## 5 Conclusions
### Cost Analysis and Machine Learning Integration in Pipeline Rehabilitation  
The comparative life-cycle cost analysis for Open-Cut Construction Method (OCCM) and CIPPRT reveals critical insights into the economic, environmental, and social impacts of these two pipeline rehabilitation approaches. OCCM, being a traditional method, remains effective in rural or non-pavement areas where disruptions are minimal. However, its high environmental and social costs, including extensive excavation and emissions, often outweigh its advantages in urban or high-traffic settings. CIPPRT, on the other hand, demonstrates superior adaptability and efficiency, particularly in urban environments with high utility congestion. Its minimal excavation requirements, reduced greenhouse gas emissions, and lower social costs make it a sustainable and economically viable alternative for most rehabilitation projects. Despite its higher initial investment and dependency  
Figure 10: Keyword co-occurrences in VOSviewer. on specialized equipment, the long-term savings and reduced environmental footprint position CIPPRT as a preferred choice for modern infrastructure projects. The pie chart below visualizes the distribution of costs associated with the LCCA of sanitary sewer rehabilitation methods, highlighting four key categories: Social Costs (SC), Environmental Costs (EC), Construction Costs (CC), and LCCA (Figure 11). Based on Table 4, Social Costs constitute the highest share, at 38.8%, reflecting significant disruptions like traffic delays, business losses, and other societal impacts caused by traditional methods such as OCCM. Environmental Costs account for 30.6%, underscoring the emissions and resource use involved in materials production and the extensive excavation associated with OCCM. Construction Costs, comprising 28.6%, illustrate the direct costs of labor, equipment, and materials needed for these projects. Meanwhile, Life-Cycle Costs contribute the smallest portion (2%) but represent critical factors in long-term project sustainability, including maintenance and rehabilitation. This distribution underscores the need for adopting trenchless technologies such as CIPPRT, which can significantly reduce social and environmental costs, as shown in the studies comparing the two methods. These findings advocate for the incorporation of all cost categories within the LCCA to make more sustainable decisions with respect to pipeline rehabilitation projects. The integration of ML tools and methodologies, such as Monte Carlo simulations and the Analytical Hierarchy Process, further enhances the accuracy and reliability of LCCA. These tools enable decision-makers to evaluate complex cost factors, including social disruptions, environmental impacts, and long-term maintenance, to choose the most suitable rehabilitation method. The study underscores the importance of including social and environmental costs in the LCCA to make informed decisions that align with sustainability goals. The findings emphasize that while OCCM may be viable in select scenarios, trenchless technologies like CIPPRT provide a more sustainable, efficient, and cost-effective approach for pipeline rehabilitation, especially in urban settings. The following pie chart shows that Random Forest and ANN are the tools most frequently used for the cost estimation (Figure 12). The following section, Table 4, includes the most relevant studies that are based on Machine learning and deal with cost prediction. Figure 11: Distribution of papers based on the different costs.