A research team from German truck maker Daimler recently explored an interesting question in the darkness of Finland’s polar night: Does the biological effect of light have a positive influence on the wellbeing and performance of truck drivers?
Eight Daimler test drivers simulated two typical working weeks for truckers at a site in Rovaniemi, in Northern Finland, in the Arctic Circle.
The truckers alternated between driving for one week in a truck cab with conventional lighting and for another week in a cab with a Daylight+ module that provides additional daylight while driving and during breaks.
In order to ascertain the possible benefits of applying daylight inside the truck cab, project manager and head of the experiment Siegfried Rothe, from the Daimler research department, defined this working hypothesis – that an application of biologically effective light with a wavelength of between 460 and 490 nanometres has a positive effect on humans.
Nobody thinks too much about daylight, provided they do not suffer from a lack of light. Yet light dictates how life on Earth is organised. The shift from day to night provides structure as a short-term time cycle, as do the changing seasons. Also, evolution means that the human internal clock has adapted to these circumstances, with this clock helping in synchronising circadian rhythms.
For many years, scientists have been researching the complex relationships between the availability of biologically effective light and the physical and mental states of human beings.
Various related health problems have been defined. One of the most common is seasonal affective disorder.
A lack of light is a serious problem for many people in Northern Europe, for example, where it barely gets light during the winter months. This can result in reduced performance and a lack of motivation.
Light therapy is a standard method of treating these symptoms.
When looking at trucks in terms of daylight, Rothe determined that the shape of a conventional truck cab allows only a comparatively low percentage of natural light to reach the driver’s light receptors. This finding prompted him to think about possible solutions.
An initial series of experiments with engineers from Daimler’s test drive department proved positive. The subjective condition of all test subjects improved significantly under the influence of an additional dose of light, regardless of the time of day.
Another finding proved surprising – test drivers with more daylight in the cab drove more economically.
During the formal experiments in Rovaniemi, Rothe examined how a driver’s performance changes when he or she is exposed to additional biologically effective daylight under clearly defined conditions.
The extra dose of light took three forms involving different intensities:
• Steady light while driving, whereby the intensity was adjusted to the exterior light level.
• An intense light shower of maximum intensity during the tests, before and after driving.
• Light while reclined, likewise of maximum intensity, during breaks while the driver relaxes.
During the night, the test subjects slept in a normally darkened truck.
The team documented the test results with support from co-researcher Dr Michael Schrauf and the use of electroencephalography, electrocardiography and electrooculography and other physiological measurements, as well as saliva samples, to ascertain levels of the sleep hormone melatonin.
Mental state and professional performance, which are closely related, were examined using standardised psychological test procedures (sustained attention and reaction tests on the computer) and by recording vehicle data through the FleetBoard telematics system.
Rothe estimates that it will take several months to sift and analyse the extensive data from the series of experiments conducted in the Arctic Circle.
“Only then we will be able to make a recommendation as to whether the test findings should lead to changes in the design of cab lighting.”
Initial feedback from the truck test drivers already provided some new insights.
The drivers consistently reported that they perceived the space inside the cab to be considerably more pleasant with the additional light fitting.
“When designing the series of tests, we hadn’t even considered that the space might appear larger,” says Rothe.