## 3 Materials and Methods
### Simulation of a Road Incident  
Unexpected damage to the suspension system components may result in unexpected situations on the road. Given small speeds and insignificant damage, the driver is able to react in sufficient time and stop the vehicle. This is not, however, always possible, and dangerous situations may at times occur on the road. One such situation involves the lack of control over the car when the suspension system is damaged and the car moves to the opposite lane. In this article, precisely such a situation will be simulated.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **Unit** & **Front Axle** & **Rear Axle** \\ \hline Frequency of vibrations of the suspended mass & Hz & 1.16 & 1.33 \\ Design suspension deflection & mm & 155 & 116 \\ Elasticity coefficient & kN/m & 22.4 & 23.5 \\ Stabiliser bar stiffness & kN/m & 11.2 & 11.7 \\ Nominal pressure & kN & 3.74 & 2.71 \\ Progression of stiffness & - & 0.5 & 0.5 \\ Wheel torsional flexibility & \% & 15 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The basic parameters of the suspension system.  
Various traffic conditions are assumed in the simulation. First of all, traffic was simulated in a built-up area, where vehicles travelled at 50 km/h. Figure 6 shows an example of a built-up area where a road incident occurred.  
Next, traffic was simulated in a built-up area, with vehicles moving at a higher speed, that is, 70 km/h.  
Finally, traffic was simulated in an undeveloped area, where cars are allowed to travel at a maximum speed of 90 km/h, as well as on an expressway and a highway, each time assuming the maximum speed allowed.  
Each time, one of the cars runs over a 0.10 m high oblong obstacle lying across the roadway. At that point, damage to the suspension system occurs, and the left front wheel breaks off. In the case of urban traffic, the obstacle may be a deceleration threshold; in other cases, it is an unspecified item. Before damage to the suspension system, that vehicle covered many kilometres on roads whose technical condition resembles the conditions shown in Figures 2 and 3.  
Damage to the suspension system upon hitting an obstacle is the result of the accumulation of previously occurring adverse phenomena, which caused its gradual destruction. The obstacle appearing in the simulation led to exceeding the permissible stresses in the system and, as a consequence, fatigue wear of its components.  
After running over the obstacle and damaging the suspension system, the driver lost control of the car, which began to move to the opposite lane. There was no investigation into which component was damaged and what the exact cause of damage was. At the same time, from the opposite direction, another car was coming, which was moving according to traffic regulations or was motionless on the road shoulder (depending on the simulation option). In addition, in urban traffic, pedestrians were walking along road shoulders. A road accident takes place with various consequences, depending on the vehicle's speed. This article includes simulation results for two sample scenarios. The first one assumed that both cars were travelling at 50 km/h. In the second, the speed of the cars was assumed to be 70 km/h. The cars were at such a distance from each other before the accident that a head-on collision was caused.