Real-time dependable communication requires deterministic transmission instants and bounded latency for inter-vehicular communication. Carrier Sense Multiple Access (CSMA) has serious drawbacks in what concerns to the timeliness of the communications, since it allows collisions to happen in the channel and it may cause unbounded delays before channel access. This paper proposes an enhanced version of the Vehicular Flexible Time-Triggered (V-FTT) protocol, a deterministic MAC protocol for vehicular communications. Proposed enhancements include novel schemes to protect V-FTT compliant nodes from the interference of non-compliant nodes, which can only transmit during specific slots, the Free Period. These mechanisms were implemented and validated in an ITS G5 station, the IT2S platform.