## 3 Results and Discussion
### Establishment of Criteria for Condition Assessment  
The most important results of the test campaign so far include the following:  
* Deflectometric ranges increased across the study area, which required the definition of characteristic values through a distribution fitting analysis (characteristic D\({}_{0}\) = 145 \(\upmu\)m and characteristic D\({}_{1800}\) = 13 \(\upmu\)m). * The assessment of durability did not yield significant anomalies. Despite some high ISM values at individual slab corners, these are not directly loaded, implying that the durability assessment is less critical for the present case. * The LTE was satisfactory for the joints but showed a greater range for the cracks. Cracks with larger opening widths showed the lowest LTE values. The deflection indicators for the slabs with cracks were also of a higher order of magnitude than for the majority of the slabs. Therefore, it was assumed that the deflectometric assessment exceeded the LTE assessment. Based on these results, there was a need to define thresholds (or control values) for both deflectometric indicators (i.e., D\({}_{0}\) and D\({}_{1800}\)) to strategically manage the pavements  
Figure 11: Load transfer efficiency for joints and cracks. under study. Based on the authors' experience with deflectometric assessment of concrete pavements [15] and engineering judgment, it was decided to increase the characteristic values by 50% to define values beyond which the slabs should be considered ad hoc for possible rehabilitation planning. For this purpose, threshold values of D\({}_{0}\) = 220 \(\upmu\)m and D\({}_{1800}\) = 20 \(\upmu\)m were defined. To further verify the choice of these values, response calculations were performed for the design cross-section shown in Figure 2 using the in situ FWD load. Linear elastic behavior was assumed for all layers [30]. A maximum central deflection of 194 \(\upmu\)m was determined, which is close to the limit value of 220 \(\upmu\)m. To avoid being too conservative, a value of 220 \(\upmu\)m was determined to be more suitable for slabs with a significant degree of damage. Taking the above into account, three levels were defined to map the entire area. Since the purpose of this study was to develop a general framework for decision making, a color was assigned to each level to indicate the severity of a slab's condition based on deflectometric assessment, LTE measures, and durability assessment, as shown in Figure 12. Orange indicates \"Investigation for major rehabilitation, including slab replacement, etc.\"; yellow indicates \"Investigation for minor rehabilitation, including local repairs, joint restoration, crack sealing or resealing, etc.\"; and green indicates \"Do nothing.\"  
Of course, the final decision on what action to take should be made considering technoeconomic feasibility and the strategic priorities of the road owner. This means that even if individual slabs are assigned to the orange level, slab replacement in full lane still needs to be considered as an alternative, as in the former case, the anticipated service life of  
Figure 12: Framework for individual slab condition assessment. the restored slabs may be less than ten years [5]. In other words, slab replacement in a full lane could be a more rational preservation approach, as it limits the possibility that many surrounding undamaged slabs will reach failure potential earlier than initially expected because of the reconstruction procedure of individual slabs. An illustration of this concept is provided in Figure 13.  
It should be noted that the way in which characteristic values and thresholds are defined is not unique and depends on the case-specific conditions on site, especially if there are no previous monitoring records for the pavement under investigation. In any case, the results of the visual inspection may trigger additional random deflectometric measurements and complement the interpretation of the deflectometric data.