With its large aging population and a transportation system centered on cars, the United States is home to a growing number of older drivers. In 2020, there were almost 48 million licensed drivers aged 65 and older in the U.S. However, age-related declines in cognitive, visual, and physical functions pose potential challenges for older drivers, raising concerns about safety.

A recent study by University of Iowa researchers looked at the relationships between older drivers’ driving errors and two important crash risk factors: vehicle actions (such as making turns, changing lanes, and merging) and traffic control devices (such as traffic signals, stop signs, and yield signs). The study was published in the Feb. 2025 issue of the Journal of Safety Research.

The study used crash data from the Iowa Department of Transportation from 2010 to 2020. The study sample included 254,912 drivers aged 45 or older who were involved in a crash. Drivers aged between 45 and 64 formed the comparison group, and drivers aged 65 and older were divided into three older driver groups (ages 65–74, 75–84, and 85+). Driving errors were identified based on driver contributing factors reported in the Iowa crash data.

Key findings of the study included:

• Driving errors contributing to crashes increased with age, especially in the 75–84 age group.
• Older drivers may face age-related challenges in performing specific driving behaviors with age, such as turning and changing lanes.
• These challenges can differ across age groups within older adults.
• Studies on older drivers should avoid treating older adults as a uniform group and instead examine differences among age groups.

“We found that drivers in the 75-84 age group were more likely to be culpable in right turn-related crashes compared to younger age groups, which may be related to reduced physical flexibility or visual declines,” said Gilsu Pae, a postdoctoral scholar in the University of Iowa (UI) Department of Epidemiology and first author of the study. “Drivers 75-84 were also more likely to be culpable in crashes at locations with traffic signals, which may also be due to visual declines or decreases in reaction times compared to younger age groups.”

The researchers also noted that because older adults are often expected to continue driving later in life than previous generations, safety policies should be customized to the different aging phases of older adults.

“Some driving-related burdens are likely to become excessive at and after the middle-old age (75–84),” the researchers wrote. “Therefore, careful evaluations of older drivers’ ability to drive safely are needed once drivers reach this age group, particularly during the driver’s license renewal process, without unintentionally implying an immediate cessation of driving.”

The authors also stressed the need to develop advanced technologies, traffic systems, and policies to reduce the driving burdens associated with aging.

In addition to Pae, the research team also included Jonathan Davis and Cara Hamann, UI Department of Epidemiology; Joe Cavanaugh, UI Department of Biostatistics; and Motao Zhu, The Ohio State University.