University of California Institute of Transportation Studies

Drivers know that smartphones distract. Trying to limit distraction, drivers can use handsfree devices, where they onlybriefly glance at the smartphone. However, the cognitive cost of switching tasks from driving to communicating back todriving adds an underappreciated, potentially long period to the total distraction time. This project measured the effectsof handsfree smartphones on driving behaviors by engaging ninety-seven 21- to 78-year-old individuals whoselfidentified as active drivers and smartphone users in a simulated driving scenario that included smartphonedistractions. Peripheral-cue and car-following tasks were used to assess driving behavior, along with synchronized eyetracking. This research found that simulated driving performance drops to dangerous levels after smartphone distractionfor all ages and for both voice and texting. The participants swerved for 15.1 seconds after a voice distraction and for alonger 20.6 seconds after a text distraction. Participants from the 71+ age group missed seeing about 50% of peripheralcues within 4 seconds of the distraction. Coherence with the lead car during following task dropped from 0.54 to 0.045during distraction, and seven participants rear-ended the lead car.