Vehicular ad hoc networks (VANETs) have recently been proposed as one of the promising ad hoc networking techniques that can provide both drivers and passengers with a safe and enjoyable driving experience. VANETs can be used for many applications with vehicle-to-vehicle (V2V) and vehicle-toinfrastructure (V2I) communications. In the United States, motor vehicle traffic crashes are the leading cause of death for all motorists between two and thirty-four years of age. In 2009, the National Highway Traffic Safety Administration (NHTSA) reported that 33,808 people were killed in motor vehicle traffic crashes. The US Department of Transportation (US-DOT) estimates that over half of all congestion events are caused by highway incidents rather than by rush-hour traffic in big cities. The US-DOT also notes that in a single year, congested highways due to traffic incidents cost over $75 billion in lost worker productivity and over 8.4 billion gallons of fuel. Some of the significant applications of VANETs are road safety applications including collision and other safety warning systems, driver convenience and information systems, and, in the future, intelligent traffic management systems.This special issue on VANETs presents current groundbreaking research, projects, and standardization efforts that have been done in the area of vehicular communications. In both the review process, and the production process we have aimed for the highest possible quality and speed. Papers in this special issue have been rigorously peer-reviewed. With an internationally acclaimed Editorial Board, we have selected some high-quality research work in the field of VANETs. Critical reviews were received from S. Olariu, G. Yan, S. El-Tawab (Old Dominion University, USA), C. M. Pinotti (University of Perugia, Italy), S. Salleh (University of Technology, Malaysia), M. E. Rizvi and S. Zehra (Norfolk State University, USA), Z. Zaidi (NICTA, Australia), and X. Chen (University of Oklahoma, USA).In "Spectrum sensing for cognitive vehicular networks over composite fading," the authors consider shared utilization of the radio spectrum via cognitive radio systems to increase spectrum efficiency and quality of vehicular services. A cognitive radio system is a mechanism which allows unlicensed cognitive users (CUs) to utilize idle unused bands. Spectrum sensing is the first step that should be carried out before permitting cognitive clients to approach an authorized channel. A viable choice for spectrum sensing due to its simplicity, low computational cost, and ability to be applied on any kind of deterministic signal is energy detection (ED). However, hidden terminal and low SNR problems due to shadowfading put fundamental limits to the sensing performance and practical entailments in designing of cognitive vehicular networks. Extensive modeling efforts are then being carried out to cope with varying channel characteristics, particularly multipath fading and shadowing. In this paper, the authors examine the performance of spectrum sensing using ED over ...