Most drivers like to think they are in full control of their driving, even when they are feeling sleepy. But hasn’t every driver at some time woken up to find they are wandering off the road, or worse?

We have long known that the eyes are a pretty good indicator of falling asleep. Research by Filtness et al. (2014) had 16 drivers undertake drives on real roads and on a driving simulator both during the daytime and at night. At the end of each drive, ten eye symptoms were rated and compared with subjective measures of performance and actual objective driving performance measures.

The four key eye measures rated as symptoms of sleepiness were: ‘eye strain’, ‘heavy eyelids’, ‘difficulty focusing’ and ‘difficulty keeping the eyes open’. Whilst having these symptoms, drivers were more likely to report subjective sleepiness and have line crossings than those who did not suffer the eye conditions. Heavy eyelids and difficulty keeping the eyes open were involved in unintentional line crossings.

Most of us can feel these eye symptoms and could easily make it a rule to stop immediately that any of these eye symptoms appear in a drive. This research is useful validation for users of eye monitoring technology in-vehicles and can be used to set alert parameters.