Real-time Driver Drowsiness Feedback Improves Driver Alertness and Self-reported Driving Performance

The intervention was infra-red oculography-generated feedback of drowsiness level. Drivers wore glasses fitted with a device which uses infra-red wavelengths directed at the eyelid to measure eye blink characteristics. The data was used by the system under test to calculate a near real-time score which indicates a person's level of drowsiness. A drowsiness score is generated every 60 seconds. For the intervention, this drowsiness score is presented to the driver via a dashboard mounted numerical LED display. Participants are able to view their drowsiness levels whilst driving via a dashboard-mounted LED display. Drivers had their drowsiness levels recorded whilst driving in a naturalistic setting including sessions of off-duty driving in their own vehicles, commuting to and from work in private vehicles, and duty driving in military vehicles. As such, duration and frequency of driving sessions varied and were neither prescribed nor controlled. It was expected that drivers would complete at least two driving sessions per day for the period of the trial (8 weeks) and be a mixture of private and duty driving. The intervention had two conditions; feedback ON and feedback OFF. Each participant experienced one of the conditions during each of their naturally occurring driving sessions for a period of four weeks. At the end of the four weeks the participant was switched to the other condition for the remaining four weeks. The order of conditions was counterbalanced such that roughly equal numbers of participants were in each condition within a four week period. There was no follow-up period as the intended effects (reduced drowsiness whilst driving, improved driving performance) of the intervention (drowsiness level feedback) were transient phenomena of interest and not ongoing beyond the duration of the intervention. There was no washout period. Participants transitioned from one condition to the other in the space of a few minutes as there were no ongoing effects of being in one condition or the other.