The Golden Gate Bridge, known as one of the most beautiful bridges in the world, serves 110,000 vehicles per day, connecting San Francisco to inland as a segment of Highway 101 in California. The average peak hour volume over 6,500 vehicles per hour exceeds the traffic capacity of three lanes on each direction. Due to unique function of the bridge as a gateway of San Francisco, the peak directions in the morning and afternoon were explicitly distinguished. Recurrent traffic delay on the peak direction deteriorated level of service during the commute periods and caused user’s inconvenience and traffic accidents. The workers previously used to move plastic delineators to change lane configuration (4-2, 3-3, and 2-4) in several times a day. Neither did it provide prevention nor physical protection from the head-on collision on the bridge section. In January 2015, the Golden Gate Bridge was completely closed for two days to install the moveable median barrier (MMB) system, Road Zipper®, for more effective and safer variable lane management than the previous operation. One-meter section with 30.48 cm wide of highly reinforced concrete barriers are linked to form a continuous barrier wall and the machine lifts and passes the barriers through a conveyor system at a seeds up to 16 km/h. The MMB enables to quickly reverse lane configuration without traffic closure, providing more lanes to the peak direction as well as eliminating head-on collision on the bridge deck by presence of a physical structure. The traffic monitoring study result shows the significant improvement of average speed during peak hours and the regional traffic accident records shows improvement of safety after implementing the MMB on the Golden Gate Bridge. According to the traffic accident records, 13 injuries occurred in five accidents of vehicle collision in two-directions from 2007 to 2014 but no two-way accident has been reported since the operation of the Road Zipper® began. Furthermore, the MMB would be effectively implemented on construction work zones, managed lanes, variable lane management and other traffic operation to improve traffic safety and maximize utilization of roadway facilities.

• Changmo Kim(Department of Civil and Environmental Engineering, University of California)