The Effects of Age, Distraction, and Simulated Central Vision Impairment on Hazard Detection in a Driving Simulator

Abstract

Significance: Despite similar levels of visual acuity and contrast sensitivity reductions, simulated central vision impairment increased response times to a much greater extent in older than in younger participants.

Purpose: Driving is crucial for maintaining independence in older age, but age-related vision impairments and in-vehicle auditory distractions may impair driving safety. We investigated the effects of age, simulated central vision impairment, and auditory distraction on detection of pedestrian hazards.

Methods: Thirty-two normally sighted participants (16 younger and 16 older) completed four highway drives in a simulator and pressed the horn whenever they saw a pedestrian. Pedestrians ran toward the road on a collision course with the approaching vehicle. Simulated central vision impairment was achieved by attaching diffusing filters to a pair of laboratory goggles, which reduced visual acuity to 20/80 and contrast sensitivity by 0.35 log units. For drives with distraction, subjects listened to an audiobook and repeated out loud target words.

Results: Simulated central vision impairment had a greater effect on reaction times (660-millisecond increase) than age (350-millisecond increase) and distraction (160-millisecond increase) and had a greater effect on older than younger subjects (828- and 492-millisecond increase, respectively). Simulated central vision impairment decreased safe response rates from 94.7 to 78.3%. Distraction did not, however, affect safety because older subjects drove more slowly when distracted (but did not drive more slowly with vision impairment), suggesting that they might have perceived greater threat from the auditory distraction than the vision impairment.

Conclusions: Older participants drove more slowly in response to auditory distraction. However, neither older nor younger participants adapted their speed in response to simulated vision impairment, resulting in unsafe detections. These results underline the importance of evaluating safety of responses to hazards as well as reaction times in a paradigm that flexibly allows participants to modify their driving behaviors.

Figure 1.

LE-1500 driving simulator (FAAC, Inc., Ann Arbor, MI) used in this study. The auditory distraction task was delivered though a pair of speakers (Amazon Basics A100 Multimedia Speakers, China) positioned to the left and right of the participant’s seat (white circle). A video recorder (yellow circle – DVC, WEILIANTE Co., Ltd, China) was positioned above and behind the car seat to simultaneously record participants’ repetition of target words in the auditory distraction task along with video of the central screens of the simulator (to facilitate scoring of auditory task performance for segments without and with pedestrians on the screen).

Figure 2.

Average reaction time for each condition plotted separately for older and younger subjects. Error bars represent the standard error of the mean (SEM).

Figure 3.

Percent of safe detections for each condition split by older and younger subjects. Error bars represent the standard error of the mean (SEM).

Figure 4.

Boxplots for vehicle speed of older and younger subjects for each condition. Thick black line represents group median; box extent represents the inter quartile range (IQR); plot whiskers represent 1.5x IQR; and filled circles represent outliers beyond 1.5x IQR. (Note: the y-axis has been truncated and runs from 40–100 km/h)

Figure 5.

Boxplots of average percentage of words recalled both during pedestrian events (left) and between pedestrian events (right) plotted separately for older and younger subjects. Thick black line represents group median; box extent represents the inter quartile range (IQR); and plot whiskers represent 1.5x IQR.