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 impact both driving performance and touchscreen accuracy – especially when drivers are placed under additional cognitive load. The findings come at a time when automakers are replacing physical buttons and buttons with large digital displays, raising questions about safety and human attention.
Driving performance decreases as touchscreen use and mental load increase
Researchers placed 16 participants in a vehicle simulator equipped with a 12-inch center touchscreen that tracked eye movements, finger movements, pupil dilation and electrodermal activity to measure cognitive load. Drivers were asked to interact with targets on the screen while simultaneously performing an “n-back” memory task that mimics the mental effort of navigating traffic, hearing warnings or processing road information.
Overall, multitasking skewed both driving and touchscreen performance in the wrong direction. When drivers used the touchscreen, they were 42% more likely to drift within their lane, even before additional cognitive tasks were introduced. The performance of the touchscreen also fell sharply: accuracy and speed fell by 58% when driving, and by a further 17% during high mental stress.
Attention management also deteriorated. When cognitive load was higher, each glance at the touchscreen became 26% shorter, suggesting rushed or fragmented visual controls. Meanwhile, drivers increasingly reached for the screen before looking at it – the hand-over-eye pattern increased from 63% to 71% in memory tasks – likely contributing to missed taps and longer visual searches.
Perhaps most surprisingly, increasing the size of the touch targets on the screen didn’t help.
“What takes time is visual search,” explained lead author Xiyuan Alan Shen. “Drivers’ hands often move in front of their eyes, so larger buttons don’t solve the core problem.”
The results illustrate a growing tension in automotive design: touchscreens offer flexibility, customization and elegant aesthetics, but also demand more of the driver’s eyes and mind than tactile controls ever did. As dashboards increasingly resemble tablets, the question arises as to how safe the interaction is at highway speeds.
Researchers say future systems may need integrated intelligence. Eye-tracking or steering wheel sensors could detect when a driver is overloaded and automatically adjust the interface – enlarging key controls, simplifying menus or suppressing unnecessary prompts until attention is available again.
The team presented the findings Sept. 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.
