The report summarizes the findings from comparative studies of safety performance between two different types of High Occupancy Vehicle (HOV) facilities in California - continuous access versus limited access. The findings show that HOV facilities with limited access offer 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 present research, the authors investigated the relationship between HOV design features and safety performance of HOV facilities. One key design feature is shoulder/total width. The findings 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 is provided. Additionally, findings from investigating other influential factors on safety performance of HOV facilities, including design features of ingress/egress section in limited access HOV facilities, congestion, High Collision Concentration Locations and etc., were also documented. While further research is needed, results to date suggest that improvements in HOV facility performance can be achieved by improved HOV facility design.
March 10, 2009