only for drivers’ reaction to requests to intervene, a strong impact of system level on the occurrence behavioural adaption can be found. The results are discussed with regard to the theory of behavioural adaptation.     

Alteration of the useful visual field as a function of state of vigilance in simulated car driving

The size of the useful visual field varies under the effect of different variables. Recent research has shown that the useful visual field deteriorates when the individual carries out a monotonous and prolonged monitoring task that leads to drowsiness. The aim of this study was to establish if the visual field also deteriorates during simulated car driving when this may induce a decrease in the level of alertness. Eighteen subjects had to follow another vehicle for 2 h while simultaneously carrying out a colour discrimination task in central vision and a detection task of a peripheral target that could appear anywhere in the road scene. The analysis of the data indicated that the useful visual field deteriorates with the prolongation of the monotonous driving task according to a tunnel vision-like phenomenon.     

Mental load and loss of control over speed in real driving.: Towards a theory of attentional speed control

Relationships between attention and speed control are analysed. The demands of speed control are derived from subjective appreciation of the traffic environment and from the need to adapt to legal restrictions. Drivers check the speedometer more or less frequently and also use their subjective speed perception while looking ahead. It is hypothesised that, in absence of specific speed restrictions, drivers choose an optimum preferred speed so that the attentional effort dedicated to speed control is minimised but with explicit speed restrictions additional resources are required to keep speed under control including more glances to the speedometer. If a secondary task needs attention the speed control is affected and the speed tends to return to the optimal preferred level. Twelve participants drove about 200 km in a Spanish highway under eight conditions: two speedometer states (visible/concealed) × two speed instructions (free/restricted between 90 and 100 km/h) × two workload states (normal driving/performing a mental task). The results demonstrated: (a) that under free speed the drivers choice was 11 km/h faster than in the restricted-speed condition, indicating that the speed instructions were effective and operated as a speed limit. (b) When a mental task was performed the speed increased independently of the speedometer availability under restricted speed but not in the free speed condition, what clearly supports the stated hypothesis. The role of the speedometer in speed control, its relations with endogenous distraction and its implications for driving are analysed.     

Task-induced fatigue states and simulated driving performance

States of fatigue are implicated in driver impairment and motor vehicle accidents. This article reports two studies investigating two possible mechanisms for performance impairment: (1) loss of attentional resources; and (2) active regulation of matching effort to task demands. The first hypothesis predicts that fatigue effects will be accentuated by high task demands, but the second hypothesis predicts that fatigue effects will be strongest in "underload" conditions. In two studies, drivers performed a stimulated driving task, in which task demands were manipulated by varying road curvature. In a "fatigue induction" condition, the early part of the drive was occupied by performance of a demanding secondary task concurrently with driving, after which the concurrent task ceased. Post-induction driving performance was compared with a control condition in which drivers were not exposed to the induction. In both studies, the fatigue induction elicited various subjective fatigue and stress symptoms, and also raised reported workload. Fatigue effects on vehicle control and signal detection were assessed during and after the fatigue induction. The fatigue induction increased heading error, reduced steering activity, and, in the second study, reduced perceptual sensitivity on a secondary detection task. These effects were confined to driving on straight rather than on curved road sections, consistent with the effort regulation hypothesis. The second study showed that fatigue effects were moderated by a motivational manipulation. Results are interpreted within a control model, such that task-induced fatigue may reduce awareness of performance impairment, rather than reluctance or inability to mobilize compensatory effort following detection of impairment.     

Effects of hands-free cellular phone conversational cognitive tasks on driving stability based on driving simulation experiment

Driver distraction due to cellular phone usage is a major contributing factor to road crashes. This study compares the effects of conversational cognitive tasks using hands-free cellular phone on driving performance under three distraction conditions: (1) no distraction (no cellular conversation), (2) normal conversation (non-emotional cellular conversation), and (3) seven-level mathematical calculations. A car-following scenario was implemented using a driving simulator. Thirty young drivers with an average age of 24.1 years maintained a constant speed and distance between the subject vehicle and a leading vehicle on the driving simulator, and then respond to the leading vehicle’s emergency stop. The driving performances were assessed by collecting and statistically analyzing several variables of maneuver stability: the drivers’ brake reaction times, driving speed fluctuation, car-following distance undulation, and car-following time-headway undulation. The results revealed that normal conversation on a hands-free cellular phone impaired driving performance. The degree of impairment caused by normal calculation was equivalent to the distraction caused by Level 3 mathematical calculations according to the seven-level calculation baseline. The calculation difficulty of Level 3 is one double-digit figure plus a single-digit figure, and non-carry addition mental arithmetic is required, e.g., 44 + 4. The results indicated that an increase in the level of complexity of the calculation task was associated with an increase in brake reaction time. The seven-level calculation-task baseline could be applied to measure additional distraction effects on driving performance for further comparison.     

Multimedia instructions and cognitive load theory: Effects of modality and cueing

Background: Recent research on the influence of presentation format on the effectiveness of multimedia instructions has yielded some interesting results. According to cognitive load theory (Sweller, Van Merriënboer, & Paas, 1998) and Mayer's theory of multimedia learning (Mayer, 2001), replacing visual text with spoken text (the modality effect) and adding visual cues relating elements of a picture to the text (the cueing effect) both increase the effectiveness of multimedia instructions in terms of better learning results or less mental effort spent. Aims: The aim of this study was to test the generalisability of the modality and cueing effect in a classroom setting. Sample: The participants were 111 second‐year students from the Department of Education at the University of Gent in Belgium (age between 19 and 25 years). Method: The participants studied a web‐based multimedia lesson on instructional design for about one hour. Afterwards they completed a retention and a transfer test. During both the instruction and the tests, self‐report measures of mental effort were administered. Results: Adding visual cues to the pictures resulted in higher retention scores, while replacing visual text with spoken text resulted in lower retention and transfer scores. Conclusions: Only a weak cueing effect and even a reverse modality effect have been found, indicating that both effects do not easily generalise to non‐laboratory settings. A possible explanation for the reversed modality effect is that the multimedia instructions in this study were learner‐paced, as opposed to the system‐paced instructions used in earlier research.     

Effects of vision and cognitive load on anticipatory and compensatory postural control

This study assessed the effects of vision and cognitive load on anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) in response to an externally triggered postural perturbation. A ball-hitting test was repeated under different visual conditions (eyes open, EO; eyes closed, EC) and cognitive loads (no load, 3-subtraction task, time-limited 3-subtraction task). Data were collected separately for I) surface electromyography from the right side of the biceps brachii (BIC) and erector spinae (ES) to detect the latency and response intensity (RI); and II) displacement of the centre of pressure (ΔCOP) to detect the standard deviation (ΔCOP_SD) and maximum value (ΔCOP_max) in the anterior-posterior direction. Compared with the results under the EC condition, the ES latency was shorter and the RI of the BIC was lower under the EO condition. Accordingly, the ΔCOP_SD and ΔCOP_max were increased in the APAs phase and decreased in the CPAs phase. Cognitive load had no effect on APAs and CPAs or on ΔCOP in the APAs phase. However, ΔCOP_max was decreased in the CPAs phase during the EC condition. In conclusion, vision played an important role in APAs and CPAs for muscle activation and ΔCOP. Cognitive load had no effect on neuromuscular APAs or CPAs except when the postural perturbation occurred when visually unexpected.