Vehicular Ad hoc network is considered as an important component of the next generation automotive systems. The various safety applications supported by the vehicular communication depend on the reliable delivery of the periodic safety messages. Due to variable vehicle density on the road, the fixed transmission parameters such as transmission range and packet generation rate of the safety messages result in a large number of collisions and an inefficient use of the control channel. The safety applications demand the adaptation of the above transmission parameters without compromising the safety of the vehicles. In this paper, we present a combined transmission range and packet generation rate control algorithm which takes into account the safety of the vehicles and maximizes the control channel utilization. At first, every vehicle calculates its packet generation rate using the measured time headway metric which provides a measure of the vehicle safety. In the second step, the transmission range is adapted based on the vehicle density estimation, the target network load and the packet generation rate of each vehicle. The performance analysis shows that the proposed algorithm improves the safety message performance in terms of packet reception rate and control channel utilization for a range of vehicle densities and vehicle speeds.