## 7 Conclusions  
This paper investigated the exploration route of a UAV to explore a disrupted road network, i.e., a road network after a disaster considering flying range limitations. The study is based on a conservative exploration strategy called back and forward. After each detected disruption, the UAV is redirected to the closest node connected to the functional road network detected so far. We proposed three refueling strategies to deal with the flying range limitation. The three refueling strategies were tested using a weight orientation criterion. This orientation criterion aims to find the combination of strategies that minimizes the duration of the exploration route to determine whether or not the given victim locations can be reached via the road network. The refueling strategies were proposed to extend the coverage of the UAV flying range. The algorithm was designed to save travel time by avoiding unnecessary network explorations. We assumed that a certain portion of victim locations can operate as refueling stations if they are connected by road to the DMC. This assumption is realistic as once a victim location is found to be reachable, it is certain that a functional path from the DMC to this victim location exists, and thus, the victim node can be resupplied with additional fuel (for the refueling station). The results show that the refueling strategy _MConservative_, where the refueling operation takes place when the flying capacity is lower than 50%, provides the best exploration routes for all instance clusters with a low disruption level. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Disaster Situation**} & \multicolumn{2}{c}{**Best Strategy**} \\ \hline
**Instance Size** & **Disruption Level** & **Number of Refueling Stations** & \(\textit{EConservative}\) & \(\textit{MConservative}\) & \(\textit{Conservative}\) \\ \hline \multirow{8}{*}{Small} & \multirow{2}{*}{low} & DMC & x & \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x & \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 50\% of victim locations & & x \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 100\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & 50\% of victim locations & x & \\ \cline{3-5}  & & \multicolumn{1}{c}{} & DMC & x \\ \cline{3-5}  & & \multicThe refueling strategy _Conservative_, where the refueling operation is performed only when the flying capacity is equal to or less than the buffer, provides the best solution for small and large instance clusters with a high level of disruption. The best strategy for all instances with a medium disruption level varies, depending on the number of refueling stations available, between _MConservative_ and _Conservative_. The most significant impact on total exploration time, apart from network size and disruption level, which cannot be influenced, had the fuel buffer and the number of reachable refueling stations.