EVALUATION OF THE SEATTLE I-5 NORTH HIGH-OCCUPANCY VEHICLE LANE 2+ OCCUPANCY REQUIREMENT DEMONSTRATION

High-occupancy vehicle (HOV) facilities allow for a great deal of operational flexibility. This flexibility has often been noted as one of the advantages of HOV lanes. The ability to change the vehicle occupancy level required for use of the HOV facility reflects this flexibility. Increasing or decreasing the occupancy requirement provides one approach to managing the demand on the facility and thus the number of vehicles and people using the facility. The impact of increasing and decreasing vehicle occupancy requirements has been a topic of discussion at recent national HOV conferences and other meetings. Although a few areas, most noticeably Houston, have documented the impact of changes in HOV lane vehicle occupancy levels, more information is needed to fully understand the consequences of these changes. This paper summarizes the impact of one such change: the domonstration project in which the minimum vehicle occupancy requirement on the I-5 North HOV lanes in Seattle was lowered from three or more persons per vehicle to two or more persons per vehicle. The impact of this change on the I-5 North HOV lanes and the general-purpose lanes is documented in this paper. The information presented assists in enriching the understanding of the consequences of changing HOV lane vehicle occupancy requirements.