Road safety prevents road users from road accidents like pollution and traffic congestion. In Vehicular Ad-hoc networks (VANET), the reliability of communication-related to road safety is very important for vehicular nodes. However, some researches show that the safety-message transmission in VANET could also be congested under road safety application because of channel interference. Therefore, the increasing of spectrum resources is a good way to solve transmission congestion. Hence, we use cognitive radio enabled VANET(CR-VANET), where CR device can detect possible idle spectrum for VANET communication system and assist on time broadcast safety-message. With high-speed mobility of vehicular nodes and highest channel availability of prediction method to avoid mutual channel interference and to reinforce road safety applications to make sure that support top quality of service requirements with fair channel allocation model in CR-VANET. Depending on this highest probability of channel availability prediction method, we will avoid channel mutual interference and enhance road safety applications employing a fair channel allocation model or fairness (Jain index) with PUs of vehicular nodes in CR-VANET. Specifically, the proposed fair channel allocation model has 5 percent detection performance improvement at false alarm probability of 0.2, decreased the probability of access conflict by 7 percent at 14 MHz CR, improved probability of application-level packet reception(PRP) by 1.1 percent at vehicular node density of 0.45 veh/m2 and decreased Probability of Application-level delay by 1.8 percent at vehicular node density of 0.45 veh/m2 as compared with channel availability prediction method. By using the main evaluation parameters that highly affect the fairness probability of fair channel allocation model in CR-VANET that are the number of vehicular nodes and number of channel availability with( Matlab, Simulink, and vanet toolbox) used as the tools in CR-VANET. Keywords: Road safety, Vehicular Ad-hoc Network(VANET), Cognitive Radio(CR), and Fair Channel allocation model.