**3. Results**

The results for the first and second stage, which covers the frontal impact of the whole car and subsidence, are presented in [28]. This study will only present the results for stage three.

During all analysed cases, characteristic time moments presented in Figure 6 can be distinguished. The subsidence stage ended at time t = 0.3 s and this is also the beginning of the analysis of the third stage. After approx. 10 ms, the airbag and belt pretensioner were activated. At t = 0.316 s the initial airbag opening is visible. After 36.0 ms, the airbag is close to full inflation, which pushes the upper limbs out of the steering wheel or handles. After 56.0 ms, the dummy's head encounters the airbag. At t = 0.380 s, the head reaches the maximum forward tilt, followed by the driver's rebound and a rearward movement to the seat. The contact between the driver's head and the airbag lasts until the time t = 0.400 s. At a time of approx. t = 0.432 s, the dummy hits the seat's backrest. This impact is asymmetrical to the seat.

**Figure 6.** Characteristic time points of the simulations.

The maximum longitudinal displacement of the conventional centre of gravity of the dummy (i.e., corresponding to the centre of mass without amputation) is achieved at different times in each case (Figure 7). It is worth noting that at this moment, depending on the equipment used, the position of the dummy differs. In the RD case, the forearms and arms are pushed outwards while keeping the hands within the steering wheel. Knees hit the elements of the space under the steering wheel. In cases H, the left hand is pushed completely out of the steering wheel and the right hand hits the lower part of the central console. In cases C, the right hand strikes higher and in a different position. In cases H and C, the number of zones of contact between the dummy and the vehicle interior depends on the disability under consideration.

**Figure 7.** Positions of the dummy at the moments corresponding to the maximum longitudinal displacement.

The type of equipment used significantly affects the lateral displacements of the driver's conventional centre of gravity. In the RD case, the maximum displacement was about 10 mm and, importantly, in the final stage of impact the pelvis almost returned to its initial position (Figure 8). In the HB and CB cases, there is no return to the initial position and much greater maximum lateral displacement when the dummy hits the seat (approx. 15.5 mm and 18.0 mm respectively).

**Figure 8.** Lateral displacement of dummy H-point.

Analysing the H group, it can be seen that at the moment of the maximum longitudinal displacement of the dummy's centre of gravity in relation to the seat, the maximum lateral displacement occurs for HLL (Figure 9). In turn, when the dummy hits the seat's backrest, the maximum lateral displacement is for HRH (about 29 mm).

**Figure 9.** Lateral displacement of dummy H-point.

In group C the greatest lateral displacement can be observed for CLL, CRL and CBL cases (Figure 10).

**Figure 10.** Lateral displacement of dummy H-point.

Lateral movements go with shoulder rotation. When analysing the influence of the equipment used for DP (Figure 11), there is no significant change. At the initial impact phase, in all cases, the right shoulder extends forwards more and, after rebounding from the airbag, the arms start to rotate in the opposite direction.

**Figure 11.** Angle of rotation of the shoulders.

Analysing group H, one can see the same type of changes, but with different levels of them (Figure 12). The highest rotation in the first impact phase is for HB and HRL cases (about 9◦). In the second phase, for HLL and HRH (above 10◦).

**Figure 12.** Angle of rotation of the shoulders.

Similarly, for group C (Figure 13). In the first phase, the highest rotation is for CB and CRL (about 7.5◦) and in the second phase for CLL (over 12◦) and CBL (over 15◦).

**Figure 13.** Angle of rotation of the shoulders.

The work also analysed the course of change of forces between the dummy and seat belts. In cases where the dummy had all the limbs, no significant changes between the individual runs are visible (Figure 14). The highest peak of strength occurs immediately before the head of the dummy (and thus part of the chest) contacts the airbag. After that time, the value drops by about 2 kN and is maintained until the maximum longitudinal displacement of the dummy in relation to the chair is reached.

**Figure 14.** Comparison of contact force between the seat belts and the dummy.

A similar character of the course of force between the belts and the dummy can be observed for analyses from group H (Figure 15). Only in the HLL there is no decrease in force, it remains at a constant level until the time when the maximum movement of the longitudinal dummy in relation to the seat is reached.

**Figure 15.** Comparison of contact force between the seat belts and the dummy.

In group C (Figure 16), no loss of strength after the dummy starts to contact the airbag is visible in two cases—CBL and CLL.

**Figure 16.** Comparison of contact force between the seat belts and the dummy.

The use of additional equipment for the DP, in addition to influencing lateral displacement, shoulder rotation and the course of force between the belts and the dummy, also affects skull injuries expressed as HIC (Head Injury Criterion) (Figure 17). Compared to RD, HB and CB have at least 6% lower HIC15 and 7% lower HIC36 values.

**Figure 17.** Head Injury Criterion (HIC) comparison.

In the H group (Figure 18), different HIC15 and HIC36 values were obtained for individual cases, but no significant differences were observed. The maximum reaches respectively 4% and 3%.

In group C (Figure 19) for HIC15 the difference between the maximum and minimum result is about 4%. For HIC36 the difference increases less than 6%. The smallest value was obtained for CLL and the largest for CB.

**Figure 19.** Head Injury Criterion (HIC) comparison.
