Visual motion perception predicts driving hazard perception ability

Driving safety: Investigating the cognitive foundations of accident prevention

Driving is a crucial aspect of personal independence, and accurate assessment of driving skills is vital for ensuring road safety. This study aimed to identify reliable cognitive predictors of safe driving through a driving simulator experiment. We assessed the driving performance of 66 university students in two distinct simulated driving conditions and evaluated their cognitive skills in decision-making, attention, memory, reasoning, perception, and coordination. Multiple regression analyses were conducted to determine the most reliable cognitive predictor of driving outcome. Results revealed that under favorable driving conditions characterized by good weather and limited interactions with other road users, none of the variables tested in the study were able to predict driving performance. However, in a more challenging scenario with adverse weather conditions and heavier traffic, cognitive assessment scores demonstrated significant predictive power for the rate of traffic infractions committed. Specifically, cognitive skills related to memory and coordination were found to be most predictive. This study underscores the significance of cognitive ability, particularly memory, in ensuring safe driving performance. Incorporating cognitive evaluations in driver licensing and education/training programs can enhance the evaluation of drivers' competence and promote safer driving practices.

The impact of patient-reported visual disturbance on dynamic visual acuity in myopic patients after corneal refractive surgery

Purpose

To investigate the impact of patient-reported visual disturbance on dynamic visual acuity in myopic patients after corneal refractive surgery.

Methods

This is a prospective nonrandomized study. Adult myopic patients receiving bilateral laser-assisted sub-epithelial keratomileusis (LASEK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or small incision lenticule extraction (SMILE) with Plano target were included. Eight types of patient-reported visual disturbance were evaluated regarding frequency, severity and bothersome and dynamic visual acuity (DVA) of 40 and 80 degrees per second (dps) was measured postoperatively at 3 months.

Results

The study enrolled 95 patients with an average age of 27.6 ± 6.4 years. The most frequently reported visual disturbance was the fluctuation in vision (70.5%), followed by glare (66.3%) and halo (57.4%). Postoperative DVA at 80 dps was significantly associated with the total score of haloes (p = 0.038) and difficulty in judging distance (p = 0.046). Significant worse postoperative DVA at 40 dps was observed in patients with haloes than those without (p = 0.024). The DVA at 80 dps for patients without haloes or difficulty in judging distance was significantly better than that with the symptoms (haloes, p = 0.047; difficulty in judging distance, p = 0.029). Subgroup analysis by surgical procedures demonstrated that the significant difference in DVA between patients with and without visual disturbance was only observed in patients receiving FS-LASIK.

Conclusion

Postoperatively, myopic patients undergoing corneal refractive surgery with haloes or difficulty in judging distance have significantly worse low and high-speed DVA than those without the symptoms. The present study provided the basis for postoperative guidance in daily tasks involving dynamic vision when patients have visual disturbances.

The relationship between central and mid-peripheral motion perception and the hazard perception test in younger and older adults

INTRODUCTION

Vision standards for driving are typically based on visual acuity, despite evidence that it is a poor predictor of driving safety and performance. However, visual motion perception is potentially relevant for driving, as the vehicle and surroundings are in motion. This study explored whether tests of central and mid-peripheral motion perception better predict performance on a hazard perception test (HPT), which is related to driving performance and crash risk, than visual acuity. Additionally, we explored whether age influences these associations, as healthy ageing impairs performance on some motion sensitivity tests.

METHODS

Sixty-five visually healthy drivers (35 younger, mean age: 25.5; SD 4.3 years; 30 older adults, mean age: 71.0; SD 5.4 years) underwent a computer-based HPT, plus four different motion sensitivity tests both centrally and at 15° eccentricity. Motion tests included minimum displacement to identify motion direction (Dmin ), contrast detection threshold for a drifting Gabor (motion contrast), coherence threshold for a translational global motion stimulus and direction discrimination for a biological motion stimulus in the presence of noise.

RESULTS

Overall, HPT reaction times were not significantly different between age groups (p = 0.40) nor were maximum HPT reaction times (p = 0.34). HPT response time was associated with motion contrast and Dmin centrally (r = 0.30, p = 0.02 and r = 0.28, p = 0.02, respectively) and with Dmin peripherally (r = 0.34, p = 0.005); these associations were not affected by age group. There was no significant association between binocular visual acuity and HPT response times (r = 0.02, p = 0.29).

CONCLUSIONS

Some measures of motion sensitivity in central and mid-peripheral vision were associated with HPT response times, whereas binocular visual acuity was not. Peripheral testing did not show an advantage over central testing for visually healthy older drivers. Our findings add to the growing body of evidence that the ability to detect small motion changes may have potential to identify unsafe road users.

The impact of different corneal refractive surgeries on binocular dynamic visual acuity

Purpose

To investigate the influence of different corneal refractive surgeries on dynamic visual acuity (DVA), and explore its potential influence factors.

Methods

This was a prospective non-randomized study. Adult myopic patients undergoing bilateral laser-assisted sub-epithelial keratomileusis (LASEK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or small incision lenticule extraction (SMILE) with Plano refraction target were enrolled. Uncorrected and corrected distance visual acuity (UDVA/CDVA), manifest refraction and binocular optotype-moving DVA of 40 and 80 degrees per second (dps) were evaluated pre-operatively and post-operatively up to 3 months.

Results

The study included 264 eyes of 132 subjects, with an average age of 27.0 ± 6.7 years, and females accounted for 59% of the participants. Significant improvement was observed at the 3-month visit for 40 dps (SMILE, P = 0.001; LASEK, P = 0.006; FS-LASIK, P = 0.010) and 80 dps (SMILE, P = 0.011; LASEK, P = 0.025; FS-LASIK, P = 0.012) DVA. Adjusting for pre-operative DVA, there was no significant difference in DVA among groups at 3 months post-operatively (P > 0.05 for multiple comparisons). Overall, multiple linear models demonstrated that post-operative DVA at 3 months was correlated with pre-operative DVA (40 dps, β = 0.349, P = 0.001; 80 dps, β = 0.447, P < 0.001), pre-operative spherical equivalent (40 dps, β = 0.311, P = 0.003; 80 dps, β = 0.261, P = 0.009) and post-operative UDVA (40 dps, β = -0.224, P = 0.024; 80 dps, β = -0.188, P = 0.05).

Conclusion

Dynamic visual acuity at 3 months post-operatively of the three corneal refractive surgeries was better than that before the surgery in adult myopic patients, and there was no significant difference among different surgical techniques. Post-operative DVA at 3 months was found correlated with pre-operative DVA, pre-operative SE, and post-operative UDVA. With further improvement, DVA could be a promising functional visual indicator for myopic patients undergoing refractive surgeries.

Driving ability and predictors for driving performance in Multiple Sclerosis: A systematic review

OBJECTIVE

To provide an overview of the evidence on driving ability in persons with multiple sclerosis (PwMS), specifically to (i) study the impact of MS impairment on driving ability and (ii) evaluate predictors for driving performance in MS.

METHODS

To identify relevant studies, different electronic databases were screened in accordance with PRISMA guidelines; this includes reference lists of review articles, primary studies, and trial registers for protocols. Furthermore, experts in the field were contacted. Two reviewers independently screened titles, abstracts, and full-texts to identify relevant articles targeting driving in people with MS that investigated driving-related issues with a formal driving assessment (defined as either an on-road driving assessment; or naturalistic driving in a car equipped with video cameras to record the driving; or a driving simulator with a steering wheel, a brake pedal, and an accelerator).

RESULTS

Twenty-four publications, with 15 unique samples (n = 806 PwMS), were identified. To assess driving ability, on-road tests (14 papers) and driving simulators (10 papers) were used. All studies showed moderate to high study quality in the CASP assessment. About 6 to 38% of PwMS failed the on-road tests, showing difficulties in different areas of driving. Similarly, PwMS showed several problems in driving simulations. Cognitive and visual impairment appeared to most impact driving ability, but the evidence was insufficient and inconsistent.

CONCLUSION

There is an urgent need for more research and standardized guidelines for clinicians as one in five PwMS might not be able to drive safely. On-road tests may be the gold standard in assessing driving ability, but on-road protocols are heterogeneous and not infallible. Driving simulators assess driving ability in a standardized way, but without standardized routes and driving outcomes, comparability between studies is difficult. Different aspects, such as cognitive impairment or vision problems, impact driving ability negatively and should be taken into consideration when making decisions about recommending driving cessation.

SYSTEMATIC REVIEW REGISTRATION

Identifier [10.17605/OSF.IO/WTG9J].

Left Turns by Older Drivers With Vision Impairment: A Naturalistic Driving Study

BACKGROUND AND OBJECTIVES

Older drivers are overrepresented in collisions at intersections while making left turns across oncoming traffic. Using naturalistic driving methods, we evaluated the association between vision impairment and their left-turn characteristics.

RESEARCH DESIGN AND METHODS

In this prospective, observational study, vision impairment as defined by visual acuity, contrast sensitivity, visual processing speed, visual field sensitivity, and motion perception was assessed in drivers ≥70 years old. Data acquisition systems were installed in their personal vehicles recording video and vehicle kinematics. Driving during everyday life was recorded for 6 months. Data analysts evaluated a temporal data window surrounding randomly selected left turns at 4-way intersections. Left-turn traversals and turning behavior were evaluated in terms of age-adjusted associations with vision impairment.

RESULTS

The sample consisted of 151 older drivers. The number of turns studied was 473; 265 turns were rated as unsafe traversals, and 201 as problematic turning behavior. Drivers with slowed visual processing speed and visual field impairment were less likely to exhibit unsafe traversals (p < .05); those with worse contrast sensitivity, slowed visual processing speed, and visual field impairment were less likely to exhibit problematic turning behavior (p < .05).

DISCUSSION AND IMPLICATIONS

Using naturalistic driving, our study suggests older drivers with vision impairment exhibit better performance in making left turns than those without deficits, which contradicts older driver studies on left turns using driving simulators and on-road driving evaluations. Our findings suggest more cautious and self-regulatory behavior, which are consistent with older visually impaired drivers' commonly expressed concerns about their driving difficulties.

Hazard Perception in Older Drivers With Eye Disease

Purpose

Timely detection of hazards is a key driving skill; however, the hazard perception of drivers with eye disease and related visual changes and the visual predictors of hazard perception are poorly understood.

Methods

Participants included drivers aged 65 years and older with a range of eye diseases, including cataract, age-related maculopathy (AMD), and glaucoma (n = 99; mean age, 75.4 ± 6.4 years) and controls (n = 118; mean age, 72.2 ± 5.5 years). Visual performance was assessed using clinical measures (visual acuity, contrast sensitivity, visual fields) and non-clinical measures (useful field of view, motion sensitivity). Participants completed a computer-based hazard perception test (HPT) that has been related to driving performance and crash risk.

Results

Participants with eye disease exhibited a 0.73-second delay in HPT response times compared to controls (6.61 ± 1.62 seconds vs. 5.88 ± 1.38 seconds; age-adjusted P = 0.012). Participants with glaucoma exhibited significantly delayed responses compared to those with AMD (P = 0.038) and controls (P = 0.004). Poorer motion sensitivity (standardized β = 0.27; P < 0.001), visual acuity (β = 0.21; P = 0.002), and better-eye mean defect (β = –0.17; P = 0.009) were most strongly associated with delayed HPT responses. Motion sensitivity remained significantly associated with HPT responses, adjusted for visual acuity and visual fields.

Conclusions

HPT responses of older drivers with eye disease were delayed compared to controls and translate to an estimated 16-meter longer stopping distance when traveling at 80 km/hr. Decreased motion sensitivity was most strongly associated with delayed HPT responses.

Translational Relevance

HPT tests can provide insight into difficulties regarding road hazard detection of older drivers with eye disease and provide a potential avenue for interventions to improve road safety.

Motion perception at mesopic light levels: effects of physiological ageing and eccentricity

PURPOSE

To explore the differential effects of age and eccentricity on the perception of motion at photopic and mesopic light levels.

METHODS

Thirty-six visually normal participants (18 younger; mean age 25 years, range: 20-31) and (18 older; mean age 70 years, range: 60-79) underwent two testing sessions, one at photopic and one at mesopic light levels. In each session, motion perception was tested binocularly at two eccentricities (centrally, and peripherally at 15° rightwards and 5° superior to the horizontal) for four motion tasks: minimum contrast of a drifting Gabor to identify motion direction (motion contrast); translational global motion coherence; biological motion embedded in noise and the minimum duration of a high-contrast Gabor to determine the direction of motion, using two Gabor sizes to measure spatial surround suppression of motion.

RESULTS

There was a significant main effect of light condition (higher thresholds in mesopic) for motion contrast (p < 0.001), translational global motion (p = 0.001) and biological motion (p < 0.001); a significant main effect of age (higher thresholds in older adults) for motion contrast (p < 0.001) and biological motion (p = 0.04) and a significant main effect of eccentricity (higher thresholds peripherally) for motion contrast (p < 0.001) and biological motion (p < 0.001). Additionally, we found a significant three-way interaction between light levels, age and eccentricity for translational global motion (similar increase in mesopic thresholds centrally for both groups, but a much larger deterioration in older adult's peripheral mesopic thresholds, p = 0.02). Finally, we found a two-way interaction between light condition and eccentricity for translational global motion (higher values in central mesopic relative to peripheral photopic, p = 0.001) and for biological motion (higher values in peripheral mesopic relative to central photopic, p < 0.001).

CONCLUSIONS

For the majority of tasks assessed, motion perception was reduced in mesopic relative to photopic conditions, to a similar extent in both age groups. However, because some older adults exhibited elevated thresholds even under photopic conditions, particularly in the periphery, the ability to detect mesopic moving stimuli even at high contrast was markedly impaired in some individuals. Our results imply age-related differences in the detection of peripheral moving stimuli at night that might impact hazard avoidance and night driving ability.

With Motion Perception, Good Visual Acuity May Not Be Necessary for Driving Hazard Detection

Purpose

To investigate the roles of motion perception and visual acuity in driving hazard detection.

Methods

Detection of driving hazard was tested based on video and still-frames of real-world road scenes. In the experiment using videos, 20 normally sighted participants were tested under four conditions: with or without motion interruption by interframe mask, and with or without simulated low visual acuity (20/120 on average) by using a diffusing filter. Videos were down-sampled to 2.5 Hz, to allow the addition of motion interrupting masks between the frames to maintain video durations. In addition, single still frames extracted from the videos were shown in random order to eight normally sighted participants, who judged whether the frames were during ongoing hazards, with or without the diffuser. Sensitivity index d-prime (d′) was compared between unmasked motion (n = 20) and still frame conditions (n = 8).

Results

In the experiment using videos, there was a significant reduction in a combined performance score (taking account of reaction time and detection rate) when the motion was disrupted (P = 0.016). The diffuser did not affect the scores (P = 0.419). The score reduction was mostly due to a decrease in the detection rate (P = 0.002), not the response time (P = 0.148). The d′ of participants significantly decreased (P < 0.001) from 2.24 with unmasked videos to 0.68 with still frames. Low visual acuity also had a significant effect on the d′ (P = 0.004), but the change was relatively small, from 2.03 without to 1.56 with the diffuser.

Conclusions

Motion perception plays a more important role than visual acuity for detecting driving hazards.

Translational Relevance

Motion perception may be a relevant criterion for fitness to drive.

A sudden variation in the visual field reduces driver's accuracy in estimation of the speed of the car ahead

We offer the hypothesis that a variation in the visual environment of a driver affects their performance in estimating the speed of a car in front. The hypothesis was tested in a driving simulator with 18 drivers by recording their ability to estimate the relative speed of a car ahead when exposed to sudden variations in the visual environment. The sudden variation was produced by briefly (200 ms) masking the driving environment with a grey frame. The results of our study confirm the hypothesis, as the flashed mask significantly lowered the drivers' accuracy in estimating the speed of a car ahead. The results also show that it is possible to cope with variations in the visual environment and to partially recover from the loss of accuracy. The findings are relevant to the layout of driving environments, such as the placement of dynamic advertisements along the side of the road or the entrance zones of tunnels, and to the training of drivers. Practitioner summary: In our driving simulator study, we showed that sudden transitions in the visual environment reduce a driver's performance in evaluating the speed of the car ahead and are therefore a factor in accidents and traffic jams. Transitions should be limited, and drivers should be prepared for the effect of transitions. Abbreviation: ANOVA: analysis of variance.

Differential aging effects in motion perception tasks for central and peripheral vision

The perception of motion is considered critical for performing everyday tasks, such as locomotion and driving, and relies on different levels of visual processing. However, it is unclear whether healthy aging differentially affects motion processing at specific levels of processing, or whether performance at central and peripheral spatial eccentricities is altered to the same extent. The aim of this study was to explore the effects of aging on hierarchically different components of motion processing: the minimum displacement of dots to perceive motion (Dmin), the minimum contrast and speed to determine the direction of motion, spatial surround suppression of motion, global motion coherence (translational and radial), and biological motion. We measured motion perception in both central vision and at 15° eccentricity, comparing performance in 20 older (60-79 years) and 20 younger (19-34 years) adults. Older adults had significantly elevated thresholds, relative to younger adults, for motion contrast, speed, Dmin, and biological motion. The differences between younger and older participants were of similar magnitude in central and peripheral vision, except for surround suppression of motion, which was weaker in central vision for the older group, but stronger in the periphery. Our findings demonstrate that the effects of aging are not uniform across all motion tasks. Whereas the performance of some tasks in the periphery can be predicted from the results in central vision, the effects of age on surround suppression of motion shows markedly different characteristics between central and peripheral vision.

Scanning Behavior and Daytime Driving Performance of Older Adults With Glaucoma

PURPOSE

The purpose of this study was to assess the link between visual scanning behavior and closed-road driving performance in older drivers with glaucomatous visual impairment.

MATERIALS AND METHODS

Participants included 13 older drivers with glaucoma [mean age=71.6±7.1 y; average better-eye mean deviation (MD)=-2.9±2.1 dB, average worse-eye MD=-12.5±7.1 dB] and 10 visually normal controls (mean age=70.6±7.4 y). Visual acuity, contrast sensitivity, visual fields, useful field of view, and motion sensitivity were assessed. Participants drove around a closed-road circuit while their eye movements were recorded with an ASL Mobile Eye-XG, and head movements recorded using the gyroscope sensors of a smart phone. Measures of driving performance included hazards hit, sign recognition, and lane-crossing time; an overall driving score was derived from these component measures.

RESULTS

Participants with glaucoma had significantly poorer overall driving scores (P=0.026) and hit more hazards (P=0.043) than controls. The glaucoma group also exhibited larger saccades (P<0.001) and horizontal (P<0.001) and vertical search variances (P=0.002) than controls. Larger saccades were associated with better driving scores in the glaucoma group (P=0.001), but not the controls (P=0.75). Head movements did not differ between groups. For all participants, better-eye MD was the strongest visual predictor of overall driving score (P<0.001), followed by the other measures of visual fields, motion sensitivity, contrast sensitivity, and useful field of view (P<0.05).

CONCLUSIONS

Older drivers with glaucoma had poorer driving performance than controls and demonstrated differences in eye movement patterns. The association between larger saccades and better driving scores in those with glaucoma suggests that altering scanning behavior may benefit driving performance and safety in this group.

Visual attention to motion stimuli and its neural correlates in cannabis users

Attention to motion stimuli and correct motion perception are vital for road safety. Although cannabis use has been associated with increased road crash risks, there is limited research on attentional processing of moving stimuli in cannabis users. This study investigated the neural correlates of the three-stimulus oddball task in cannabis users (n = 18) and non-users (n = 23) in response to moving stimuli. Stimulus contrast was under 16% against a low luminance background (M luminance < 16 cd/m² ). The two groups did not differ in accuracy or in N2 peak amplitude; however, N2 latency was longer for target and standard stimuli in the cannabis group than in the control group. The cannabis group also showed a significantly reduced P3b amplitude in response to target stimuli. The AUDIT score was added as a random factor to the anova to rule out the effects of uneven alcohol consumption in the two groups. A significant group effect was found for N2 latency in response to target and standard stimuli and a significant interaction between the group, and the AUDIT score was found for the P3b peak amplitude for the distractor and standard stimuli, but not for the target stimuli. The results of this study suggest that cannabis use relates to reduced neural activity underlying attention to motion stimuli. Implications for regular early-onset cannabis use road safety are discussed.

Effect of glaucoma on eye movement patterns and laboratory-based hazard detection ability

Purpose

The mechanisms underlying the elevated crash rates of older drivers with glaucoma are poorly understood. A key driving skill is timely detection of hazards; however, the hazard detection ability of drivers with glaucoma has been largely unexplored. This study assessed the eye movement patterns and visual predictors of performance on a laboratory-based hazard detection task in older drivers with glaucoma.

Methods

Participants included 30 older drivers with glaucoma (71±7 years; average better-eye mean deviation (MD) = −3.1±3.2 dB; average worse-eye MD = −11.9±6.2 dB) and 25 age-matched controls (72±7 years). Visual acuity, contrast sensitivity, visual fields, useful field of view (UFoV; processing speeds), and motion sensitivity were assessed. Participants completed a computerised Hazard Perception Test (HPT) while their eye movements were recorded using a desk-mounted Tobii TX300 eye-tracking system. The HPT comprises a series of real-world traffic videos recorded from the driver’s perspective; participants responded to road hazards appearing in the videos, and hazard response times were determined.

Results

Participants with glaucoma exhibited an average of 0.42 seconds delay in hazard response time (p = 0.001), smaller saccades (p = 0.010), and delayed first fixation on hazards (p<0.001) compared to controls. Importantly, larger saccades were associated with faster hazard responses in the glaucoma group (p = 0.004), but not in the control group (p = 0.19). Across both groups, significant visual predictors of hazard response times included motion sensitivity, UFoV, and worse-eye MD (p<0.05).

Conclusions

Older drivers with glaucoma had delayed hazard response times compared to controls, with associated changes in eye movement patterns. The association between larger saccades and faster hazard response time in the glaucoma group may represent a compensatory behaviour to facilitate improved performance.

A brief peripheral motion contrast threshold test predicts older drivers' hazardous behaviors in simulated driving

Our research group has previously demonstrated that the peripheral motion contrast threshold (PMCT) test predicts older drivers' self-report accident risk, as well as simulated driving performance. However, the PMCT is too lengthy to be a part of a battery of tests to assess fitness to drive. Therefore, we have developed a new version of this test, which takes under two minutes to administer. We assessed the motion contrast thresholds of 24 younger drivers (19-32) and 25 older drivers (65-83) with both the PMCT-10min and the PMCT-2min test and investigated if thresholds were associated with measures of simulated driving performance. Younger participants had significantly lower motion contrast thresholds than older participants and there were no significant correlations between younger participants' thresholds and any measures of driving performance. The PMCT-10min and the PMCT-2min thresholds of older drivers' predicted simulated crash risk, as well as the minimum distance of approach to all hazards. This suggests that our tests of motion processing can help predict the risk of collision or near collision in older drivers. Thresholds were also correlated with the total lane deviation time, suggesting a deficiency in processing of peripheral flow and delayed detection of adjacent cars. The PMCT-2min is an improved version of a previously validated test, and it has the potential to help assess older drivers' fitness to drive.

Seeing pedestrians at night: effect of driver age and visual abilities

PURPOSE

To quantify the effects of driver age on night-time pedestrian conspicuity, and to determine whether individual differences in visual performance can predict drivers' ability to recognise pedestrians at night.

METHODS

Participants were 32 visually normal drivers (20 younger: M = 24.4 years ± 6.4 years; 12 older: M = 72.0 years ± 5.0 years). Visual performance was measured in a laboratory-based testing session including visual acuity, contrast sensitivity, motion sensitivity and the useful field of view. Night-time pedestrian recognition distances were recorded while participants drove an instrumented vehicle along a closed road course at night; to increase the workload of drivers, auditory and visual distracter tasks were presented for some of the laps. Pedestrians walked in place, sideways to the oncoming vehicles, and wore either a standard high visibility reflective vest or reflective tape positioned on the movable joints (biological motion).

RESULTS

Driver age and pedestrian clothing significantly (p < 0.05) affected the distance at which the drivers first responded to the pedestrians. Older drivers recognised pedestrians at approximately half the distance of the younger drivers and pedestrians were recognised more often and at longer distances when they wore a biological motion reflective clothing configuration than when they wore a reflective vest. Motion sensitivity was an independent predictor of pedestrian recognition distance, even when controlling for driver age.

CONCLUSIONS

The night-time pedestrian recognition capacity of older drivers was significantly worse than that of younger drivers. The distance at which drivers first recognised pedestrians at night was best predicted by a test of motion sensitivity.

Age-related changes in perception of movement in driving scenes

PURPOSE

Age-related changes in motion sensitivity have been found to relate to reductions in various indices of driving performance and safety. The aim of this study was to investigate the basis of this relationship in terms of determining which aspects of motion perception are most relevant to driving.

METHODS

Participants included 61 regular drivers (age range 22-87 years). Visual performance was measured binocularly. Measures included visual acuity, contrast sensitivity and motion sensitivity assessed using four different approaches: (1) threshold minimum drift rate for a drifting Gabor patch, (2) Dmin from a random dot display, (3) threshold coherence from a random dot display, and (4) threshold drift rate for a second-order (contrast modulated) sinusoidal grating. Participants then completed the Hazard Perception Test (HPT) in which they were required to identify moving hazards in videos of real driving scenes, and also a Direction of Heading task (DOH) in which they identified deviations from normal lane keeping in brief videos of driving filmed from the interior of a vehicle.

RESULTS

In bivariate correlation analyses, all motion sensitivity measures significantly declined with age. Motion coherence thresholds, and minimum drift rate threshold for the first-order stimulus (Gabor patch) both significantly predicted HPT performance even after controlling for age, visual acuity and contrast sensitivity. Bootstrap mediation analysis showed that individual differences in DOH accuracy partly explained these relationships, where those individuals with poorer motion sensitivity on the coherence and Gabor tests showed decreased ability to perceive deviations in motion in the driving videos, which related in turn to their ability to detect the moving hazards.

CONCLUSIONS

The ability to detect subtle movements in the driving environment (as determined by the DOH task) may be an important contributor to effective hazard perception, and is associated with age, and an individuals' performance on tests of motion sensitivity. The locus of the processing deficits appears to lie in first-order, rather than second-order motion pathways.