Seating and sleeping comfort in transit: Recommendations on human activity-based research and design for vehicle seats

The interior design of vehicles is evolving rapidly due to technological advancements, sustainability demands, and shifting user behaviors. Vehicle interiors need to become lighter to reduce energy consumption while maintaining comfort levels. The rise of global trends such as automated driving, new propulsion methods in aviation, and the increasing popularity of long-distance and sleeper trains necessitate innovative interior designs. These designs should enable productivity, relaxation, and sleep while in transit.

This doctoral dissertation provides design guidelines for creating comfortable and practical seating and sleeping environments in various vehicles, including trains, aircraft, automated cars, ships, and submarines. The research emphasizes the importance of considering human activities and the effects of time when studying comfort and discomfort. It highlights that factors like prior activities, movements during tests, postures, and awareness of time can all influence comfort levels. The findings show that discomfort tends to stabilize or decrease over time, while comfort tends to stabilize or increase, particularly as participants become aware of the test duration.

One approach to designing comfortable, lightweight seats is to base them on the human contour. By using 3D scans to map the human body, material can be reduced without significantly affecting comfort. This method has been successfully applied to aircraft seats in various classes, demonstrating that weight and volume can be reduced while maintaining or even improving comfort. Additionally, optimizing pressure distribution, using porous materials, and employing topology-optimized structures can further reduce seat weight and enhance comfort. These advancements are crucial for reducing the environmental impact of future vehicle interior designs.

Sleeping is a critical activity for long-haul passengers, but it is often challenging in transit. The dissertation explores sleep in a full-flat position, noting that while people need space to move during sleep, limited space in vehicles can negatively impact sleep quality and comfort. Although space can be reduced by about 25% without severely compromising sleep quality, designers must carefully balance the sleep space envelope with other factors such as economics, weight, and operational safety.

Another common activity in vehicles is watching in-vehicle entertainment (IVE) or napping in a reclined seat. The research shows that while people prefer a slouched posture for watching IVE, this position often lacks proper head and neck support. Although a headrest can improve comfort, it does not necessarily reduce muscle activity. A head sensitivity model developed in the dissertation suggests that high pressures around the ear, temple, and neck should be avoided, and that most of the head's load should be supported by the back of the head and the jawline.

The dissertation’s main research question explores the physical ergonomic factors that influence seating, relaxing, and sleeping comfort. The findings show that considering human contours, sensitivity, behavior, and time can lead to more comfortable and effective seating and sleeping environments in vehicles. While the dissertation makes significant strides in understanding these factors, further research is needed to develop more detailed guidelines, particularly for designing sleeping environments in transit. The research concludes that seat design should be activity-based, accommodating natural behaviors and posture variations to enhance user comfort and safety.