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Eye movement and driving behaviour in curved section passages of an urban motorway

Eye movement and driving behaviour in curved section passages of an urban motorway. I Hong, M Iwasaki, T Furuichi, and T Kadoma Proc. IMechE Vol. 220 Part D: J. Automobile Engineering. Introduction. Quantitative indicators of actions related to vehicle control while driving include: Speed

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Eye movement and driving behaviour in curved section passages of an urban motorway

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  1. Eye movement and driving behaviour in curved section passages of an urban motorway I Hong, M Iwasaki, T Furuichi, and T Kadoma Proc. IMechE Vol. 220 Part D: J. Automobile Engineering

  2. Introduction • Quantitative indicators of actions related to vehicle control while driving include: • Speed • Acceleration • Braking • Steering angle • Then drivers have taken in various kinds of information with their sensory organs and processed that information. During this process, perception errors sometimes occur.

  3. Introduction • The curved sections passages of urbanmotorway is fairly severe The driver’s workload is high, making it easy for human errors to occur • The study focuses on single-car collisions occurring primarily in free-flow regions. • Using the results of the experiment • Analysis the factors that produce human error in relation to motorway alignment. • Eye movement, and centrifugal acceleration in the curved sections

  4. LITERATURE REVIEW • Vision is the main sense for taking in information while driving • over 90 per cent of the information obtained while driving is taken in visually. [1] • That 50 per cent of accidents involve perceptual factors and 16.2 per cent of these correspond to a lack of visibility. • This lack is probably causes of the higher concentration of accidents at corners in urban zones. [3] • An experiment on a rural road with varying accidentfrequencies • eye fixation times on curved sections ofroads with a large number of accidents tend to belonger than smaller number of accidents. [4]

  5. LITERATURE REVIEW • Vision is the main sense for taking in information while driving • experiment on sloping sections of road at points high and low incidences of accidents • By looking at a driver’s saccadic distance and eye fixation time that lower on curved sections with high incidences of accidents [5] • driver’s depth and breadth of apprehension are not compatible, but rather that there is a trade-off between the two [6]

  6. LITERATURE REVIEW • All of the above studies were based on an in-car experiment but barely give any consideration to an approach that • grasps the driver the vehicle • road as a single system • relationship between eye fixation behaviour and vehicle control • one of the factors that takes human error into consideration.

  7. LITERATURE REVIEW • Studies on vehicle movement in curved sections • The studies focus primarily on the driver–vehiclerelationship, theorizing about general trends in driverbehaviour. • Concrete descriptions of the roadwaysections are lacking. • There are few comparisonsof driver behaviour on sections with high and lowincidences of accidents.

  8. LITERATURE REVIEW • Studies on vehicle movement in curved sections • workload while driving on curved sections canbe measured through experiments with altered curveradii and speeds[8] • there is a limit value for how much centrifugalacceleration a driver can sustain while driving on curved sections, and that this value varies dependingon the driver’s situation[9] • Errorsin judgement by drivers regarding curvature whendriving through curved sections are compensated forbased on feedback from centrifugal acceleration.[10]

  9. IN-CAR EXPERIMENT • Sites and subjects • A number of S-shaped curved sections of the Tokyo Metropolitan Expressway • Accident statistics rates were estimated for each curved section. • First (entry) curve of the S-shape • Second (exit) curve of the S-shape • The S-shaped curved sections are characterized by repeated curving, so as long as there are no on-ramps or off-ramps, traffic conditions can be considered to be equivalent throughout.

  10. IN-CAR EXPERIMENT • Example of a simplified representation of the horizontal alignment of the two S-shaped curves used in the experiment. • Arrows the direction that was analysis in this study • The S-shaped curves indicated contain distances (km) marked for direction(North etc.) used in the experiment • parentheses are the accidents rates (numberof accidents per 100 million vehicle-km)

  11. IN-CAR EXPERIMENT • Sites and subjects • The traffic volume was relatively light and traffic conditions were such that the drivers were able to drive unencumbered. • Eight drivers were allmales in twenties and experiment used for each route. • For reduce danger the experiments were not conducted at night.

  12. IN-CAR EXPERIMENT • Sites and subjects • Each driver completed two round trips on the targetsections • first time through, driving was in theshoulder lane • second time, it was in the medianlane • Drivers were instructed to drive as close to their normal driving behaviour as possible. • An eye mark recorder was used to measure driver eye movement

  13. IN-CAR EXPERIMENT • Measuring devices and data collection • A minivan equipped with measuring devices. • Speed • steering angle • pressure on the accelerator • travelling position were measured as digital data

  14. IN-CAR EXPERIMENT • Measuring devices and data collection • EMR-8B was used to measure eye movement • the horizontal direction of an eyeball • the perpendicular amount of rotations • Eye fixation times and number of eye fixations for each driver were processed with NAC EMR-8B analysis software. • It was not possible to obtain valid data for every driver that participated in the study.

  15. IN-CAR EXPERIMENT • Data derivation — Calculation for centrifugal acceleration • Centrifugal acceleration is a quantity determined by the speed and steering angle of a vehicle travelling through a curved section. • By the Japan Highway Geometry Design Code, the rate is used as one of the design indices at the curve section. • Actual vehicle speeds, however, are not the design speeds and the vehicle trajectory is not the same as the alignment.

  16. IN-CAR EXPERIMENT • Data derivation — Calculation for centrifugal acceleration • The centrifugal acceleration(α)was calculated using the following formula • Φmax =t urn of the front wheels at the maximum steering angle (deg) • h = steering angle (deg) • hmax= maximum steering angle (deg)

  17. IN-CAR EXPERIMENT • Data derivation — Mean eye fixation time and mean number of eye fixations • The eye movements of drivers related to visually gathering information include saccadic movement and pursuit movement. • During the saccade movement, no information is passed through the optic nerve to the brain. • As a general rule, saccades last from about 20 to 200 ms. • Pursuit movement is the ability of the eyes to follow a moving object around.

  18. IN-CAR EXPERIMENT • Data derivation — Mean eye fixation time and mean number of eye fixations • In this study, the eye fixation time is defined as continuously looking at the same thing for more than 0.165 s [13] Ta = mean eye fixation time (s) Na = mean number of eye fixations (1/s) T1 = time required to pass through the curve (s) Tt = total eye fixation time in the section (s) Nt = total number of eye fixations in the section

  19. IN-CAR EXPERIMENT • Data derivation — Horizontal eye movement • Horizontal visual angle is defined as the angle to the eye fixation position based on the direction the vehicle is moving • It was presupposed that every 10 metres the car moved parallel to the centre-line of the lane. • Using the horizontal alignment diagram, the angle formed by the eye fixation point, which was photographed every 10 metres by the eye mark recorder.

  20. IN-CAR EXPERIMENT • Running behaviour in curved sections • Speed and centrifugal acceleration in curved sections • The figure shows the results from route 3, westbound and route 2, southbound. speed Steering angle centrifugal acceleration Vertical and horizontal alignment

  21. IN-CAR EXPERIMENT • Running behaviour in curved sections • On route 2 • There was hardly any deceleration in the S-shaped curved sections. • that the drivers judged that they were able to pass through the S-curves at the same speed as that when they entered.

  22. IN-CAR EXPERIMENT • Running behaviour in curved sections • Route 3 • Each driver passed through the S-shaped sections by decelerating before entering the second curve. • There were hardly any differences therefore in centrifugal acceleration on the two curves. • The steering angle while passing through the curved sections was constantly changing. • The steering wheel operation indicates that the workload of the drivers was quite high.

  23. IN-CAR EXPERIMENT • Running behaviour in curved sections • qualitatively summarizes the average characteristics of the drivers Arrows: the speed column indicate acceleration or deceleration Stable/unstable: the steering wheel whether or not steering corrections were made High/low: the magnitude of centrifugal acceleration occurring in a section

  24. Relationship between the mean eye fixation time and the mean number of eye fixations • When driving on curved sections of the same distance at the same speed, if the time of each eye fixation is long, then the number of eye fixations decreases. Relationship between fixation and fixation duration

  25. Relationship between the mean eye fixation time and the mean number of eye fixations • Formulating the trade-off relationship, the avalue shows the trade-off relation between the mean eye fixation time and the number of eye fixations. Ta=mean eye fixation time (s/fixation) Na=number of eye fixations (number of times/s) a = Ta Na

  26. Relationship between the mean eye fixation time and the mean number of eye fixations • Figures show the results of the real relationship between the mean eye fixation time and the mean number of eye fixations

  27. Relationship between the mean eye fixation time and the mean number of eye fixations • Table shows values of each curve as inferred from the data obtained in the experiment Estimated accidents rate

  28. Relationship between the mean eye fixation time and the mean number of eye fixations • Table shows values of each curve as inferred from the data obtained in the experiment Estimated accidents rate

  29. Relationship between the mean eye fixation time and the mean number of eye fixations • Comparing the relationship between estimated accident rates and the avalue of the first and second curves • it is found that in 9 out of a total of 14, ais large for sections where the estimated accident rate is high. • By extension,this would mean that the amount of informationdrivers take in visually increases in sections with highestimated accident rates. • Consequently, in curvedsections with high accident rates, drivers drive whileeither frequently moving their eyes or focusing on asmall number of eye fixation points.

  30. Relationship between the mean eye fixation time and the mean number of eye fixations • In fact, when there is a difference in the estimated accident rates between the first and second curves of an S-curve, the value of atends to be larger in the section where the accident rate is high. • means in curves with high estimated accident rates, extraneous information that diverts the driver’s attention is mixed in with the information taken in by the driver.

  31. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Threshold value of centrifugal acceleration • Centrifugal acceleration is used as an indicator to judge the driving state. • based on the supposition that exceeding a fixed threshold for centrifugal acceleration is a latent condition for human error. • this supposition, driving behaviour that exceeds the centrifugal acceleration threshold on curved sections will be discussed and analysed. • centrifugal acceleration threshold at or above the average +1.64δ was used, which means that a 5 per cent or less probability of the centrifugal acceleration threshold value being generated was applied.

  32. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • As a driver drives, there is a time delay between perception and reaction. • the eye fixation behaviour and driving of drivers will be looked at from the point centrifugal acceleration exceeds the threshold ‘section under review’) to a point a distance upstream (‘immediate upstream section’) • for the two sections the driver eye fixation targets and the change in the average rate of movement in horizontal eye fixation points will be analysed.

  33. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • The average rates of movement in horizontal eye fixation points in the immediate upstream sections and the sections under review.

  34. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • typical horizontal eye fixation angles seen in some sections

  35. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • With images from the eye mark recorder

  36. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • Case A: before entering the curved section and nearthe end of the section • Case B: before entering the curved section • Case C: while driving through the curved section • Case D: near the end of the curved section • In Cases A, B, and D, horizontal eye movementinthe immediate upstream section was relativelyfrequent.

  37. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • Conversely, there were many drivers whoserange of eye fixation on this road section was narrowand whose rate of movement in horizontal eyefixation points was slow compared to the immediateupstream section. • This kind of eye behaviour in thesection under review can be explained by the drivertrying to stabilize the driving position of vehicle.

  38. EYE MOVEMENT OF DRIVERS WHO EXCEED THE THRESHOLD • Eye movement characteristics in curvedsections • In Case C, horizontaleye movement was frequent in the section underreview even though centrifugal acceleration waselevated. It can be hypothesized that : • The driver’sworkload was high compared to the other cases • at the same the driver was making corrections withthe steering wheel while driving through the sectionunder review • Meaning that there was instability inthe driving of the vehicle.

  39. RELATIONSHIP BETWEEN DRIVER EYEMOVEMENT AND ROADWAY ALIGNMENT INCURVED SECTIONS • The relationship betweenthe model constructed, TaNa=a, for the mean eyefixation time and the mean number of eye fixations,and roadway alignment and estimated accident ratesfor curved sections. • (a) shows that a or a variation of a increases with a lower curve radius. • means that the curve radius becomes large and a cognitive workload increases.

  40. RELATIONSHIP BETWEEN DRIVER EYEMOVEMENT AND ROADWAY ALIGNMENT INCURVED SECTIONS • And found that ais dependent on the radius of each curve and that it tends to have a fixed upper limit (b) • Based on the relationships shown in (a) and (b) • the fact that the amount of information that must be taken in by the driver in a curved section increases means that the section has a high likelihood of accidents occurring.

  41. RELATIONSHIP BETWEEN DRIVER EYEMOVEMENT AND ROADWAY ALIGNMENT INCURVED SECTIONS • Given the relationship discussed above between a curve’s radius and a • determined by the estimated accident rate and the driver’s eye fixation behaviour, it can be concluded that the avalue • related to eye fixation behaviour, can be used as one of the indicators for evaluating the relationship between driver behaviour in a curved section and the roadway alignment.

  42. Result • There were some drivers who operated a constantly changing steering angle while passing through the curved sections where there was a high accident rate. • Such steering operation indicates that the workload of the drivers was quite high. • The trade-off relationship between the mean eye fixation time and the mean number of eye fixations can be formulated as TaNa=a.

  43. Result • Centrifugal acceleration was a useful indicator to analyse driving attitude and eye movement of a driver passing through curved sections. • The a value, which is related to eye fixation behaviour, can be used as one of the indicators • for evaluating the relationship between driver behaviour in a curved section and the roadway alignment. • The curved section where ais high has a tendency for unstable steering operation.

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