To establish guidelines for sleeping space in vehicles, the sleeping postures of 189 participants are studied, 105 of them were asked to take the position in which they fall asleep and 84 have been asked to assume the position in which they lie most of the time. Seven percent slept on the stomach, 19% on the back and 74% on the side and 49% slept on the side with both legs flexed. For all participants a bed size of 200 × 90 cm will do. It is discussed that for one night while travelling a bed size of 171 × 76 cm might be sufficient as it results in a reasonably good sleep according to another study and in almost half of the cases in this study people sleep on the side with both legs folded. Apart from the sleeping space for a good sleep, attention is needed for a dark environment with a good temperature and relative silence.@en

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.@en

When designing wearables that interface with the human head, face and neck, designers and engineers consider human senses, ergonomics and comfort. A dense 3D pressure discomfort threshold map could be helpful, but does not exist yet. Differences in pressure discomfort threshold for areas of the head, neck and face were recorded, to create a 3D pressure discomfort threshold map.

Between 126 and 146 landmarks were placed on the left side of the head, face and neck of twenty-eight healthy participants (gender balanced). The positions of the landmarks were specified using an EEG 10–20 system-based landmark-grid on the head and a self-developed grid on the face and neck. A 3D scan was made to capture the head geometry and landmark coordinates. In a randomised order, pressure was applied on each landmark with a force gauge until the participant indicated experiencing discomfort. By interpolating all collected pressure discomfort thresholds based on their corresponding 3D coordinates, a dense 3D pressure discomfort threshold map was made.

A relatively low-pressure discomfort threshold was found in areas around the nose, neck front, mouth, chin-jaw, cheek and cheekbone, possibly due to the proximate or direct location of nerves, blood veins and soft (muscular) tissue. Medium pressure discomfort was found in the neck back, forehead and temple regions. High pressure discomfort threshold was found in the back of the head and scalp, where skin is relatively thin and closely supported by bone, making these regions interesting for mounting or resting head, face and neck related equipment upon.@en

This paper investigates whether spring-foam technology in an aircraft seat-pan can reduce weight and at the same time provide equal or better comfort. Firstly, through literature studies and using an iterative design process a prototype seat-pan was designed and developed using spring-foam technology. The (dis)comfort of this seat was compared with a standard aircraft seat-pan. Twenty two participants were asked to sit in each seat for 90 min, completing a questionnaire every 15 min. At the end of each seating session pressure map recordings were made of the seat-pans. The results showed that the prototype seat-pan has on average a significantly higher comfort for the first 30 min and at a 60 min recording than the standard seat-pan. The discomfort and long term comfort were not significantly influenced. The pressure distribution on the prototype seat-pan was significantly closer to an ideal pressure distribution than a conventional seat-pan. In addition, the prototype seat-pan had a significantly larger contact area and lower average pressure. The seat-cushion weighs 20% less than the conventional seat-cushion. The study indicates that a seat-pan design using spring-foam technology can be lighter and more comfortable than conventional foam cushion materials. It is recommended to optimize the prototype seat further and conduct long term (dis)comfort studies with a broader variation in subjects’ age.

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Sleep facilities in aircrafts, trains, busses, ships, submarines, (autonomous) cars, and other vehicles often have a limited space due to economic and/or operational reasons. Providing an effective and comfortable sleep is important for passenger satisfaction (e.g. to justify surplus prices) and crew effectiveness and operational safety (e.g. in operational safety critical environments such as aircraft cabin crews, medical staff, offshore and maritime workers and military personnel. Forty-one participants were asked to score the experienced sleep quality – by means of the Pittsburgh Sleep Quality Index (PSQI), the Karolinska Sleepiness Scale (KSS), the Samn-Perelli 7-point Fatigue Scale (SPFS) and a Rested Scale – and (dis)comfort after a night sleep in three conditions: Night 1) in their normal bed space (the bed they sleep in in their house, which was usually 190-200 cm long and 90-140 cm wide), Night 2) in a limited space (170 x 70 cm), and Night 3) in a minimal space designed by the participant (a bed space which is limited, but still rather comfortable, based on own insight and their experiences from nights 1 and 2). The average comfort and discomfort scores differed significantly (see Figure 1). In their normal bed space (night 1) the comfort score was 3.96 (scale 1-5; 5=maximum comfort; sd= 0.73) and in a limited space (night 2) 2.59 (SD=0.91), and in their normal bed space (night 1) the discomfort was 1.53 (scale 1-5; 5=maximum discomfort; sd= 0.60) and in the limited space (night 2) 2.98 (SD=0.86). The designed space varied a lot (see Figure 2): the minimal width was 46 cm and the maximum was 140 cm, and the length varied from 100 to 200 cm. The mean designed sleep space was 166 x 78 cm. Perhaps the p75 is here a more relevant value which was 186 x 90 cm, which seems still rather large and not appropriate for vehicles like cars, submarines, trains and airplanes.@en

A proper seat is crucial not only for preventing health issues but also for the (dis)comfort perception. In the design of a seat, the seat pan’s geometric shape, either in or under the cushion, plays a vital role as it constrains the deformation of the foam it supports. The contact area and pressure distributions between the foam and the human body, closely associated with (dis)comfort, are influenced by those constrained deformations. In this paper, using a comparative study, the aim is to determine if opportunely shaped seat pans are better than a standard flat pan regarding postural comfort and pressure distribution. Two cushions with the same type of foam but two different seat pans were used in the comparison. The first seat pan is the standard one used in current aircraft seats and the second is a shaped seat pan, which was designed following the mean buttock-thigh shape of an international population (including P5 females and P95 males). Twenty-two international participants (11 males and 11 females, with BMI between 16 and 30) took part in the blind experiment. Results indicated that the cushion with shaped seat pan performed better as it led to less postural comfort, a larger contact area and more uniform pressure distribution. Also, 64% of participants favored the cushion with the shaped seat pan as they felt it was more comfortable and suitable for the buttock shape.@en

(Dis)comfort research that has no information on behaviour of the participants can be considered as incomplete, as major influencing factors could be missed. For (dis)comfort research it is important to capture influential factors such as context and task/activity, posture, movement, (distracting) stimuli and time, as these factors have influence on the experienced (dis)comfort. Recording the behaviour allows for better evaluation of and comparison between studies, contributing to an increase of scientific knowledge on (dis)comfort.@en

The percentage of passengers that prefer travelling in groups is increasing. In most vehicles, passengers sit side by side and need to turn their body to be engaged in the conversation with their fellow travellers. However, rotating the body could lead to discomfort which influences conversation quality. The aim of this research is to study the effect of seat configuration on the (dis)comfort experience, conversation quality and posture. Experiments in which participants were asked to talk to each other while sitting at the same distance (1 m) were conducted in four seating arrangements (with seat-belts on), where the angle between the forward directions of two seats were positioned at 0° (side by side), 22.5°, 90° and 120° (almost opposite each other), respectively. Optical tracking has been deployed and the collected data were processed with MatLab^® to acquire postural angles over time. Questionnaires were also used to evaluate the perceived (dis)comfort and the quality of the conversation. Experiment results indicate that the 120° configuration scored the best in the overall comfort and the quality of conversation, but only slightly better than the 90° configuration. Practitioner summary: Seating side by side is not optimal to have a comfortable conversation with your seatmate. To improve comfort and quality of conversation in future vehicles, we tested four seating arrangements analysing the effect of seat layout on (dis)comfort experience. Statistical analysis of objective and subjective data shows the optimal configuration for a comfortable conversation. Abbreviation: LPD: localized postural discomfort; PDF: probability density function; OCRA: occupational repetitive action.

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This research aims to study the effect of seat and/or backrest rotation on comfort and quality of conversation. Different sitting arrangements were tested to study the effect of the seat layout on: 1) (dis)comfort experience; 2) conversation quality and 3) postures. Two seats were arranged in different angles (0° 45° 90° and 180°) at the same distance (1 m) and participants were asked to talk to each other. The participants’ postures were acquired by using cameras and markers on the participants’ body. Questionnaires were used to rate the perceived (dis)comfort and quality of conversation. Results show that 90° configuration scored the best both in overall comfort and quality of conversation; while the 0° configuration scored the lowest in both ratings. A strong correlation was established between high comfort and good quality of conversation.

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The purpose of this study is to research if a headrest benefits the comfort of the passenger and lowers muscle activity in the neck when sitting in a reclined (slouched)posture while watching in flight entertainment (IFE)in an aircraft business class seat. No significant differences in muscle activity in the musculus sternocleidomastoid and musculus trapezius pars descendant were found between the conditions with headrest and without headrest. A significant difference in expected comfort rating was found. Subjects indicated they expect to experience more comfort with a headrest when watching IFE for a duration of two movies during a long-haul flight. This study also found a significant difference in posture. In the condition without headrest the head was more upright compared to the condition with headrest. The lack of significant difference in muscle activity and the significant difference in posture may indicate that humans tend to look for a head position that is neutral, in the sense of minimal muscle effort. This study shows that the use of a headrest may benefit the comfort experience of the passenger during flight. However, further research is necessary on the design of the headrest and the long-term effects of head support on comfort, discomfort, muscle activity and fatigue for watching IFE in a slouched posture.

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To save fuel costs, lightweight designs and materials are preferred for aircraft interiors. One of the challenges for aircraft seats is to reduce weight without compromising passenger comfort, or perhaps even while increasing comfort. This case study describes three different projects on lightweight designs for aircraft seats, using three-dimensional (3D) scanning methods (Franz, Kamp, Durt, Kilincsoy, Bubb, & Vink, 2011) to determine the ideal seat contour following the human body. The first project on upright sitting in an economy aircraft seat (Hiemstra-van Mastrigt, 2015) set out to collect imprints of the human body in a vacuum mattress by using a handheld 3D scanner to scan the body imprints and obtain a 3D surface. Subsequently, the different scans were superimposed in such a way that differences between the scans were minimized. Based on this “ideal curvature,” an adjustable seat pan concept was developed (Kuday, 2018). A similar 3D scanning method was applied in two other projects: first, developing a prototype for passengers sleeping sideways in a premium economy class aircraft seat (Lam et al., 2014) and, second, a human contour-based business class seating concept (Smulders et al., 2016). This case study concludes with advantages and recommendations for applying 3D scanning in similar projects.

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BACKGROUND: The concept of comfort is one way for the growing airline market to differentiate and build customer loyalty. This work follows the idea that increasing the contact area between human and seat can have a positive effect on comfort [5, 6, 7]. OBJECTIVE: To improve comfort, reduce weight and optimise space used, a human contour shaped seat shell and cushioning was developed. METHODS: First the most common activities, the corresponding postures and seat inclination angles were defined. The imprints of these postures on a rescue mat were 3D scanned and an average human contour curve was defined. The outcome was transferred to a prototype seat that was used to test the effect on perceived comfort/discomfort and pressure distribution. RESULTS: The resulting human contour based prototype seat has comfort and discomfort scores comparable to a traditional seat. The prototype seat had a significantly lower average pressure between subjects' buttocks and the seat pan over a traditional seat. CONCLUSIONS: This study shows that it is possible to design a seat pan and backrest based on the different contours of study subjects using 3D scan technology. However, translating the 3D scans into a prototype seat also showed that this can only be seen as a first step; additionally biomechanical information and calculations are needed to create ergonomic seats. Furthermore, it is not possible to capture all different human shapes and postures and translate these into one human contour shape that fits all activities and all human sizes.

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