# UAV-Assisted Hybrid Scheme for Urban Road Safety Based on VANETs
## 1 Introduction  
Vehicular ad hoc networks (VANETs) is an application of mobile ad hoc networks (MANETs) for the field of the internet of vehicles (IoV) [1; 2]. Compared with other mobile ad hoc networks, VANET is a network that can communicate wirelessly among the vehicles, and between the roadside units (RSUs) to vehicles [3]. Intelligent Transportation System (ITS) applications are being supported by VANETs. It is designed for the comfort and safety of the passengers and also to improve the transportation efficiency [4]. For the new application scenarios, inter-vehicle communication (IVC) has aroused widespread research interest in academia as well as industry [5]. The vehicles are treated as autonomous mobile nodes, connected in an environment wirelessly, though these nodes are not present in similar range, passing through multiple intermediate nodes [6]. The VANETs build and maintain ad hoc networks with the aid of routing protocols [7]. The routing protocol proposed in VANETs may be table-driven (proactive), on-demand-driven (reactive), or hybrid [8; 9]. The on-demand (reactive) routing protocols discussed here are ad hoc on-demand distance vector (AODV) and our proposed unmanned aerial vehicle (UAV)-assisted AODV (UAVa). For mobile ad hoc networks a routing isimportant [10]. A lot of work has been conducted into routing protocols [11]. Many protocols are aimed at delivering higher quality of service (QoS) and saving more resources [12]. AODV is the most popular routing protocol which contains the technique of route discovery and route maintenance [13]. The source node transmits the packet of the routing requests to the network destination node. After the routing request packet has been received, the intermediate node must forward the packet before the routing request is received by the destination node, and the repeat request packet is discarded [14]. The AODV routing protocol also attaches the sequence number to the request packet to control the routing loops at the same time. Without any transmission requirements, the proactive routing protocol can create routes between nodes in advance. This is different from the reactive routing protocol, i.e., a node only updates its neighbors so far with its known routing information, assuming that all nodes will use the whole network updated to the information [15]. Private vehicles have become an integral part of our everyday lives because of the rapid growth of our society, the rise in individual vehicles; traffic congestion has become an acute issue that needs to be addressed [16]. In our proposed scheme, congestion control is our first target. Nowadays, congestion regulation has become a widely debated concern in vehicle-to-vehicle (V2V) communications, i.e., ensuring secure and effective communications through the use of limited resources available in vehicular ad hoc networks (VANETs) [17]. A node in VANET represents the vehicle. The shortcomings of existing congestion control mechanisms over VANETs have inspired us to propose an approach with an improvement in the existing algorithms to meet the demands of current technology in handling vehicles in addition to assuring safety in communicating vehicles with reliability. The issues faced before introducing the solutions to the congestion in VANETs were limited bandwidth, high mobility, retention of connection amongst the moving nodes, avoidance of interference and noise, maintaining signal strength in the presence of the dense building on the sides of the roads, etc. [18]. In this article, an innovative mechanism is proposed in which current-time traffic information accumulation and sharing to the entire traffic network and how to regulate congestions before it happens are studied. This not only ensures the sharing efficiency but also demonstrates the low complexity of accumulating the current-time traffic information and sharing it. Within the existing conditions of traffic, the traffic rules were completely used to remove any congestion.