Researchers from the Universite Bordeaux Segalen, France, and their Swedish colleagues conducted tests in real driving conditions.
Blue light is known to increase alertness by stimulating retinal ganglion cells: specialised nerve cells present on the retina, a membrane located at the back of the eye.
These cells are connected to the areas of the brain controlling alertness. Stimulating these cells with blue light stops the secretion of melatonin, the hormone that reduces alertness at night.
Sleepiness is responsible for one third of fatalities on motorways as it reduces a driver's alertness, reflexes and visual perception.
The researchers' findings, published in the journal PLoS One and reported on the Medical Express website, used a special LED lamp continuously emitting blue light installed on the dashboard of an experimental vehicle.
To study the efficiency of blue light during night driving, researchers asked 48 male volunteers (average age 33.2) to drive 400km on a motorway, the 'Daily Mail' reported.
Each driver completed three night drives, spaced out by at least a week, between 1am and 5:15am, with a 15-minute break halfway through the journey.
During each of the three nights, the volunteers were either exposed to continuous blue light, or given two cups of coffee (one before departure and one during the break).
These either contained 200 mg of caffeine or were decaffeinated, representing a placebo. The researchers found that drivers' sleep was not affected following the journeys with exposure to blue light.
They then analysed the number of times that a driver encroached on road markings (hard shoulder or centre line), reflecting a decrease in alertness.
The results of this test showed that on average, the line was accidentally crossed 15 times by the drivers exposed to blue light, 13 times by those who had had coffee and 26 times by those who had had the placebo.
Continuous exposure to blue light while driving therefore appears to be as efficient as coffee for fighting sleepiness at the wheel, as long as this light does not hinder the driver.
However, eight of the 48 volunteers (17 per cent) found that they were dazzled by the blue light and could not do the test.
The researchers are now verifying these first results by making a test on a larger number of subjects, including women and the elderly.
