A recent Rutgers University study found that one in six young drivers — ranging in age from 18 to 25 — reported they had used their phones behind the wheel while feeling sleepy.

The research project, which relied on responses from 110 undergraduate commuters, also found that 80% of those surveyed said they used a cell phone with the speaker on while driving. About two-thirds of respondents admitted they still held the phone with one hand using the speaker mode while driving.

Drivers 25 and under are particularly at risk for such behavior because they’re more likely to report having fallen asleep behind the wheel and more likely to text while driving than any other age group.

The next step in the study is to take a deeper look at the data to see how many drivers reported engaging in multiple risky behaviors simultaneously.

Derek Shendell, an associate professor at Rutgers School of Public Health, supervised the study. Amber Gourdine and Sonia Lee, who have since graduated, conducted the research.