Most people other than Eskimos and Finns take daylight pretty well for granted, as long as the sun rises every morning. But light determines how life is organised, and regulates our internal clocks.
Lack of light is a serious problem in Northern Europe; it’s called seasonal affective disorder, and light therapy is a standard method of treating these symptoms medically.
To find out whether this would work for truck drivers, Daimler research scientist Siegfried Rothe and eight test drivers spent two weeks in the darkness of Finland’s polar night, simulating typical winter working conditions. The drivers alternated between driving one week in a truck cab conventional lighting and a another week in one with a Daylight+ module that provides additional daylight while driving and during breaks.
Roche defined the parameters of his research as the application of biologically effective light with a wavelength between 469 and 490 nanometres, and designed a sophisticated series of experiments to test his hypothesis.
The idea for Daylight+ came out of a research project in the sleep lab at the University of Regensburg. Rothe, who’s involved in a number of projects aimed at improving working conditions for truckers, found that because of the box-like shape of a conventional truck cab, only a small percentage of ambient daylight reaches the driver.
So he experimented with engineers from the test drive department and found that all their performances improved across the board with brighter lighting, regardless of the time of day – and to his surprise, he also found that the test drivers with more daylight in the cab drove more economically.
When they moved to real-world testing in snowbound Finland, the drivers were tested only against themselves; researcher Dr Michael Schrauf used electroencephalography, electrocardiography and electrooculography, as well as saliva samples (to record their levels of the sleep hormone melatonin) to measure their performance on standardised psychological tests for sustained attention and reaction time on a computer, and by analysing their driving using onboard telematics. During the night, the drivers all slept in a normally darkened truck.
At the end of each two-week cycle, the drivers were interviewed; the two drivers who spent time in Rovaniemi at the darkest time of year – just before Christmas – Richard Schneider and Philippe Strasser, both said the Daylight+ module made the tough driving conditions easier to manage.
But all eight drivers surprised Rothe by saying that the extra lighting made the inside of the cab seem more pleasant and also that it felt bigger!
“We didn’t even consider that,” admitted Rothe; once he’s analysed the data from the arctic tests, he’ll be able to make recommendations that could possibly change how truck cabs are lit inside.