VANET is used to create a mobile network that is based on mobile vehicles such as cars. It is a sub category of MANET. It allows every participating vehicle into a wireless node, allowing it approximately 100 to 300 meters of each other to connect and in turn, create a wide range network. In this network vehicles can join into one another so that a mobile internet is created. It is used for ITS (Intelligence Traffic System). Very well-known automotive companies like BMW and Ford promotes this term. In VANET the mobile nodes are well equipped with ORT (On board Radio Transponder) that is useful in communication with other nodes in a network. In order to establish communication among the vehicles VANET comes with communication points by road infrastructure. There are several security attacks possible in VANET such as Sybil attack, selfish driver attack. In this paper we proposed a Request Response Detection Algorithm (RRDA) which is used to detect DOS after APDA. This increases the response time and maximizes the security in VANET. © 2014 IEEE.