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Steven Savage, Lily Zhang, Garrett Swan, Alex R Bowers; How does age affect the contributions of head and eye movements to scanning at intersections?. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3912. doi: https://doi.org/.
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Older drivers are more likely to be involved in collisions at intersections. One reason may be that they do not visually scan their surroundings sufficiently well to detect hazards in a timely manner. Prior studies are conflicting and mostly based on head tracking (some reported older drivers made smaller and fewer scans than younger drivers, while others found no age differences). A more detailed investigation of head and eye movement scanning is needed, however, because older drivers may, for instance, make more use of eye than head movements as a result of reduced neck flexibility. We, therefore, evaluated the effects of age on the contributions of both head and eye movements to scanning at intersections.
Eleven older (mean 67 years, range 61-81) and 18 younger (mean 27 years, range 20-41) current drivers with normal vision, drove in our simulator while their eye and head movements were tracked using a six-camera remote system. They completed 2 drives in a city, each about 15 minutes with 42 intersections. Scans, analyzed for 15 four-way intersections without cross traffic, were split into two categories: eye-only (consisting only of eye movements) and eye+head (a lateral head rotation with one or more eye saccades superimposed).
Older drivers made significantly more eye-only scans than younger drivers (7.2 vs. 6.0 per intersection; p=.03) but fewer eye+head scans (2.1 vs. 2.8: p=.01), resulting in no age effects for all scans (p = .19). Older drivers made substantially smaller eye+head scans than younger drivers (35.5° vs. 47.3°, p<.001) as well as smaller eye-only scans (11° vs 12.3°, p= .02). For eye+head scans, older drivers made both a smaller head movement (19.8°, vs. 24.6°; p=.006) and had a smaller eye movement component (15.5° vs. 22.7°; p<.001).
Tracking both head and eye movements and splitting scans into two categories, provides new insights into scanning behaviors on approach to intersections. Older subjects made fewer of the large eye+head scans but more of the smaller eye-only scans. For eye+head scans, older subjects made both a smaller head movement and had a smaller eye movement component. These results may have important implications for driving safety as preliminary analyses of data from intersections with cross traffic suggest that more scans and larger scans are associated with safe detection of motorcycle hazards.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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