User experience and occupant safety : Concept development of restraint system for the automobile outboard rear seat positions

Sammanfattning: This is a master thesis project that is made in collaboration with Volvo Car Corporation, at the seat belts & child restraints department, located in Gothenburg, Sweden. The project description and objective of this project was to develop a concept, for the rear outboard seat positions, that makes the seat belt comfortable without compromising the safety with the focusing point on user experience. The safety systems of the car can be divided into two groups, active safety systems, and passive safety systems. The active safety systems help to prevent accidents from occurring and the passive safety systems are there to protect the occupants from serious injury in the event of an accident. Passive safety systems include airbags and seat belts, which are required by law in most countries. The seat belt system is the primary restraint system in the car. A challenge with current seat belt systems is to make one single seat belt geometry that fits all users optimally. A less than optimal seat belt geometry could lead to the belt rubbing against the neck with the possibility of misuse as a consequence or being positioned too far out on the shoulder, which makes the risks of torso rollout and injuries increase.The safety in the rear seat has been prioritized recently due to the new requirements stated by European New Car Assessment Programme, which is a new car assessment programme, that tests and evaluates different safety aspects of cars. Another reason is Volvos vision that no one should be killed or seriously injured in a new Volvo car by 2020, which is a continuous ongoing work of improving safety.This project has used a combination of the stage-gate process and a prototype-based process, which enabled prototype building and testing throughout the whole development. The Stage-Gate process was divided into 4 stages. These stages were Context immersion, Ideation, Implementation, and Finalization. At the end of each stage, there is a gate, meaning some things that needed to be delivered to Volvo Cars before proceeding on to the next stage.The work resulted in two concepts that are based on two different principles. Concept Ridge is a concept where the seat belt automatically adjusts to the occupant. The concept is based on that occupants with shorter torso needs a more outboard position in order to prevent the seat belt rubbing against their neck. It works by having a slanted surface placed on top of the seat that ‘guides’ the seat belt into an outboard position. If the occupant has a tall torso the shoulder belt barely touches the surface and therefore moves to its default inboard position. Ridge has been tested and evaluated with both crash test dummies and people with different statures and proportions since the crash dummies do not reflect people in reality.The other concept, Soft, is based on only having one static position and instead make the seat belt comfortable by covering it with a soft tube. Soft has the advantage of making the belt comfortable even when it is located in a safe position close to the occupant’s neck.