Side airbags (SAB) have become common standard safety equipment in modern cars since their introduction to serial production in 1994. While the first systems on the market were thorax side airbags (TSAB) which covered only the chest region the area of protection in lateral impacts was considerably extended with airbags intended to prevent the head from striking against the vehicle interior or external structures. This was attempted either by increasing the size of the side airbag in the top portion with so-called head-thorax side airbags (HTSAB) or separate airbag modules, the head side airbags (HSAB), deploying from the roof rail and intended to protect primarily the head and neck of the occupant, often covering the first and second seat row with one bag. While the latter systems are usually a standard feature on today’s medium-sized and large sedan models, they are often available only as an option for many small and compact car models. The wide-spread availability of side airbags in Europe is in part driven by consumer crash test programs like EuroNCAP which included a lateral impact test with a 950 kg moving barrier from the beginning on and introduced a lateral crash into a fixed pole later for vehicles equipped with side protection measures. While a number of studies have demonstrated the protective effect of frontal airbags there is relatively little body of research on the benefits of side airbags, particularly on the European market. In 2006, Page et al. published a comprehensive review of previous international research in that field. They also presented the results of their own study on side airbags from real-world accidents which was not able to demonstrate a significant reduction of injury risk in lateral crashes. Otte and Hüfner published results of a GIDAS analysis (German in-depth accident study) of lateral crashes occurring between 1999 and 2005. Their study was limited by small case numbers based on which no clear statistical evidence of side airbag protection could be established. A case-by-case analysis was then performed and indicated that side airbags are able to reduce the risk of AIS 3+ injury for the thorax and head, but may increase the frequency of injuries in these body regions, too. Therefore, the question remains whether current side airbag systems which in combination with vehicle structural measures undoubtedly perform well in standard crash test situations provide the same level of occupant protection in real-world collisions scenarios. The present study intends to add to the knowledge about side airbag performance in real-world crashes by using an alternative approach to categorize crashes of comparable severity. The evaluated material is restricted to collisions between motor vehicles and does not take into account single-vehicle crashes resulting in collisions with obstacles or from vehicle roll-overs. For this study, cases from the German Insurers Accident Database (UDB) were analysed. UDB contains approximately 8,000 cases based on data from claim files of German motor liability insurers. Only cases with personal damage and claim costs of at least 15,000 Euros are eligible for documentation in the database. Due to the nature of third-party loss insurance, single-vehicle crashes tend to be under-represented in the material and are therefore not the subject of the present evaluation. Pre-selection criteria were collisions between motor vehicles where a passenger car received damage to the vehicle side severe enough to potentially injure an occupant. Crash opponents included other passenger cars, vans, trucks and buses as well as other heavy vehicles like farm tractors. Collisions in which a motor-cycle struck the side of the passenger car were excluded. Pre-selection of the material yielded 296 cases with an occupant sitting on the side where the impact occurred. No discrimination with regards to the belt status was made because only a small effect on the person was assumed for a near-side lateral impact. Occupants younger than twelve years were excluded from analysis as these will likely differ in height from adult occupants and should be transported in suitable child restraints systems. The case material was further restricted to crashes with sufficiently documented impact location and direction and extent of vehicle damage. Depending on the level of documentation of injuries and side airbag deployment, the number of available cases varied slightly for some specific evaluations. Impact direction and location on the struck vehicle was estimated from sketches describing the course of the accident and the collision situation and from vehicular damage. The severity of damage to the struck vehicle is categorized by the location where the major lateral deformation occurred (forward of the occupant compartment, occupant compartment, rearward of the occupant compartment) and the depth of intrusion. The latter was assigned a “degree of damage” as regularly used in analyses of the UDB database. With this method, actual damage of a vehicle is compared to a standard set of sample pictures to categorize intrusion depth in degrees ranging from DoD1 for small deformation and DoD2 for moderate intrusion to DoD5 with massive deformation. Side airbag deployment was determined from scene photos or repair documentation. Where no airbag deployment could be established, this may have been due to either a vehicle with a side airbag, but which was not fired, or a vehicle not fitted with a side airbag. These two reasons for non-deployment were not discriminated when cases without deployment were considered. Injury severities were coded according to AIS 98 (Abbreviated Injury Scale) and the highest AIS value for separate body regions was determined for near-side occupants as well as their MAIS value (Maximum AIS). The effect of a side airbag is estimated by comparing injury outcomes in the group of lateral crashes with deployed side airbag with the group of lateral crashes without deployed side airbag, or without fitted side airbag, respectively. (Author/publisher)
Samenvatting