## 4 Case Study: Application of APIRM Model at Istanbul Airport
### Risk Assessment of Hazards
\[\text{R}\left(\text{X}_{1},\text{X}_{2},\text{X}_{3}\right)=\text{L}\left(\text{ X}_{1},\text{X}_{2},\text{X}_{3}\right)\text{. F}\left(\text{X}_{1},\text{X}_{2},\text{X}_{3}\right)\text{. C}\left(\text{X}_{1},\text{X}_{2},\text{X}_{3}\right) \tag{1}\]  
The relationship between risk score and distress levels can be expressed as a linear equation with three independent variables, as shown in Formula (2). R is risk score (dependent variable). X\({}_{1}\), X\({}_{2}\), X\({}_{3}\) (FAA PASER, friction and IRI levels) are independent variables. \(\beta_{0}\) is the constant term, \(\beta_{1}\), \(\beta_{2}\), \(\beta_{3}\) are the independent variable coefficients that give the weights of distress levels affecting the risk score and \(\varepsilon\) is the error term. \[\text{R}=\beta_{0}+\beta_{1}.\text{X}_{1}+\beta_{2}.\text{X}_{2}+\beta_{3}. \text{X}_{3}+\varepsilon \tag{2}\]  
The likelihood scale is handled in seven levels between 0.1 (virtually impossible) and 10 (might well be excepted). Other levels consist of 'practically impossible = 0.2', 'conceivable but very unlikely = 0.5', 'only remotely possible = 1', 'unusual but possible = 3' and 'quite possible = 6'. [PERSON] and [PERSON], in the same study, also created a scale table for frequency values. The reference values in the frequency scale are between 10 and 1, as in the probability scale. In the frequency table, risks are classified according to their frequency of occurrence on a time basis such as hourly, daily, and annual. If the frequency of the risk is 'hourly', it is accepted that the risk occurs 'continuously' and the frequency value used in the formation of the risk value is the highest value of 10, and the probability of occurrence maybe once a year is the lowest value of 0.5. The other values are'very rare (a few per year) = 1', 'unusual (monthly) = 2', 'occasional (weekly) = 3' and 'frequently (daily) = 6'. In the calculation of the risk score, the cost and damage amounts resulting from the risk are taken into account in the scale table prepared for the third multiplier, possible consequence. The possible consequence scale table obtained as a result of this calculation is given in Table 5. In the scale created here, the scoring is undertaken by taking into account the cost or death rate that consequence will create [48]. Depending on the determined risk, likelihood, frequency and possible consequence values are obtained from the relevant tables and the risk score is determined by multiplying the three parameters. The obtained risk scores are classified according to Table 6. These are divided into five classes: acceptable risk, possible risk, substantial risk, high risk and very high risk. According to the calculated risk level, it is decided whether the risk will be accepted or not. Fifth-degree risks are very high risk and require immediate action. A fourth-degree risk is a high risk value and measures should be taken to reduce the risk in the short-term action plan. A third-degree risk is a significant risk, and the section should be monitored carefully. The pavement section facing a second-degree risk should be included in the action plan. A first degree risk is an acceptable risk and may not require immediate action. In sections where the risk is high, emergency action plans are prepared for maintenance and rehabilitation purposes [48]. \begin{table}
\begin{tabular}{l c} \hline \hline
**Possible Consequence** & **Value** \\ \hline Catastrophe (many fatalities, or \textgreater{}USD 10^{7} damage). & 100 \\ Disaster (few fatalities, or \textgreater{}USD 10^{6} damage) & 40 \\ Very serious (fatality, or \textgreater{}USD 10^{5} damage) & 15 \\ Serious (serious injury, or \textgreater{} USD 10^{4} damage) & 7 \\ Important (disability, or \textgreater{}USD 10^{3} damage) & 3 \\ Noticeable (minor first aid accident, or \textgreater{}USD 100 damage) & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Fine–Kinney possible consequence scale [48].