In this paper we propose the Slot Reservation Announcement (SRA) access scheme to minimize the occurrence of channel-access collisions in infrastructure IEEE 802.11 networks under emergency and crowded scenarios. SRA is based on slot reservation in lieu of a randomized backoff approach to increase the channel-access success ratio. The proposed scheme rids IEEE 802.11-like access networks of throughput and utilization collapse under crowded scenarios. In turn, it increases channel utilization. This enabled access is critical for crowded networks under emergency scenarios where many stations suddenly contend for the channel. This scheme may be used as fallback mechanism to avoid throughput collapse in such scenarios and to enable critical communications. Our simulation results show maximum bandwidth utilization and increased throughput as compared to an IEEE 802.11 network and a recent reservation-based access scheme under crowded conditions.