Current link layer protocols for safety-related inter-vehicle communication networks suffer from significant scalability and security challenges. Carrier Sense Multiple Access (CSMA) approaches produce excessive transmission collisions at high vehicle densities and are vulnerable to a variety of Denial of Service (DoS) attacks. Explicit time slot allocation approaches tend to be limited by the need for a fixed infrastructure, a high number of control messages, or poor bandwidth utilization, particularly in low-density traffic. This paper presents a novel adaptation of the explicit timeslot allocation protocols for IVC networks. The protocol requires no control messages, provides protection against a range of DoS attacks, significantly improves bandwidth utilization, and automatically adjusts the timeslot allocation in response to changes in vehicle densities.