A dual step energy detection based spectrum sensing algorithm for cognitive vehicular ad hoc networks Intelligent Transportation Systems (ITS) are fundamental in order to improve safety and road efficiency. In this framework inter-vehicle communications play a primary role. To this aim several vehicle-to-vehicle (V2V) communication standards have been developed. The most important is IEEE 802.11p that operates in ISM band (5.85-5.92) GHz. Unfortunately at these frequencies communication ranges are limited and Doppler effect could not be neglected, especially when the carrier spacing of the adopted modulation techniques is close to 1 kHz, as it happens in modern standard for digital mobile communications. In order to overcome these issues, a possible solution could be the adoption of a dynamic spectrum access model able to identify frequency holes in UHF band. In this framework, this paper presents a novel approach to spectrum sensing based on the application of a dual step energy detection algorithm. It has been designed and tailored to be effective in identifying DVB-T signals. A test campaign carried out in simulation environment has confirmed the goodness of the proposal.