Driving behaviour in adults with attention deficit/hyperactivity disorder.

BACKGROUND: Little is known about the impact of cognitive impairments on driving in adults with ADHD. The present study compared the performance of adults with and without ADHD in a driving simulator on two different routes: an urban route which we hypothesised would exacerbate weak impulse control in ADHD and a motorway route, to challenge deficits in sustained attention. METHODS: Adults with (n = 22, 16 males) and without (n = 21, 18 males) ADHD completed a simulated driving session while eye movement data were recorded simultaneously. Participants also completed the Manchester Driving Behaviour Questionnaire (DBQ) and the Conners Adult ADHD Rating Scale (CAARS). Measures of driving performance included average speed, proportion distance travelled over speed limit (speeding) and lane deviation. These variables and the eye movement measures (spread of fixations, mean fixation duration) were compared between groups and routes. Also, driving behaviours, including responses to programmed events, were categorised and the frequencies within categories were compared between groups. Finally, speech analysis was performed to compare emotional verbal expressions during driving between groups. RESULTS: ADHD participants reported significantly more Violations and Lapses on the DBQ than control participants and significantly more accidents. Average speed and speeding were also higher but did not interact with route type. ADHD participants showed poorer vehicle control, greater levels of frustration with other road users (including greater frequencies of negative comments) and a trend for less safe driving when changing lanes/overtaking on the motorway. These effects were predicted by hyperactive/impulsive CAARS scores. They were also more likely to cause a crash/near miss when an event occurred on the urban route. CONCLUSIONS: The results suggest that difficulty regulating and controlling impulsive behavior, reflected in speeding, frustration with other road users, less safety when changing lanes on the motorway and a greater likelihood of an accident following an unexpected event, underlie impaired driving in ADHD. Hyperactivity/impulsivity symptoms correlated with these indices. Deficits in sustained attention seemed to play a lesser role in this particular study, although further research is needed to determine whether effects on attention emerge over longer periods of time and/or are influenced by the novelty of the simulator environment.

Improving attitudes towards vulnerable road users.

Some car drivers pass vulnerable road users (VRUs) at too high a speed and leave too little gap. Research suggests that out-group bias and a lack of empathy may relate to these dangerous incidents. To address this problem, four road safety videos were created with the aim of increasing car drivers' empathy toward Vulnerable Road Users (VRUs). Each video focused on the back-story of a VRU (two horse riders and two cyclists), with a predominantly persuasive approach to inducing empathy and reducing out-group bias. The effectiveness of the videos on car drivers' immediate implicit and explicit attitudes, and on their future intended behaviour around these VRUs, was assessed by comparing intervention participants' responses with those of control participants, both before and after the intervention. Explicit attitudes towards horse riders improved following the intervention for drivers who saw the horse rider videos compared to a control group. The horse rider videos did not however improve explicit attitudes toward cyclists. Similarly, those participants who saw the cyclist videos showed improved attitudes towards cyclists but not horse riders. An Implicit Attitude Test (IAT) found no implicit biases for or against horse riders or cyclists, either before or after the intervention. Intended future passing behaviour was affected by the intervention however, with car drivers reporting greater intended passing distances and lower passing speeds compared to the control group. The results suggest that safety campaigns that adopt this approach can change attitudes and intended behaviours towards VRUs.

Dimensions of Self-Reported Driving Difficulty in Autistic and Non-Autistic Adults and their Relationship with Autistic Traits.

A survey asked autistic and non-autistic people about the driving difficulties they experience and their autistic traits. Principle components analysis was used to identify how reported difficulties clustered together in each group, and regression was used to determine which subscales of the Autism Spectrum Quotient predict these factors. For autistic drivers three factors of driving difficulty emerged: a Driving Executive factor, predicted by Attention Switching; a Driving Understanding factor, predicted by Communication; and a Driving Social Interaction factor, predicted by Attention Switching. For non-autistic drivers only one Driving General factor emerged, predicted by Communication. This suggests autistic people may experience at least three distinct domains of difficulty when driving which may relate to their particular profile of autistic features.

A novel driving assessment combining hazard perception, hazard prediction and theory questions.

A new hazard test was created using high-fidelity computer animation containing ten hazards. Sixty learner drivers and sixty experienced drivers sat either a hazard-perception version of this test (requiring timed responses to materialized hazards) or a hazard-prediction variant of the test (where the screen is occluded as the hazard begins to appear and drivers are asked 'What happens next?'). Recent studies have demonstrated that the prediction test format outperforms the hazard perception format using naturalistic video, but there has not yet been a study replicating this effect with computer-animated materials similar to the quality of those used in the official UK hazard perception test. The new test also included eleven theory questions designed to probe drivers' knowledge of the rules of the road. The results demonstrated that both test variants differentiated between driver groups with considerable effect sizes. Theory-question scores were comparable across learner and experienced driver groups, reflecting learners' preparation for the test and possible issues with memory decay and overwriting in the experienced group. As an interesting aside, driving-related video game play negatively correlated with hazard perception performance, but not with hazard prediction scores. Some individual hazards better suited the prediction or perception test format, raising the possibility of a future hybrid test that combines the two approaches.

Attentional Differences in a Driving Hazard Perception Task in Adults with Autism Spectrum Disorders.

The current study explored attentional processing of social and non-social stimuli in ASD within the context of a driving hazard perception task. Participants watched videos of road scenes and detected hazards while their eye movements were recorded. Although individuals with ASD demonstrated relatively good detection of driving hazards, they were slower to orient to hazards. Greater attentional capture in the time preceding the hazards' onset was associated with lower verbal IQ. The findings suggest that individuals with ASD may distribute and direct their attention differently when identifying driving hazards.

Attraction and distraction of attention with roadside advertisements.

The optimum positioning of roadside advertisements is recognized by the industry as an important factor in attracting the attention of passing drivers. Less acknowledged is the possibility that the location of an advertisement may distract attention from vital driving-related information. This study compared street-level advertisements (SLAs; predominantly bus shelters) with raised-level advertisements (RLAs) of the same size that were suspended 3 m above the ground, on their ability to attract attention under different task conditions. Participants were split into two groups and watched video clips of driving, rating them for hazardousness while their eye movements were recorded. One of the groups was additionally primed to attend to advertisements. SLAs received the most fixations when participants were solely looking for hazards, and the fewest fixations when primed to look for advertisements. Though SLAs also had longer fixations than the RLAs, they were more poorly recognized in a subsequent memory test. We conclude that SLAs attract and hold attention at inappropriate times compared to raised-level advertisements.

Saccadic latency as a function of target duration in a spatial localization task.

This study examined a potential confound in the inverse relationship between target duration and saccadic latency reported by Adam, Ketelaars, Kingma, and Hoek in 1993. Eight participants located a briefly flashed target by moving the eyes and the cursor toward its position in a (backward) mask condition and in a no-mask condition. Analysis showed similar saccadic latencies in both conditions, thereby refuting the potentially confounding role of the backward masking procedure. It is tenatively suggested that the longer saccadic latencies noted for shorter target durations may be associated with delayed accumulation of evidence for the detection of the target.

Manipulating saccadic decision-rate distributions in visual search.

The Gaussian shape of reciprocal latency distributions typically found in single saccade tasks supports the idea of a race-to-threshold process underlying the decision when to saccade (R. H. Carpenter & M. L. Williams, 1995). However, second and later saccades in a visual search task revealed decision-rate (=reciprocal latency) distributions that were skewed Gamma-like (E. M. Van Loon, I. T. Hooge, & A. V. Van den Berg, 2002). Here we consider a related family of Beta-prime distributions that follows from strong competition with a signal to stop the sequence, and is described by two parameters: a fixate and saccade threshold. In three saccadic search experiments, we tried to manipulate the two thresholds independently, thereby expecting change in shape and mean of the reciprocal latency distribution. Interestingly, rate distributions for later saccades were significantly better fit by Beta-prime than by Gamma functions. Increases in the distribution's skew were found with higher display density, but only for second and later saccades. First saccade rate distributions were not altered by the expected target location or by visual information presented prior to the search, but making pre-search saccades did influence both thresholds. The mean rate remained a stereotyped function of ordinal position in the saccade sequence. Our results support strong competition between two decision signals underlying the timing of saccades.

Motorcycling experience and hazard perception.

Studies of hazard perception skills in car drivers suggest that the ability to spot hazards improves with driving experience. Is this the case with motorcyclists? Sixty-one motorcyclists, split across three groups (novice, experienced and advanced riders) were tested on a hazard perception test containing video clips filmed from the perspective of a motorcyclist. Response times to hazards revealed that the advanced riders (who had completed an advanced riding course) were the fastest, and the experienced riders were the slowest to respond to hazards, with novice riders falling in-between. Advanced riders were also found to make more internal attributions regarding the causes of the hazards than novice riders (though on a general measure of Locus of Control there was no difference between groups). The results demonstrate a link between advanced training and motorcycling hazard perception skill, but raise important concerns about the effects of mere experience on rider safety. This challenges previous conceptions that simply extrapolated from our understanding of the hazard perception skills of car drivers to this particularly vulnerable group of road users.

Attending overtaking cars and motorcycles through the mirrors before changing lanes.

Right of way violation crashes are the most common type of accidents that motorcyclists face. This study assessed right of way decisions in scenarios which require noticing whether there is traffic from behind that is about to overtake. A test was created which presents participants clips with a wide field of vision (from a driver's perspective in a moving vehicle), with mirror information inset that allows either cars or motorcycles that are about to overtake, to be attended. Novice and experienced car drivers, and dual drivers (with both car and motorcycle experience), watched these clips while their eye movements were monitored. The results indicated that in the rear-view and the right-side mirrors, and in the right hand lane, conflicting motorcycles garnered more attention than conflicting cars. This pattern however was particularly driven by the dual drivers group. Additionally, novice drivers and dual drivers made more use of the right side mirror than the experienced drivers. Dual drivers also made more use of the rear view mirror than experienced drivers. Finally, significant positive correlations that were found between percentages of safe manoeuvres and measures of visual search provide direct evidence demonstrating that the frequency of risky manoeuvres was indeed larger in those cases where less time was spent gazing at the mirrors, indicating that the additional attention devoted to process conflicting vehicles contributes to reduce risky manoeuvres. The general pattern of results also provides some indirect support that non-motorcyclists drivers are more likely to have Look But Fail To See errors with conflicting motorcycles than motorcyclist drivers.

Some hazards are more attractive than others: drivers of varying experience respond differently to different types of hazard.

The ability to detect hazards in video clips of driving has been inconsistently linked to driving experience and skill. One potential reason for the lack of consistency is the failure to understand the structural differences between those hazards that discriminate between safe and unsafe drivers, and those that do not. The current study used a car simulator to test drivers of differing levels of experience on approach to a series of hazards that were categorized a priori according to their underlying structure. The results showed that learner drivers took longer to fixate hazards, although they were particularly likely to miss hazards that were obscured by the environment (such as a pedestrian emerging from behind a parked truck). While drivers with a moderate amount of experience were as fast as driving instructors to look at hazards, they spent the greatest amount of time looking at them. Only instructors' ability to detect hazards early in the approach translated into differences in driving speed for certain types of hazard. The results demonstrate that drivers of varying experience respond differently to different hazards, and lay the foundations for a hazard typology.

Decisions about objects in real-world scenes are influenced by visual saliency before and during their inspection.

Evidence from eye-tracking experiments has provided mixed support for saliency map models of inspection, with the task set for the viewer accounting for some of the discrepancies between predictions and observations. In the present experiment viewers inspected pictures of road scenes with the task being to decide whether or not they would enter a highway from a junction. Road safety observations have concluded that highly visible road users are less likely to be involved in crashes, suggesting that saliency is important in real-world tasks. The saliency of a critical vehicle was varied in the present task, as was the type of vehicle and the preferred vehicle of the viewer. Decisions were influenced by saliency, with more risky decisions when low saliency motorcycles were present. Given that the vehicles were invariably inspected, this may relate to the high incidence of "looked-but-failed-to-see" crashes involving motorcycles and to prevalence effects in visual search. Eye-tracking measures indicated effects of saliency on the fixation preceding inspection of the critical vehicle (as well as effects on inspection of the vehicle itself), suggesting that high saliency can attract an early fixation. These results have implications for recommendations about the conspicuity of vulnerable road users.

Visual strategies used for time-to-arrival judgments in driving.

To investigate the sources of visual information that are involved in the anticipation of collisions we recorded eye movements while participants made relative timing judgments about approaching vehicles at a junction. The avoidance of collisions is a critical aspect in driving, particularly where cars enter a line of traffic from a side road, and the present study required judgments about animations in a virtual driving environment. In two experiments we investigated the effects of (i) the angle of approach of the vehicle and the type of path (straight or curved) of the observer, and (ii) the speed of both the observer and the approaching car. Relative timing judgments depend on the angle of approach of the other vehicle (judgments are more accurate for perpendicular than for obtuse angles). Eye-movement analysis shows that visual strategies in relative timing judgments are characterised by saccadic eye movements back and forth between the approaching car and the road ahead, particularly the side line which may serve as a spatial reference point. Results suggest that observers use the distance of the car from this reference point for their timing judgments.

Commentary training improves responsiveness to hazards in a driving simulator.

Can commentary driving produce safer drivers? Producing a verbal commentary of potential hazards during driving has long been considered by the police to improve hazard perception skills. In this study we investigated whether learner drivers would benefit from being trained to produce a commentary drive. All learners were initially assessed on a virtual route in a driving simulator that contained 9 hazards. One group of drivers was then trained in commentary driving, and their subsequent simulated driving behaviour was compared to a control group. The results showed that the trained group had fewer crashes, reduced their speed sooner on approach to hazards, and applied pressure to the brakes sooner than untrained drivers. Conversely the untrained drivers' behaviour on approach to hazards was symptomatic of being surprised at the appearance of the hazards. The benefit of training was found to be greater for certain types of hazard than others.

Brief report: driving hazard perception in autism.

This study investigated whether individuals with ASD (autistic spectrum disorders) are able to identify driving hazards, given their difficulties processing social information, Klin et al. (Archives of General Psychiatry 59: 809-816, 2002). Twenty-three adult males with ASD and 21 comparison participants viewed 10 video clips containing driving hazards. In half of the clips the source of the hazard was a visible person (social); in the other half the source was a car (non-social). Participants with ASD identified fewer social hazards than the comparison participants (U = 163.00, N = 44, p < .05) but not non-social. Participants with ASD were also slower to respond than comparison participants, F(1,40) = 4.93, p < .05. This suggests that, although people with ASD can perceive driving hazards they may have specific difficulty identifying them if they involve a person.

Eye fixation scanpaths of younger and older drivers in a hazard perception task.

Our previous research has shown that observing patterns of eye fixations is a successful method of establishing differences in underlying cognitive processes between groups of drivers. Eye movements recorded from drivers in a laboratory while they watch film clips recorded from a driver's perspective can be used to identify scanpaths and search patterns that reveal ability differences. In the present study 12 older subjects (60-75 years) and 12 younger subjects (30-45 years) watched clips for potential hazards such as other road users appearing on an intersecting trajectory. Acuity and visual field differences between the two groups were eliminated through screening, so that only age-related differences would emerge. Eye fixations were analysed on a frame-by-frame basis to generate sequences of codes representing the location and object of the viewer's interest, before and during the appearance of a hazard. These codes were analysed for the existence of two fixation scanpaths using Markov Matrices. Unique scanpaths were identified for each group of drivers before and during the hazard. Evidence from the inspection of different objects and from the spread of the search indicated that both groups of driver were sensitive to attentional capture by the appearance of the hazard. Detection of the hazards - both speed and accuracy - was similar for older and younger drivers, although the older drivers perceived the films as being more hazardous in general. There is little evidence in this study of an age-related decline in the search of the scene when detecting hazards.