In this study, PATH investigated safety performance between two different types of High Occupancy Vehicle (HOV) facilities in California – continuous vehicle access versus limited vehicle access. Collision data from 1999 and 2003 along 824 miles of freeways with HOV facilities was examined, including 279 miles of HOV lanes with continuous access and 545 miles with limited access. The HOV facilities analyzed make up about 60% of all HOV lanes in California. The findings from this study showed that HOV facilities with limited access offered no safety advantages over those with continuous access, whether measured by percentage of collisions, collisions per mile, collisions per VMT, or collision severity. As part of the research, the relationship between HOV design features and safety performance of HOV facilities was explored. One key design feature was shoulder/total width. The results indicate that maintaining adequate shoulder and total width is essential, and a quantitative estimate for the relationship between shoulder and total width versus safety performance of HOV lanes was developed. As a result of this study, Caltrans made a policy shift to implement continuous access for a new facility and covert the access type on selective corridors already in existence in Southern California.