I. Introduction
Vehicular ad-hoc networks (VANETs) have emerged in recent years as a solution to enhance the way we travel and communicate on the roads, and to regulate vehicular traffic. In these networks, vehicles are seen as mobile nodes that communicate with each other, either directly via on-board devices in ad-hoc fashion or in centralized fashion via road side units (RSUs) that are deployed along the road. This latter type of communication is commonly referred to as V2I (Vehicle to infrastructure).