## 3 Methodology
### Condition Evaluation of Airport Pavement Performance in APMS  
The identification of distresses (hazards) in airport pavements involves periodic monitoring and evaluation, beginning with defining the pavement network. This network comprises runways, taxiways, and aprons as distinct branches within an airport, with run  
Figure 1: APIRM model implementation methodology. ways further segmented into sections like touchdown zones (TDZs) and a middle section. Taxiways and apron pavements are treated as single sections, and each section is divided into smaller sample units to ensure comprehensive assessment coverage. Functional and structural methods are used to evaluate these networks. Functional assessments examine parameters like surface irregularities, friction for braking safety, and overall surface deterioration, while structural assessments focus on pavement strength to support vehicular traffic [29]. Functional assessment methods include the Pavement Condition Index (PCI), outlined in ASTM D5340 and utilized in the PAVER system by the U.S. Army Civil Engineering Research Laboratory [30]. PCI visually assesses surface deterioration, scoring pavements from 0 (unusable) to 100 (excellent). Another method is the FAA's Airfield Pavement Surface Evaluation Rating Scale (PASER), documented in AC 150/5320-17 and developed with the University of Wisconsin--Madison [31]. This method is summarized in Figure 2, detailing the condition ratings and descriptions. PASER rates pavement conditions on a scale from 5 (excellent) to 1 (failed), with the rate of degradation influenced by factors such as original construction quality, environmental conditions, and traffic volume [32]. Pavement roughness, a key factor in an airport pavement management system (APMS), refers to surface irregularities that affect aircraft safety, induce fatigue, and impact passenger comfort due to cockpit vibrations and vertical acceleration. Two methods are commonly used to measure roughness: the Boeing Bump Index (BBI), described in FAA Advisory Circular AC 150/5380-9 (2009), which evaluates isolated bumps encountered at speeds of 240-370 km/h using a virtual straight edge [33] and pavement profile measurement, which collects elevation data processed through digital filtering to calculate metrics like quarter-car simulation (QCS), root mean square vertical acceleration (RMSVA), and slope variance (SV) [34]. The International Roughness Index (IRI), derived from QCS and standardized through the International Road Roughness Experiment (IRRE) in Brazil in 1982. provides recommended thresholds for airport pavement roughness outlined in Table 1[30; 35]. The braking performance on runway pavements is critical for aviation safety, especially with modern turbojet aircraft, which are heavier and faster. Wet conditions significantly reduce tire-pavement friction, increasing the risks of aquaplaning and skidding. Areas like the touchdown zones (TDZs) are particularly vulnerable due to frequent landings, which lead to tire contaminant buildup, reducing braking efficiency. Regular cleaning of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Level** & **State** & **IRI (m/km) Runway** & **IRI (m/km) Taxiway** \\ \hline
4 & Regular & 2.00 & \(\approx\)0.10 \\ \hline
3 & Acceptable & 2.00 \(<\) IRI \(\leq\) 2.50 & 3.00 \(<\) IRI \(\leq\) 3.40 \\
2 & Pre-critical & 2.50 \(<\) IRI \(\leq\) 3.00 & 3.40 \(<\) IRI \(\leq\) 3.80 \\
1 & Critical & - IRI \(\leq\) 3.00 & - IRI \(\leq\) 3.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: IRI roughness scale for airport pavements. Figure 2: FAA PASER rating scale. these contaminants and ensuring proper drainage are essential to maintain safe braking performance and to prevent water accumulation. Additionally, runway surfaces deteriorate over time due to continuous braking and wheel rotation, necessitating periodic friction measurements, particularly during heavy traffic or adverse weather conditions like precipitation.