Sleep quality and comfort in an automated vehicle

Automated vehicles will offer occupants new ways to utilize their time. One of the greatest opportunities offered by automated driving is sleeping and relaxing in the car. However, a comfortable seating position is required to relax during a car journey. Currently, there are only a few ideas and design proposals on how a seat must be configured to promote and ensure a comfortable sleeping position. In collaboration with a German OEM, a study was conducted to answer this question.

The customer brought two different configurations of a seat for evaluation. The first position was in a reclined position, the second position was almost fully reclined. The seat had already been evaluated by the customer's previous work in terms of material and construction.

The seat was in a car of the OEM and was parked in a garage of the Fraunhofer IAO, where the study took place. The participants were required to sleep in the car twice, once in each position of the seat, for a total of four hours. To ensure a realistic simulation of the driving experience, the car windows were darkened, the lights in the room and in the car were switched off, and a realistic acoustic environment was created by playing the sound of a real car travelling at 100 km/h on a smooth road through the car's loudspeakers.

As part of the study, a polysomnography was conducted, during which EEG (electroencephalography), EOG (electrooculography), and EMG (electromyography) were recorded. In addition, subjective data was collected before and after the study in the form of questionnaires and a sleep diary.

The analyses revealed that participants in the almost fully reclined position had significantly more deep sleep compared to the reclined condition. Additionally, there was a non-significant trend indicating an earlier onset of deep sleep compared to the reclined position.

The general sleep onset occurred significantly earlier when the seat was almost fully reclined.

The results demonstrate that a flat lying position provides greater comfort and relaxation for test subjects than a reclined position.