Clustering is a promising technique to manage network resources efficiently and, in vehicular communications it is used to group vehicles with similar characteristics managed by a selected vehicle called a Cluster Head (CH). Due to the highly dynamic topology in vehicular networks, a CH selection process becomes a challenging task. Thus, this paper presents a new clustering scheme, namely, Efficient Cluster Head Selection (ECHS) scheme to select the most suitable CHs. The proposed ECHS scheme introduces important conditions pertaining to the methods deployed in constructing clusters before starting the CH selection. For instance, based on the ECHS rules the ideal CH is the one that centralizes the cluster. This is because it will remain connected as long as possible with its neighbors. The ECHS scheme also guarantees proper clustering distribution in the network, so that the distance between two consecutive clusters are adjusted carefully. Such conditions are guaranteed to effectively cluster vehicles in the road and make the ECHS scheme works better than its counterpart. Simulation experiments are conducted to examine the performance of the ECHS and the results demonstrate that the ECHS scheme achieves the design objectives in terms of CH lifetime, Cluster Member Lifetime (CML), Packet Loss Ratio(PLR), Overhead for Clustering(OC), Average Packet Delay (APD), and Cluster Number (CN). INDEX TERMS Clustering, Cluster Head, Cluster Gateway Candidate, Vehicular Ad hoc Networks. I. INTRODUCTION Nowadays, shortcomings of the traditional transportation systems are eliminated significantly by employing intelligent Vehicular Ad hoc Networks (VANETs). Due to the rapid development of wireless sensors and Internet of Vehicles (IoVs) [1], VANETs can be integrated with other technologies such as Cloud and Fog computing [2][3][4]. This sort of integration makes VANETs easy to deploy and include more traffic management applications. Basically, communication in VANETs can be divided into two categories, depending on the types of the running applications and requested services. The first one, is Vehicleto-Vehicle (V2V) communication, which is commonly used when vehicles share local traffic information among each other without using infrastructure configuration [5][6][7]. The second one is Vehicle-to-Everything (V2X) communication which combines any type of communication between vehicles and infrastructure nodes such as a RoadSide Unit (RSU), a Fog Node, a Base Station, and a Cloud Center. (V2X) communication usually helps vehicle to collect information about different zones inside a city to deduct traffic congestions and to discover free-congested

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In intelligent transportation systems, broadcasting Warning Messages (WMs) by Vehicular Ad hoc Networks (VANETs) communication is a significant task. Designing efficient dissemination schemes for fast and reliable delivery of WMs is still an open research question. In this paper, we propose a novel messaging scheme, Advanced Speed and Density Warning Message (ASDWM). ASDWM is a broadcast-based scheme that meets design objectives and achieves high saved rebroadcast and reachability, as well as low end-to-end latency of WM delivery. The ASDWM uses vehicle speeds and vehicles density degrees to help emergency vehicles to send WM according to a road condition, adaptively. Simulation results demonstrate the effectiveness and superiority of the ASDWM over its counterparts.

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