The Golden Gate Bridge (Bridge) is 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 Golden Gate Bridge, Highway and Transportation District (District) is continually focused on advancing its safety measures to best protect the traveling public.

The Bridge roadway is 1.7 miles long with a six-lane roadway that includes 11-foot-wide curb lanes 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 roadway to identify the San Francisco outbound lanes and San Francisco inbound lanes and are reconfigured several times per day the to match the direction of peak traffic flow.

With its narrow roadway lanes and tight curves at either end of the span, coupled with its high traffic volumes, and frequently foggy and windy conditions, the installation of a one-foot-wide moveable median barrier (MMB) would virtually 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. It also includes a barrier transfer machine. This technology is now proven to provide low deflection or movement and high stability when hit by vehicles at varying speeds.

Estimated Project Cost
The $25 million project is not yet funded. However, the Metropolitan Transportation Commission (MTC) has recently indicated to the District that they will fund $20 million (80%) of this project, with the District funding remaining $5 million (20%) from toll dollars. Discussions are still underway to finalize this funding, and there has been no action taken by MTC at this time. This funding must be approved by the MTC full commission, and it is currently anticipated that it will come forward in November 2007.

The next phase of work for the MMB is the necessary Engineering and Environmental Analysis, which will require $3 million and take less than two years to complete. Once funding is approved, this work could begin by early 2008.

It is estimated that final design and construction will cost $22 million. It is estimated that the MMB installation could occur by 2010.

MMB Studies Undertaken in the 1990
In September 1996, the District hired Northwestern Traffic Institute to conduct a detailed traffic engineering and safety analysis of the one-foot wide MMB to determine the impacts of installation of a MMB system on safety and traffic operation characteristics of the Bridge.

In May 1998, the Board approved, by Resolution No. 98-116, the conceptual installation of a one-foot wide MMB developed by Barrier Systems Inc. (BSI) on the Bridge. The Northwestern Traffic Institute concluded that, given the various trade-offs, a reasonable Board could decide to either install or not install the barrier. However, notwithstanding the risks and uncertainties, staff based its recommendation to move forward with installation on the fact that the proposed MMB would virtually eliminate crossover accidents.

In May 1998, it was also noted a series of operational and planning issues yet to be resolved including identifying funding sources; obtaining required planning review permits and approvals from Golden Gate National Recreation Area and review and concurrence from Caltrans; developing an emergency vehicle response plan; developing an acceptable lane marking and configuration plan; developing an anchorage and buffering system at the barrier ends; designing the transfer vehicle storage and maintenance facility; engaging consultants and conducting environmental analyses including cultural and historical evaluation; developing and installing the guidance system; constructing, fabricating, and installing the barrier system and the associated transfer vehicle and storage facilities; testing the entire system once developed; negotiating a contract with BSI.

In 1999 (Resolution No. 99-175), the Board authorized studies of several of these outstanding issues: Evaluate MMB end treatment and anchorage schemes; Evaluate storage requirements for the Barrier Transfer Machine at the north end of the Bridge; Evaluate strategies for delineation of traffic lanes on the Bridge; and Develop emergency response procedures for accidents or incidents that require emergency response across or through a barrier. The results were presented in two reports: Conceptual Engineering Design Studies and Emergency Operations Report. These reports indicated that possible engineering solutions may exist for those aspects of a MMB installation that were studied, subject to further design and development during the Engineering and Environmental phase of the project, and provided that the Board determines to accept the various trade-offs involved in those proposed solutions. It was also concluded that existing emergency response procedures might be modified and/or supplemented to provide satisfactory emergency response with a MMB present, with the recognition that such procedures may have certain drawbacks and involve certain trade-offs.

In March 2002, the Board accepted the result of additional analysis in the report Movable Median Barrier Feasibility Studies – Phase II which made the following conclusions:

Placing a MMB will result in decreased lane widths in at least two lanes at any one time. While there is no “perfect” lane configuration, there are several potentially viable lane configurations, each of which has certain drawbacks.
Installation of a MMB could theoretically result in a reduction in traffic capacity in the two- and three-lane configurations (not a reduction in roadway lanes—just in the amount of traffic that can flow across the Bridge at a given time). It is also possible that this capacity reduction may not occur. The ultimate result is not certain.
Installation of a MMB on the Bridge would result in a virtual elimination of crossover head-on accidents. Head-on fatal accidents occur less frequently than other types of accidents; however, this type of accident causes significantly greater delays per accident. Installation of a MMB would result in certain other types of accidents (e.g. rear enders in the two lane direction) being more difficult to clear due to the presence of the barrier, resulting in longer delays than the current condition for these accident types. It is assumed that the introduction of a MMB on the Bridge will not result in a change in the overall accident rate, but this is not certain. The elimination of delays associated with crossover accidents might be offset by the increase in delays caused by non-crossover accidents. Over the course of a year, as opposed to a per incident basis, overall delays associated with accidents may not significantly change, but again this cannot be predicted with certainty.

The three reports submitted to date since May 1998 have not studied all of the operational and planning issues identified in Resolution No. 98-116 (May 1998).

The next step is the Engineering and Environmental Analysis which will consist of the following:

  • Evaluate the proposed project pursuant to the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA);
  • Evaluate the proposed project pursuant to state/federal historic preservation laws;
  • Coordinate planning efforts with the National Park Service and the State of California, Department of Transportation;
  • Evaluate right-of-way issues with the National Park Service and the State of California, Department of Transportation;
  • Design and evaluate environmental impacts associated with the storage facility for the barrier transfer machines;
  • Prepare plans and a detailed estimate.

MMB Studies in the 1980s
In the 1980s, the District conducted an extensive study of a wider (two-foot wide) MMB technology and found it to be infeasible. With the emergence of a narrower one-foot wide barrier in 1996, the District launched a comprehensive analysis that lead to the conclusion that, with some operational trade-offs, a barrier will eliminate crossover accidents. Now, the District must advance this critical project through detailed engineering and environmental design leading to final design and installation of a MMB.

Accident Rate at GGB
From calendar 1971 through September 27, 2007, there have been 36 fatalities on the span with more than 1.4 billion crossings. The last one was on July 3, 2001.

In 1998, the accident rate on the Bridge had been reduced by nearly one-half since the period of 1981 through 1983 when the rate was 1.25 accidents per million vehicle miles. In the years 1991 through 1995, the accident rate was 0.64 accidents per million vehicle miles. The accident rate has been further reduced since the implementation of a double-fine-zone in 1996 to a rate of 0.61 accidents per million vehicle miles for the period of 1991 through 1997.

Past Safety Improvements Undertaken
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, widening of the roadway from 60 to 62 feet-wide in the 1980s, establishing the span as a double fine zone and increasing the use of the most modern radar enforcement equipment in the 1990s, implementation of an electronic toll collection and installation of a safety railing to better separate traffic lanes from pedestrian sidewalks in 2000s. Further, the Bridge was designated a Safety Awareness Zone in January 2007.