###### Abstract  
This paper is dedicated to studying on-line routing decisions for exploring a disrupted road network in the context of humanitarian logistics using an unmanned aerial vehicle (UAV) with flying range limitations. The exploration aims to extract accurate information for assessing damage to infrastructure and road accessibility of victim locations in the aftermath of a disaster. We propose an algorithm to conduct routing decisions involving the aerial and road network simultaneously, assuming that no information about the state of the road network is available in the beginning. Our solution approach uses different strategies to deal with the detected disruptions and refueling decisions during the exploration process. The strategies differ mainly regarding where and when the UAV is refued. We analyze the interplay of the type and level of disruption of the network with the number of possible refueling stations and the refueling strategy chosen. The aim is to find the best combination of the number of refueling stations and refueling strategy for different settings of the network type and disruption level. disrupted road network; immediate response operations; on-line algorithm; refueling strategies; online exploration strategies; network cutting procedure; labeled network +
Footnote †: journal:  
0000-0001-9991-9999-22000-0001-9999-22000-0001-9999-22000-0001-9999-22000-0001-9999-22000-0001-9999-220000-0001-9999-220000-0001-9999-220000-0  
network and the aerial network of the affected area. Once a disaster occurs, some roads cannot be used because they have been affected by a natural, man-made, or technological hazard [5]. In current practice, organizations have been starting to include UAVs in response and reconstruction operations [6]. The use of UAVs promises cost efficiency for assessing destroyed road networks after a disaster. A UAV has a flying range that limits the number of affected zones that can be explored. Flying range limitations add a real risk of route failure because the UAV runs out of fuel mid-route [6; 7; 8; 9; 10]. UAV routing decisions in response operations are inefficient and do not meet the needs of humanitarian logistics due to uncertainty. As a result, several initiatives are aiming to develop tools to improve the reliability of on the fly routing decisions and to improve the efficiency of response operations [9]. The problem tackled in this paper is to assess the state of a post-disaster area using a UAV with flying range limitations. Based on the principle that most humanitarian relief operations are conducted using the road network, the main objective of our study is to determine the road network that is still functioning after a disaster. We consider that the only information available to start the exploration is the state of the road network in a pre-disaster situation and the location of the sites where victims are located. We refer to the road network in a pre-disaster situation as the known road network. The post-disaster road network is denoted as the disrupted network. We deal with uncertainty regarding the state of the road network by making routing decisions on the fly. The UAV starts at the Disaster Management Center (DMC); here, refueling is always possible. As the UAV advances its exploration, partial information regarding the state of the disrupted network is extracted, and new routing decisions are made. The UAV flies over the road network with a camera to transfer in real time a video to the DMC to determine if the explored edge is a functional or disrupted road. The objective of this exploration is to assess the road network state and evaluate the accessibility to the location of the victims, i.e., villages. The exploration is conducted with a UAV with a limited flying range due to the capacity of the fuel tank. During the exploration, functional roads and facilities detected determine the disrupted network. Refueling stations at the victim locations can be used to refuel the UAV and avoid a route failure.