Assisting the older driver - SWOV

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Effects of intersection design on workload and driving performance Workload was measured by performance on a secondary task while passing the intersection. The secondary task consisted of a peripheral detection task (PDT; see e.g., Van Winsum, Martens & Herland, 1999 for a description of this task). While driving, a small red square was presented on the simulator screen in front of the participant during one second. Subjects were required to respond as soon as they detected the red square by pressing a microswitch that was attached to the index finger of their left hand. Reaction time was measured in milliseconds. If a reaction time had not been detected by the system within 2.5 s from the onset of the stimulus, this was coded as a missed signal. Series of signals were presented during the approach and passing of a selected number of intersections and while driving on three straight road sections. The 28 selected intersections were representative for the total group of 71 intersections, at the same time preventing participants having to perform the detection task at every intersection they passed. The onset of a series of signals was announced with a bell tone. During the series of signals (one series per intersection), on average every 3.5 s, with random variation between 3 and 4 s, a stimulus was presented at a horizontal angle of 10 to 20 degrees to the left of the line between the eyes of the participant and the centre of the screen. Stimuli were presented at a vertical angle of 3 degrees above the horizon. Average reaction time and fraction of missed signals per intersection (number of missed signals divided by total number of sent signals while passing the relevant intersection) were used as workload indices for the intersections. Higher reaction times and higher fractions of missed signals were interpreted as being the result of a higher workload. Baseline reaction times and fractions missed were collected at the start of the first experimental drive. While the simulator car was parked at the beginning of the route, and the participant was sitting in the driver seat, one series of twenty stimuli was presented. On average every 4 s, with random variation between 3 and 5 s, a stimulus was presented at a horizontal angle of 10 to 20 degrees to the left of the line between the eyes of the participant and the centre of the screen. Again, participants were instructed to press the button as soon as they saw the stimulus. A second baseline was provided by the straight road sections at which the same series of stimuli were shown as during the approach and passing of the selected number of intersections. This second baseline differed from the first one in three ways: 1) participants were driving, 2) it always took place during the same drive as in which the relevant intersection data were gathered (no support), whereas the first baseline also could have taken place at the start of the drive in which driver 113
Assisting the older driver support was available, and 3) the frequency at which the stimuli were presented was every 3.5 s instead of every 4 s. Practise on the PDT was provided during the familiarization run. 6.3. Results In this section, between‐subjects comparisons focus on functional age. Within‐subjects comparisons focus on the effects of different types of intersections and manoeuvres. 6.3.1. General driving performance Waiting position before passing an intersection, and acceleration and speed while passing an intersection were averaged per required driver manoeuvre: crossing a street while driving straight ahead, joining traffic after turning left or right, or turning left in front of an approaching vehicle. Age groups only differed in their waiting position before entering the intersection. Functionally old participants generally stopped two meters further away from the intersection to decide whether it was safe to join traffic after turning left or right than both young and middle‐aged participants did (t(18) = ‐ 3.188, p = 0.005 and t(28) = ‐ 2.739, p = 0.011 respectively). In addition, while stopping in front of the intersection before crossing it, functionally old participants had a lateral position that was closer to the side of the road than both young and middle‐aged participants had (t(11) = 2.405, p = 0.036 and t(12) = 2.840, p = 0.015 respectively). Acceleration and speed while passing intersections did not differ between age groups. 6.3.2. Workload Before any of the analyses with regard to workload were carried out, all average reaction times – those averaged per intersection as well as those averaged per baseline – were first corrected for missing data. Initially, average reaction times represented the average of the reaction times for those stimuli to which participants had reacted within 2.5 s. If a participant had not reacted within 2.5 s after the onset of a stimulus, the reaction time for that stimulus was coded as missing, and the corresponding average reaction time per intersection or baseline was based on a lower number of stimuli. A reason for not having reacted within 2.5 s could either be not having noticed the stimulus or not having reacted quickly enough. In both cases, no attentional capacity was left to notice and or react to the stimulus in time. Had the stimulus been presented for a longer span of time, or had we waited 114
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SWOV‐Dissertatiereeks, Leidschend
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Assisting the older driver Appendix
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Samenvatting Samenvatting Dit proef
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Samenvatting Verkeersveiligheidsmaa
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Samenvatting jongere automobilisten
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Samenvatting voordeel dat ze de rij
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Curriculum Vitae Curriculum Vitae R
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Assisting the older driver Nottingh
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