The current medium access control (MAC) protocol of the wireless access in vehicular environments (WAVE) system is based on IEEE 802.11 distributed coordination function (DCF) and enhanced distributed channel access (EDCA), which have drawbacks in supporting throughput-sensitive applications in high density networks, e.g. future vehicular ad-hoc networks (VANET). In order to address the problem, we propose a novel MAC protocol, namely vehicular MESH network (VMESH), which is specifically designed for the control channel (CCH) and multiple service channels (SCHs) architecture of WAVE system. A synchronized and distributed beaconing scheme is employed by the VMESH protocol for the purposes of neighborhood awareness and dynamic channel resource reservation. In this paper, we present the advantage of VMESH protocol under saturated traffic load condition through theoretical analysis. For more realistic scenarios with mobility and unsaturated traffic loads, through the simulative study, we can also show that the VMESH protocol outperforms the WAVE protocol when the traffic load is heavy.