A new study from the University of Washington (UW) and the Toyota Research Institute (TRI) has found that the increasingly common touchscreen interfaces in modern cars significantly impair both driving performance and touchscreen accuracy especially when drivers are under additional cognitive strain. The findings arrive as automakers replace physical knobs and buttons with large digital displays, raising questions about safety and human attention.

　　Driving performance drops as touchscreen use and mental load rise

Researchers placed 16 participants in a vehicle simulator equipped with a 12-inch center touchscreen, tracking eye movements, finger movements, pupil dilation, and electrodermal activity to measure cognitive load. Drivers were asked to interact with on-screen targets while simultaneously performing an N-back memory task that mimics the mental effort of navigating traffic, hearing alerts, or processing roadside information.

Across the board, multitasking pushed both driving and touchscreen performance in the wrong direction. When drivers used the touchscreen, they drifted within their lane 42% more frequently, even before additional cognitive tasks were introduced. Touchscreen performance also dropped sharply: accuracy and speed fell 58% while driving, and a further 17% under high mental load.

Recommended Videos Attention management also deteriorated. Under greater cognitive load, each glance at the touchscreen became 26% shorter, suggesting rushed or fragmented visual checks. Meanwhile, drivers increasingly reached for the screen before looking at it the hand-before-eye pattern rising from 63% to 71% during memory tasks which likely contributed to missed taps and longer visual searches.

　　Perhaps most surprisingly, making the on-screen touch targets bigger didnt help.

The thing that takes time is the visual search, explained lead author Xiyuan Alan Shen. Drivers hands often move before their eyes, so bigger buttons dont fix the core issue.

The results highlight a growing tension in automotive design: touchscreens offer flexibility, customization, and sleek aesthetics, but they also demand more of a drivers eyes and mind than tactile controls ever did. As dashboards increasingly resemble tablets, the question becomes how much interaction is safe at highway speeds.

The team presented the findings September 30 at the ACM Symposium on User Interface Software and Technology in Busan, Korea, noting that the work provides a foundation for safer in-car interface design as touchscreens become standard across the industry.