In this paper, the effective channel usage is investigated in IEEE 802.11p WAVE (Wireless Access in Vehicular Environments) communication protocol. IEEE P1609 family is the standard for wireless access in vehicular environments based on IEEE 802.11p, and the WAVE architecture with multi-channel operation over CCH (Control Channel) and SCH (Service Channel) are defined in the MAC layer. However, there is only one channel (CCH or SCH) that is used to transmit data and the other one will be wasted during service access. Thus, an Exploitable Node-Assisted WBSS (WAVE Basic Service Set) Broadcasting Mechanism is proposed to utilize empty channels and idle nodes for transmitting WBSS to newly coming nodes. The proposed mechanism can reduce the delay time for getting service information from RSU when vehicles are traveling into the broadcasting coverage of RSU. The Sync interval is fixed in the original scheme for guarantee OBU getting WBSS in a specific period. But, this feature may cause bandwidth wastage during service access. Therefore, a Dynamic Sync Interval Scheme is proposed to improve the channel usage. In this paper, we exhibit merits and performance results of our proposed schemes.