Providing quality travel conditions to High Occupancy Vehicles (HOVs) is essential for travel demand control and High Occupancy Toll (HOT) lane system operations. In most HOT lane systems converted from previous HOV lane facilities, physical barriers or double white lines are utilized to separate HOT lane from General Purpose (GP) lanes. Only specified merging areas are available for both HOVs and Single Occupancy Vehicles (SOVs) to access or exit HOT lane. These spatial restrictions as well as the interruption of flow progression caused by the increased weaving movements may deteriorate HOV travel conditions. Quantitative analysis on HOVs travel condition under different traffic conditions is very important for understanding the HOT lane impact on HOV travel and for optimizing overall HOT lane system operations. This study concentrates on investigating HOV travel conditions in the HOT lane system with various HOV proportions under different traffic conditions. A simulation-based HOT lane operation analysis is conducted. A microscopic traffic simulation software tool, VISSIM, is utilized and an external module to enable dynamic HOT lane operations is developed. The Washington State Route (SR) 167 HOT lane system is simulated. The research findings indicate that under current traffic demands HOT lane system can improve overall HOV travel conditions due to the overall system performance enhancement. However, negative impacts of HOT lane systems on HOV travelers become significant with increased traffic demands. This study demonstrates quantitative impacts of HOT lane systems on HOV travelers and provides in-depth analysis for HOT lane performance evaluations.