## 4 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Year** & **Authors** & **Focus Area** & **CC** & **EC** & **SC** & **LCCA** & \multicolumn{2}{c}{**Overall Findings/Tools**} \\ \hline
2007 & [PERSON] and [PERSON] [57] & Social costs; Environmental impact & ✗ & ✗ & ✗ & - & \
\begin{tabular}{c} - \\ \end{tabular} &
\begin{tabular}{c} Trenchless technologies reduce social costs by 50–60\% \\ - \\ Reduced total project costs by \\ \end{tabular} \\ \hline
2008 & [PERSON] [24] & Open-cut and Pipe bursting & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Cost of the pipe bursting method was \\ 5104,269,826 less than the OCPI \\ \end{tabular} \\ \hline
2008 & [PERSON] et al. [92] & Traffic delays & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} TT scores 25\% higher in bid \\ cost-effectiveness by incorporating \\ social costs \\ \end{tabular} \\ \hline
2009 & [PERSON] et al. [78] & Water networks & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} TT reduces costs by 40\% and duration \\ by 30\% in water network projects \\ \end{tabular} \\ \hline
2009 & [PERSON] [51] & Indirect costs; traffic delays & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} TT reduced external costs from 25\% to \\ 10\% of total project costs, \\ saving \$400,000 \\ \end{tabular} \\ \hline
2010 & Matthews and Allouche [81] & Traffic delays; safety risks; business disruptions & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Social costs constitute up to 30\% of \\ project costs \\ - \\ lost tradeoff delays \\ \end{tabular} \\ \hline
2010 & [PERSON] [93] & OCPI (Noise pollution) & ✗ & ✗ & ✗ & ✗ & \
\begin{tabular}{c} - \\ \end{tabular} &
\begin{tabular}{c} Noise levels exceeding 87.49 dB incur \\ an average 28.57\% productivity loss, \\ increasing project duration and \\ fuel usage \\ \end{tabular} \\ \hline
2011 & [PERSON] [94] & \
\begin{tabular}{c} OCPI and TT \\ (Dust generation) \\ \end{tabular} & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} The economics behind the loss of \\ productivity due to an increase in \\ dust generation \\ \end{tabular} \\ \hline
2011 & [PERSON] et al. [79] & Open-cut and CIPPRT & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Open-cut and CIPPRT renewal costs \\ were \$750/LF and \$325/LF, \\ respectively \\ \end{tabular} \\ \hline
2012 & [PERSON] [1] & \
\begin{tabular}{c} Empirical \\ calculations and emission \\ factors \\ \end{tabular} & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} PB reduces CO\({}_{2}\) emissions by 72.6\% \\ compared to OCPI. \\ \end{tabular} \\ \hline
2013 & [PERSON] [80] & OCPI & ✗ & ✗ & ✗ & - & Annual total costs = \$511.22/lane \\ \hline
2013 & [PERSON] and [PERSON] [95] & LCC estimation for \\  & and [PERSON] & construction & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} ANN achieved an average error of 1\% \\ for the Excel Solver approach and 2\% \\ for backpropagation \\ \end{tabular} \\ \hline
2013 & [PERSON] & Environmental impact; surface & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Trenchless methods lower total costs \\ by 25\% and improve sustainability \\ index scores \\ \end{tabular} \\ \hline
2015 & [PERSON] et al. [82] & CIPPRT & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} C-footprint for CIPPRT method \\ through NASTT, E-Calc, and NASTT \\ BC were 3.11, 2.90, and 2.66 tonnes, \\ respectively \\ \end{tabular} \\ \hline
2015 & [PERSON] et al. [61] & OCPI & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Social costs = \$400/LF and \$460/LF, \\ respectively, for two case studies \\ \end{tabular} \\ \hline
2015 & [PERSON] et al. [81] & Traffic delays; environmental degradation & ✗ & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Trenchless methods reduce traffic \\ delay costs by up to 50\%, saving \\ \$10,000 to \$45,000 per project \\ \end{tabular} \\ \hline
2016 & [PERSON] et al. [84] & OCPI (Carbon footprint) & ✗ & ✗ & ✗ & - &
\begin{tabular}{c} Steel pipe CO\({}_{2}\) emissions were 36\% \\ greater than for PCCP \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._