Yngve Haland

Neck injuries in car collisions — a review covering a possible injury mechanism and the development of a new rear-impact dummy

A review of a few Swedish research projects on soft tissue neck injuries in car collisions is presented together with some new results. Efforts to determine neck injury mechanisms was based on a hypothesis stating that injuries to the nerve root region in the cervical spine are a result of transient pressure gradients in the spinal canal during rapid neck bending. In experimental neck trauma research on animals, pressure gradients were observed and indications of nerve cell membrane dysfunction were found in the cervical spinal ganglia. The experiments covered neck extension, flexion and lateral bending. A theoretical model in which fluid flow was predicted to cause the transient pressure gradients was developed and a neck injury criterion based on Navier-Stokes Equations was applied on the flow model. The theory behind the Neck Injury Criterion indicates that the neck injury occurs early on in the rearward motion of the head relative to the torso in a rear-end collision. Thus the relative horizontal acceleration and velocity between the head and the torso should be restricted during the early head-neck motion to avoid neck injury. A Bio-fidelic Rear Impact Dummy (BioRID) was developed in several steps and validated against volunteer test results. The new dummy was partly based on the Hybrid III dummy. It had a new articulated spine with curvature and range of motion resembling that of a human being. A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure.

THE INFLUENCE OF SEAT-BACK AND HEAD-RESTRAINT PROPERTIES ON THE HEAD-NECK MOTION DURING REAR-IMPACT

The influence of different seat properties on the head-neck motion during a low-velocity rear-end impact was tested using a Hybrid III-dummy fitted with a modified neck (RID-neck). The results show that by modifying the properties of the seat-back and head-restraint it is possible to influence the head-neck kinematics to a great extent. It was possible to virtually eliminate the neck extension motion during a rear-impact. This will hopefully result in a significant decrease in neck injury risk in real world rear-impacts.

Life-threatening and disabling injuries in car-to-car side impacts—implications for development of protective systems

Improvements to the passive safety of cars in lateral collisions are of great importance. This study of injuries in car side collisions in Sweden by the use of two evaluation methods has been performed to establish the basis for future development of protective systems for this type of accident. The Folksam car accident data file has been used. Injuries were found to be twice as common for near-side than for far-side* occupants in car to car impacts. Serious to fatal (AIS 3-6) injuries to belted front seat occupants in near side impacts (10% of all injuries) were compared with the estimated number of injuries to different parts of the body with risk of serious consequences (RSC)--either deaths or permanent disabilities (4.5% of all injuries). The two injury evaluation methods resulted in different ranking orders. AIS 3-6 injuries were received by the chest (37%), abdomen/pelvis (25%), and the head (15%). The RSC method gave a ranking order of head (25%), neck (21%), leg (15%), chest (14%), and abdomen/pelvis (11%). The method of evaluating AIS 3-6 injuries emphasizes only the threat to life. The RSC method also takes into account the risk of disabilities. Injuries to the neck and the leg were found to be most disabling, whilst the injuries to the head, chest, and abdomen/pelvis were the most life threatening. The study also shows that elderly people receive significantly more chest injuries (relative to the number of head injuries), on average four times more than young people.(ABSTRACT TRUNCATED AT 250 WORDS)

A parametric study of a side airbag system to meet deflection based criteria

A side airbag system comprising of 12 liter bag to cover the BioSid chest and the abdomen down to the arm rest level, and 75 mm of padding to cover the pelvic/thigh area was evaluated by a series of sled tests at two different velocities, 10 m/s and 12 m/s. The initial bag (over) pressure was varied from 0 to 80 kPa and the bag ventilation area was varied from zero to 1500 mm2. Compressed air was used to fill the bag. It was found that the ventilation of the bag reduced the maximum chest deflection by 30 percent and the maximum viscous criterion, VC, by 50 percent (comparison was made with the same bag without ventilation). A suitable initial bag (over) pressure was found to be about 50 kPa, when the loading of the abdomen was also taken into consideration. The results indicate that the chest deflection is proportioned to the door average velocity (during the first 20 ms of deflection) to the power of about 2 and that the VC is proportional to the same velocity to the power of about 4. It was also found that a 12 liter ventilated side airbag resulted in 30-40 percent lower chest deflection and about 60 percent lower VC than 50 mm of chest padding (Ethafoam 220).

Frontal impact dummy kinematics in oblique frontal collisions: Evaluation against post mortem human subject test data

Objective. Today, a predominant percentage of vehicles involved in car crashes are exposed to oblique or frontal offset collisions. The aim of this study is to evaluate the 50th percentile male Hybrid III, THOR 99, and THOR Alpha dummies by comparing them with the corresponding kinematics of post mortem human subjects (PMHS) in this type of collision. Methods. The PMHS data include results from oblique frontal collision tests. They include sled tests with near-side and far-side belt geometries at 15°, 30°, and 45° angles. The test subjects were restrained with a three-point lap-shoulder belt and the Δ V was 30 km/h. Results. The results from the Hybrid III and THOR 99 tests showed that, in most of the test, the head trajectories were an average of approximately 0.1 m shorter than those from equivalent PMHS. The Hybrid III and THOR 99 far-side belt geometry tests showed that the belt remained in place longer on the shoulder of the Hybrid III than on the THOR 99 and the THOR Alpha. This was probably due to a stiffer lumbar spine in the Hybrid III and to a large groove in the steel of the superior surface of the Hybrid III shoulder structure. The THOR 99 escaped from the shoulder belt about 40–50 ms earlier than the THOR Alpha. The results from the THOR Alpha tests show that the head trajectory accorded fairly well with the PMHS data, as long as the shoulder belt did not slip off the shoulder. Although the THOR Alpha shoulder escaped the shoulder belt in the 45° far-side belt geometry, the PMHS did not. This may be due to the THOR Alpha shoulder design, with approximately 0.05 m smaller superior and medial shoulder range-of-motion, in combination with a relatively soft lumbar spine. Conclusions. The THOR Alpha provides head trajectories similar to those of the PMHS under these loading conditions, provided the shoulder belt remains in position on the shoulder. When the shoulder belt slipped off the dummy shoulder, the head kinematics was altered. The shoulder range-of-motion may be a contributing factor to the overall kinematics of an occupant in oblique frontal impact situations where the occupant moves in a trajectory at an angle from that of the longitudinal direction of the car.

Benefits of a 3+2-point belt system and an inboard torso side support in frontal, far-side and rollover crashes

3-point belted occupants are still being injured in numerous crashes. In frontal collisions this is partly explained by the range of hard tissue tolerance amongst car occupants. In side collisions occupants on the far side of the intrusion are mainly restrained by the lap part of the 3-point belt, with an associated high risk of sustaining a severe head injury. During a rollover crash the 3-point belt cannot fully prevent harmful head impacts. In this study an additional 2-point belt (single handed optional operation) is combined with an inboard torso side support. The idea is simply to distribute the belt load on more anatomical structures (bones) as well as constituting a non-injurious inboard and upward restraint. The inboard side support prevents a direct loading by the 2-point belt to the cervical spine in far-side collisions. It also supports the torso when the 2-point belt is not buckled. To prove if this design measure is advantageous, frontal, far side and rollover tests were performed. Current standard crash test dummies lack appropriate biofidelity when assessing sophisticated enhancements of standard safety restraints. Therefore the Thor dummy with a set of modifications from the BioSID were used in the tests. The results showed a considerable reduction of chest deflection in the frontal crash tests, head horizontal motion in the far side tests and head upward motion in the rollover tests. To conclude, an additional 2-point belt, in conjunction with, a 3-point belt and inboard torso side support offer a considerably increased protection in various crash situations without any negative consequences. For the covering abstract see ITRD E825082.

Design and Validation of the Neck for a Rear Impact Dummy (BioRID I)

To assess the protective performance of seats and head restraints, occupant models able to mimic the motion of a human in a crash are needed. Hence, a new mechanical dummy neck for low-velocity rear collision tests was developed. The dummy neck consists of seven cervical elements connected by pin joints. The stiffness properties of the neck were represented by rubber blocks mounted between each pair of vertebrae, as well as by muscle substitutes between the head and the first thoracic vertebra (T1). The muscle substitutes consist of cables connected to a unit containing springs and a damper. The neck was validated against volunteer test data ( j v of 7 km/h) and compared with the kinematics of the Hybrid III dummy. The new neck was tested as a part of a new dummy (BioRID) that produced a human-like motion of the T1. The kinematics of the new neck was within the corridor of the volunteers, during the major part of the first 250 ms of the crash event, for both displacement of the head relative to T1 and for the acceleration of the head. This applies to both duration and peak values. When compared with the new neck, the Hybrid III showed an earlier decrease of the horizontal acceleration of the head, less maximum horizontal displacement, and an earlier increase of the rearward angular displacement of the head relative to T1.