## 4 Results and Discussion  
Table 3 summarizes cost-based studies employing machine learning tools like ANN, Bayesian Networks, and Genetic Algorithms, as well as other analytical tools, for the cost prediction of OCCM and CIPPRT renewal methods. Some of the relevant studies are briefly described in the paragraphs below. [PERSON] et al. [74] focused on traffic delay costs and found that trenchless technologies eliminate traffic disruptions, making them a more economical option than OCCM. Trendless methods can be up to 75% cheaper than OCCM, particularly for smaller-diameter pipes and in urban environments [60]. Trenchless methods generate 97% less greenhouse gas emissions compared to OCCM. Open-cut methods incur social costs ranging from 6% to 78% of direct project costs, depending on location and population density. Trenchless methods have much lower social costs, estimated at only 3% of project costs. Open-cut methods disturb 53 times more physical material than trenchless technologies, leading to significantly higher ecological disruption. Hence, it can be concluded that trenchless technologies are often more cost-effective and environmentally sustainable, especially in high-density urban settings; the inclusion of social costs and environmental impacts in project evaluations is essential for making informed decisions. [PERSON] et al. [75] compared the overall project costs of trenchless technologies with those of OCCM. It concluded that trenchless technologies offer comparable surface restoration costs, are effective in urban areas, and result in fewer maintenance and rehabilitation expenses. Open-cut methods, however, reduce pavement lifespan by about 30% and increase maintenance costs significantly (from 85 CAD/m\({}^{2}\) to 146 CAD/m\({}^{2}\)). [PERSON] et al. [20] studied the costs of traffic disruption caused by utility construction using OCCM and trenchless methods. The study revealed that trenchless methods minimize traffic disruption costs, which ranged between $0 to $126, compared to $297 to $156 for OCCM. [PERSON] et al. [76] found that OCCM using shoring or shielding costs $442.90 per linear foot (LF), significantly higher than the $168.35 per LF cost of pipe bursting. Open-cut costs varied based on the type of excavation wall protection used. In 2006, [PERSON] [77] created a Stochastic Life-Cycle Cost (SLCC) framework employing Monte Carlo simulations to analyze and predict cost variations over a system's lifespan. He evaluated and optimized water main repair, renovation, and replacement methods. The software @Risk 4.5 was used to run the Monte Carlo simulations, which were integrated into the SLCC framework to handle probabilistic inputs. It confirmed that the open trench repair, slip-lining renovation, and pipe bursting replacement (for small diameters) are the most cost-effective approaches, and that the effective application of the SLCC model can significantly reduce the estimated $15 billion cost associated with water main replacement and rehabilitation in Canada. OCCM is the most effective method for replacing water mains with larger diameters (greater than 30 inches).  
[PERSON] [24] conducted a cost comparison for sewer pipeline replacement in Troy, Michigan, revealing that the pipe-bursting method saved $104 million, compared to OCCM. [PERSON] et al. [78] noted that the cost evaluation in their study incorporates both direct costs (pre-construction, construction, and post-construction) and social costs (e.g., disruptions for pedestrians and vehicles, and cleaning expenses). Using the Analytical Hierarchy Process (AHP), these costs are integrated into a multi-criterion decision-making framework that also considers duration and environmental impact. Decision-makers assign weights to these criteria (e.g., 70% for cost) and calculate a composite score for each rehabilitation method. AHP enables systematic comparison by combining weighted scores, helping to identify the most suitable method based on overall utility.