## 4 Results
### Reliability Indicators  
The simulation results presented in the previous item show how important it is to take care of the correct condition of the suspension system. It may be helpful to know how the various reliability indicators, which are associated with prolonged driving in different, usually harsh environmental conditions, do change. Figures 19-21 present the results of the estimation of the reliability indicators for both cars analysed in this article. The shape of the probability function graph for the correct operation of the suspension system (Figure 19) for the car moving correctly and the one with a damaged suspension system follows a similar pattern. Clearly noticeable is the influence of car operating conditions on the correct operation of the suspension system. The whole range of factors related to road and environmental conditions make the various suspension system components gradually lose their performance characteristics over time, which translates into the reduced efficiency of the entire system. At this point, it should also be recalled that both driving skills and the load on the car also affect the appearance of the graph presented. The car moving correctly, i.e., the fully loaded one, achieves a fifty per cent probability of correct operation as early as at the mileage of 48,719 km. The car with the damaged suspension system, i.e., the one in which only the driver was present, reaches the same probability level only after it has travelled 54,156 km. The components most susceptible to damage, i.e., the rubber components in the suspension system, are mainly responsible for achieving such values. \begin{table}
\begin{tabular}{c c c} \hline
**Driving Speed** & **Kinetic Energy of the Vehicle with a** & **Kinetic Energy of a Car** \\
**(km/h)** & **Damaged Suspension System** & **Moving Correctly** \\ \hline
50 & 5.4 & 9.9 \\
70 & 8.0 & 15.1 \\
90 & 15.0 & 16.2 \\
120 & 17.4 & 27.0 \\
140 & 31.5 & 26.2 \\ \hline \end{tabular}
\end{table} 
Table 4: The value of kinetic energy as a function of the driving speed [k]. Figure 19: The probability distribution of the reliability of the car suspension system. Figure 20: The expected time of correct operation of the suspension system of a car with the damaged suspension system (**a**) and of the car moving correctly (**b**). According to the estimation of the indicators presented, the car moving correctly will reach the ten per cent probability of correct operation at 96,500 km, and the car with the damaged suspension will reach such probability at the mileage of 107,499 km. Exceeding these values may result in more frequent system failures and the need to replace the components, which will result in additional vehicle downtime. There is also an increased risk of unexpected system damage leading to a road incident. In order to ensure adequate travel safety, it is recommended that after that period, daily inspections should be extended to include additional suspension system maintenance or the replacement of defective components with new ones. The estimated value of the total unserviceability of the suspension system for both analysed cars will occur after more than 140,000 km. The above estimates are confirmed by the expected values of the system's correct service life as shown in Figure 20. Those expected values, too, indicate a fifty per cent system efficiency after 48,719 km for the fully loaded car and after 54,156 km for the car with the driver only. The shape parameter \(\alpha\) for both cars under analysis has a value above one; therefore the damage intensity function in each case will be an increasing function. This means that the probability of failure rate will increase over time [30]. This is confirmed by the suspension system damage intensity diagrams presented in Figure 21a. It follows from those that the run-in period for the system components of both cars will end after the mileage exceeds approximately 11,000 km.