While many existing rate adaptation schemes in IEEE 802.11 Wireless LANs result in severe throughput degradation since they do not consider the collision effect when selecting the transmission rate, CARA (Collision-Aware Rate Adaptation) [1] shows improved system performance thanks to its collision-awareness capability. In this paper, we propose two enhancements to the original CARA scheme to further improve the system performance. The first one is called CARARI, which extends CARA’s collision-awareness capability in making rate increase decisions, while the second one, called CARA-HD, incorporates a hidden station detection mechanism. Simulation results show that the proposed schemes outperform the original CARA significantly under various randomly-generated network topologies.