# A Proactive Approach to Extended Vehicle Routing Problem with Drones (EVRPD)
## 2 Vehicle Routing Problem with Drones-Literature Review  
The current frequent and varied use of drones in logistics, agriculture, security, inspection, etc., results in the need to properly plan their use for the implementation of specific operations. For example, if the drone needs to visit several locations, this can be modeled as a traveling salesman problem (TSP) [12, 13]. This one is quite common in the infrastructure industry, where the drone must check selected points of the building; for example, in agriculture, the drone must collect information on field sampling points, or in the emergency industry, the drone delivers blood to several hospitals, and in logistics, the drone delivers to customers in the last mile. An overview of the possibilities of using drones to carry out various operations is presented in [14]. There has been a certain classification of operations that could be carried out with the help of drones. The most important of them are:  
1. Area coverage where sensor or camera drones should monitor (cover) an area that may take various shapes. This problem occurs in disaster management (assessment of the damage after an earthquake, flood, tornado, etc. ), agriculture (observing vegetation indexes and creating digital maps of the crop area), aerial archeology, etc. [15]
2. Search operations where drones need to find a stationary or moving object. In a drone search, this problem is easily observed in wildlife monitoring and search and rescue applications. You need to define a search path for one or more drones to find an object in an unknown location. 3. Routing for a set of locations where drones must visit a specific and finite set of addresses. In many surveillance and delivery applications, drones must tour a certain set of locations starting and ending at the depot. The resulting planning problems can be modeled as generalized versions of one of the underlying routing problems, such as a TSP [16; 17], multiple TSPs [18; 19; 20; 21; 22; 23; 24; 25], or a VRP [26; 27; 28; 29; 30]. 4. Data collection and charging on wireless sensor networks (WSNs) where drones must collect information from a specific or given set of locations while considering the communication schedule and limited memory capacity. 5. Allocating communication links and computing power to mobile devices with set (or redirected) drones to provide communication links with mobile devices of sufficient quality. All the above-mentioned and other applications of drones have a certain weakness: the fact that they can only spend a very limited time in the air. This results in a significant reduction in the range of operations carried out by drones. Therefore, drones have become frequently used in conjunction with other robots and means of transportation (generally vehicles), leading to increased efficiency and effectiveness in carrying out their operations. The problem discussed in this article concerns operations that are carried out jointly by vehicles and drones. In the literature describing the performance of combined operations by drones and vehicles, they are mostly concerned with the mapping of routes for a set of locations (c) as used in logistics [31]. Very interesting work in this area was presented in [32; 33]. Routing operations can also take place in precarious or dynamic environments, such as monitoring disaster regions or suppressing fires [34; 35; 36]. Such problems were classified as a VRPD (vehicle routing problem with drones) [7; 37; 38]. To a lesser extent, the use of drones concerns other operations, such as the coverage of an area (a) [39; 40] or extension of ground vehicle connectivity [41; 42; 43; 44]. Soon, drones may potentially be supported by ships in search operations (b) [45] and in collecting data from sensors monitoring underwater pipes (d). In the VRPD, a fleet of vehicles equipped with drones delivers shipments to customers.