Researchers from the University of Granada in Spain have shown that individual chronotype - that is, whether you are a "morning-type" or an "evening-type," depending on the time of day when your physiological functions are more active - markedly influences driving performance.
The study found that evening-types are much worse drivers - they pay less attention - at their "non-optimal" time of day (early in the morning) compared to their optimal time (during the evening).
In the experiment morning-types were more stable drivers than evening-types and drove relatively well both in the morning and the evening.
Researchers from the Neuroergonomia research group of the University of Granada Mind, Brain and Behavior Center, analysed the circadian (biological) rhythms in a sample of 29 University of Granada students with extreme chronotypes, selected from a database sample of over 500.
Researchers used a questionnaire to determine issues such as when participants were most energetic or what their sleeping habits were, and a driving simulator.
So, both the morning- and the evening-types were made to drive at 8.00 in the morning and 8.00 in the evening. Then they compared their driving performance at their respective optimal and non-optimal times of day.
In the light of the results, the researchers suggest that businesses should test workers to determine whether they are morning- or evening-types and adapt work schedules to suit chronotypes.
"Certain professions involve performing tasks that require good attention vigilance - airline pilots, air traffic controllers, supervisors in nuclear power stations, surgeons, or lorry drivers," said Angel Correa, principal author of the study.
"A particular time of day can be a good or a bad time to perform these tasks as a function of the chronotype of the individual involved, although there are times that are bad for everyone, like siesta time or in the early hours between 3.00 and 5.00," Correa said.
Researchers warn that driving after more than 18 hours wakefulness - say, at 2.00 in the early morning after waking at 8.00 the previous morning, which is quite common - "entails the same level of risk as driving with the legal maximum level of blood alcohol, because our level of vigilance declines considerably."