Cognitive Radio (CR) is extending the applications of wireless communications worldwide. Cognitive radio verifies the electromagnetic spectrum availability and permits the modification of the transmission parameters using the interaction with the environment. The goal is to opportunistically occupy spectral bands with minimum interference to other users or applications. Cognitive radio for Vehicular Ad hoc Networks (CRVs or CR-VANETs) is a new trend in the automotive market. Recent and future vehicles will offer functionalities for the transmission of intra-vehicular commands and dynamic access to wireless services, while the car is in transit. This paper describes the cognitive radio technology and its signal processing perspectives for the automotive market.