Vehicular Ad-hoc Networks (VANETs) have attracted a lot of attention in the research community in recent years due to their promising applications. VANETs help improve traffic safety and efficiency. Each vehicle can exchange information to inform other vehicles about the current status of the traffic flow or a dangerous situation such as an accident. The Application for V2V and V2I can be divided into the following three services: safety services, traffic management and user-oriented services. Safety services have special requirements in terms of quality of service. In fact, bounded transmission delays as well as low access delays are mandatory in order to offer the highest possible level of safety. At the same time, user-oriented services need a broad bandwidth. Medium Access Control will play an important role in satisfying these requirements. In VANETs, the nodes share a common wireless channel by using the same radio frequencies and therefore an inappropriate use of the channel may lead to collisions and a waste of bandwidth. Hence, channel sharing is the key issue when seeking to provide a high quality of service. Road safety and traffic management applications require a reliable communication scheme with minimal transmission collisions, which thus increase the need for an efficient Medium Access Control (MAC) protocol. This protocol must be designed to share the medium between the different nodes both efficiently and fairly. However, the design of the MAC in a vehicular network is a challenging task due to the high speed of the nodes, the frequent changes in topology, the lack of an infrastructure, and various QoS requirements. In this thesis we introduced a new hybrid MAC protocol with TDMA-CSMA/CA multiple access in a cluster-based topology. In TDMA period we have to select a cluster head as a central coordinator. In this protocol, we use TDMA to guarantee the channel access for all nodes to send/receive their safety message and CSMA/CA method to service channel reservation for nodes who have non-safety message for transmission. Simulation result show that our proposed scheme has improved throughput and channel utilization in CSMA/CA period and control channel access delay in TDMA period in compare of present standard. Keywords: Vehicular Ad-hoc Networks, MAC Protocols, Collision, Hybrid Multiple Access based on TDMA-CSMA/CA