Comfortable car interiors: Experiments as a basis for car interior design contributing to the pleasure of the driver and passengers

One of the main challenges for car manufacturers is complying with the stringent environmental regulations without compromising driving comfort and pleasure. Reducing the overall weight of a car reduces fuel consumption and increases acceleration. However weight reduction seems in contradiction with another important aspect of car-sales; comfort. In this PhD thesis five experiments are presented proving that weight reduction and comfort improvement can go hand in hand. In these studies specific details for car interior design are described and a conceptual model is created to generalize the outcomes. First the concepts comfort, pleasure and well-being are discussed and a model is created to describe, develop and understand products contributing to the well-being of humans. This model is illustrated in two studies focusing on improving the driving experience of the driver while reducing the overall weight of the car. In the first study a rather comfortable seat based on the human surface anatomy is developed with a new patented technique using 3d scanning of the human contour. A seat form following this contour is developed and compared to a traditional seat. Occupants liked the “contour seat”, which was almost half the weight of a normal seat. In the second study an additional experiment was performed. To improve the driving experience, a seat should elicit the same feeling as the car exterior communicates e.g. a seat in a sports car should feel sporty. This study describes the contours of three different car seats objectively and records the corresponding emotional and tactile experiences of people sitting in them. The results show that hard seats with rather high wings in the seat are rated sporty and seats that are softer are rated more luxurious. Three other studies focus on the passenger. The goal of these studies was to make the rear seat more pleasurable without adversely affecting the weight of the car. What people want to do and how they sit during travel and leisure situations was investigated in the first study. Low and medium level activities like watching, talking/discussing and reading were observed the most. The analysis suggests a significant relationship between the activity and the position of the head, trunk and arms during transportation situations. When designing rear seats facilitating low level activities like sleeping and relaxing, adequate support for head and arms is important. For medium level activities the back seats should offer freedom of movement. The next study describes the development of a new lightweight way of entertaining the passenger in the rear seat. To create a new environment experience the road ahead was projected onto the back of the front seat. A test with a simple prototype showed that driving with road projection was rated more pleasant and the interior was experienced as less confined. However the feeling of safety decreased. In future research an improved, more automotive specific prototype should be tested on various road-conditions, but the results of this first user test are promising. Another innovation which was intended to improve the passengers’ driving experience, was an extension of the current massage system. With this new system the passenger can control a game with his upper body by pressing the shoulder in the back seat. The effects of these movements were compared to normal car activities and a difference in muscle activity and variability were found. It is comparable to moderate intensive activity based on a preliminary heart rate study. The discomfort ratings of all activities are low but subjects felt more challenged during the ride and fitter and more refreshed afterwards only when using the active seating system. Although improvements for the current prototype were discovered during this study the results show that active seating has much potential for improving comfort. Connecting the studies to the conceptual models at the beginning of the thesis leads to the conclusion that, opposed to the more general character of discomfort, comfort is very personal. Hard seats and bad smells are experienced as uncomfortable by most drivers and passengers. However it depends strongly on the personal goals, values, wishes (concerns) etc. of users whether road projection or active seating makes a car comfortable or pleasurable. So, generalisation of this statement is more difficult. Therefore the advice for product design in general and car manufacturers in particular is to look at the human concerns of the target group and try to develop hedonic product attributes to create personal products or systems that can be turned on and off. Another conclusion is that limitations in a design process, such as stringent environmental regulations in the car industry, can also be seen as great triggers for innovation. It is not only challenging for designers, but higher management is often very committed to innovations based on external forces like regulations or better competitive products. This thesis has given examples of design-ideas that can improve the comfort and pleasure experience for drivers and passengers while reducing the weight of the car and therefore contribute to environmental friendlier cars with comfortable car interiors.