Run Off Road Safety

Run off road events are frequent and can result in severe consequences. The reasons for leaving the road are numerous and the sequence the car is subjected to differs in most events. The aim of this study is to holistically address safety improvement in run off road events, presenting methods for evaluation as well as examples of countermeasures for the whole sequence from normal driving to post-crash. Real world data, comprising statistical and in-depth crash data as well as driving data from Volvo Cars’ database in Sweden, forms the basis for understanding of influencing factors and mechanisms related to occurrence of the event as well as occupant injury. Countermeasures are presented along with the test methods which were developed based on the mechanisms identified. The test methods include road off road avoidance test methods, complete vehicle crash tests, and rig tests; such as occupant positioning using a robot rig and vertical loading tests using a drop tower rig. Countermeasures addressing run off road safety are developed and verified using the identified test methods and integrated into vehicle design. Examples of systems addressing road departure avoidance aspects are Driver Alert Control and Lane Keeping Aid. Countermeasures specifically addressing occupant protection are occupant positioning by detecting run off road events and activating an electrical reversible safety belt pretensioner, as well as unique energy-absorbing functionality in the seat. Post-crash measures are enhanced by added activation of eCall in some run off road scenarios. Optimally, avoiding the run off road is most beneficial and this study provides some initial steps illustrated by production systems. However, if run off road occurs, one priority is to reduce vertical occupant loadings when landing on the wheels after a free-flight, a rollover or when going into a ditch and impacting an embankment. This type of loading could result in thoracic-lumbar spine fractures. The design of the unique energy absorbing functionality in the seat, put into production 2015, will help provide important enhanced occupant protection. Additionally, injury outcome is influenced by the occupant position during the event: head and arms flinging around impacting the interior, bent postures reducing the tolerances of spinal injuries, and sub-optimal occupant positioning relative to protection systems. The unique run off road detection and safety belt pretensioning early in the events, together with the seat backrest’s side supports, will assist the occupant to stay positioned during the event and help improve protection. This study is based on a holistic approach to safety, covering the whole event from normal driving to crash care, introducing world first production technology enhancing occupant protection in these diverse and complex events. It goes beyond standardized safety evaluation of today and it provides an illustrative example on how safety systems can take action across the entire crash sequence and the interaction of different types of systems adding to the effect of addressing real world protection needs.