The Relationship Between Visual Abilities and Driving Habits Among Older Drivers: A LongROAD Study
This research brief assesses driving habits related to visual function using objective measures of driving amongst older driver participants in the LongROAD study.
October 2018
Suggested Citation
For media inquiries, contact:
Tamra Johnson
202-942-2079
TRJohnson@national.aaa.com
Abstract
This study examines the relationship between measures of visual function at baseline and objective measure of driving habits averaged over a one-year follow-up period in a sample of older drivers. Results showed that participants had relatively good visual function at the time of their enrollment in the study. Analyses found that lower visual acuity and visual-spatial abilities were related to the driving behavior categories of staying closer to home, less driving overall and greater driving avoidance, although not for every measure. Poorer contrast sensitivity, which is related to one’s ability to see in low-light conditions, was associated with avoidance of both nighttime driving and driving on high-speed roads but was not related to driving closer to home or overall driving.
Key Findings
- Lower visual acuity and visual-spatial abilities were related to the driving behavior categories of staying closer to home, less driving overall and greater driving avoidance, although not for every measure
- Poorer contrast sensitivity was associated with avoidance of nighttime driving and driving on high-speed roads but was not related to measures of driving closer to home or exposure
The driving habit measures used in this study included two measures of driving closer to home (percentage of trips within 15 miles of home and percentage of trips within 25 miles of home), driving exposure (average miles driven per month and average days driven per month) and driving avoidance (average percentage of trips at night and average percentage of trips on high-speed roads). Definitions of these measures are shown in the table below.
Methodology
Study data were obtained from measurements of visual function and objective driving data averaged over 12 months following baseline assessment of active drivers ages 65-79 enrolled in the LongROAD multisite prospective cohort study. The driving data were filtered to identify participants with at least 12 full months of data at the time of analysis (n=2,131) and the remaining participants were excluded. For participants with more than one year of data, only the first 12 months were analyzed. The objective driving habit measures were based on previous work and were conceptualized based on three components of the Driving Habits Questionnaire: driving closer to home (called driving space), driving exposure and driving avoidance. The objective driving habit measures used were similar to the self-reported topics addressed in the DHQ but derived from data recorded from a small GPS device installed in each participant’s vehicle. This system automatically recorded all driving when the vehicle was turned on and could determine whether or not it was the participant who was driving.
Results
The study found that both measures of driving close to home were significantly associated with visual acuity and visual-spatial scores, with scores indicating poorer visual function being associated with a higher percentage of trips close to home. Contrast sensitivity was not associated with measures of driving close to home. Analysis of the two driving exposure measures showed that average miles driven per month were significantly lower in the group with impaired acuity. Contrast sensitivity and visual-spatial scores were not statistically associated with this measure but lower visual-spatial scores were associated with a greater average number of days driving per month. To explore this finding further, we divided the average monthly days of driving scores into quartiles and determined the average visual-spatial score for each quartile. We found no evident trend that explains the significant but very small correlation. Both driving avoidance measures were associated with all three visual function measures, except that percentage of trips on high-speed roads was not associated with visual acuity. In all significant cases, better visual function scores were associated with increasing average percentages of trips at night and on high-speed roads.
Suggested Citation
For media inquiries, contact:
Tamra Johnson
202-942-2079
TRJohnson@national.aaa.com