Many proposals have studied the optimization of the EDCA mechanism used by the IEEE 802.11p MAC layer to provide QoS. In this work, we focus on the queuing process done by the different Access Categories (ACs). We propose the use of a single common buffer with a prioritized buffer allocation algorithm inspired on the MAX-MIN principle for a fair sharing of a common resource. We test the proposed algorithm with a fixed and a dynamic guaranteed queue size for each AC. Results obtained from simulations in a multihop VANET scenario show that our approach outperforms traditional queuing used in MAC 802.11p.