Connected vehicles will be a prominent feature of future Intelligent Transport Systems. Which means that there will be a very high volume of wireless traffic that vehicles will receive and process. Due to this large quantity of traffic, there will be Quality of Service (QoS) constraints on the system that means messages will need to be prioritised. As vehicles will have a finite buffer to hold messages, the prioritisation scheme must consider network throughput to ensure QoS requirements are met. In our throughput authentication prioritisation technique, a Markov model is used to detect abnormally large data traffic users who are potential attackers performing a Denial of Service (DoS). Our results show that the algorithm can efficiently enhance network throughput.