GOLDEN GATE BRIDGE MOVEABLE MEDIAN BARRIER
UPDATED JANUARY 2007
The Golden Gate Bridge, San Francisco, CA, is recognized as an icon of striking grace and beauty, as well as a vital transportation link in California’s highway system and as an engine of economic vitality supporting the San Francisco Bay Area’s commerce and tourism. With more than 10 million tourists visiting each year and 40 million vehicles crossing the span annually, the agency that maintains and operates the span, the Golden Gate Bridge, Highway and Transportation District (District), is continually focused on advancing and enhancing its safety measures to best protect the traveling public.
The Golden Gate Bridge roadway is 1.7 miles long. The span’s six-lane roadway includes curb lanes that are 11-foot-wide and the remaining four lanes are just 10-feet wide. Traffic travels across the span in opposing directions separated by 19 inch-tall, 4 inch diameter plastic tubes, spaced at 25 foot intervals. The tubes are manually placed in sockets in the Bridge roadway to identify the San Francisco outbound lanes and San Francisco inbound lanes and are reconfigured several times per day to match the direction of peak traffic flow.
With its narrow roadway lanes and tight curves at either end, coupled with its high traffic volumes, and frequently foggy and windy conditions, the installation of a one-foot-wide moveable median barrier (MMB) is a proposed safety enhancement intended to eliminate crossover collisions. The MMB system includes the barrier—12-inch wide and 32-inch high steel clad units filled with high density concrete tightly pinned together to form a semi-rigid median barrier—and the barrier transfer machines.
The District conducted an extensive study of a wider (two-foot-wide) MMB technology in the 1980s and found it to be infeasible. With the emergence of a narrower one-foot wide barrier in 1996, the District immediately launched a comprehensive analysis that lead to the conclusion that, with some operational trade-offs, a barrier will virtually eliminate crossover accidents. The next step towards installation is to perform the detailed engineering and environmental analysis leading to final design.
The District operates both the Bridge and its public transit system, Golden Gate Bus and Ferry Transit, with no taxing authority, receives very limited state and regional funds, and relies heavily on its local toll revenues to support on-going Bridge operations, maintenance and its post 9-11-01 expanded security program. To advance the next phase of engineering and environmental analysis, $5 million is required. The District is seeking $5 million in outside funding so that this safety enhancement project is able to move forward. It is estimated that final design and construction will cost another $20 million.
The smooth and safe flow of traffic across the span has been continually enhanced through a number of operational and safety features including the utilization of one-way toll collection and reversible lanes since the 1960s, reduction of the speed limit to 45 MPH, increased law enforcement patrols, and widening of the roadway from 60 to 62 feet-wide in the 1980s, establishing the span as a special driving zone and increasing the use of the most modern radar enforcement equipment in the 1990s, implemented electronic toll collection and installed a safety railing to better separate traffic lanes from pedestrian sidewalks in 2000s.
Simulated image of the “zipper” truck moving a Moveable Median Barrier on the Golden Gate Bridge:
