Additional Information - Moveable Median Barrier Project

BackgroundAccident RateMMB Studies Since 1996


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.

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 launched a comprehensive analysis that lead to the conclusion in May 1998 that, with some operational trade-offs, a barrier will virtually eliminate crossover accidents.

Accident Rate is 3 times Lower Now than in the 1980s

The accident rate on the Golden Gate Bridge is lower today than it was in the 1980s largely due to the reduction in the speed limit to 45 MPH in the 1980s, widening the roadway from 60 to 62 feet-wide in the 1980s, increased law enforcement patrols, establishing the span as a special driving zone and increasing the use of the most modern radar enforcement equipment in the 1990s. Further, the Bridge was designated a Safety Awareness Zone in January 2007.

From calendar year 1971 through September 27, 2007, during which there were more than 1.4 billion crossings, there were 36 fatalities, of which 16 were from head-on collisions. The last fatality was on July 3, 2001. By 1998, the accident rate was 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.

Summary of Moveable Median Barrier Actions Taken - 1996 to 2012

In 1996, with the emergence of a new and narrower one-foot wide barrier, the District launched a comprehensive analysis that lead to the conclusion that, with some operational trade-offs, a barrier will virtually eliminate crossover accidents. On July 12, 1996, the Board by Resolution 96-163, authorized the District’s financial participation, in the amount of $42,500, in the crash test of the new BSI one foot wide MMB. The Board also authorized engaging services of Northwestern to evaluate various traffic and safety ramifications of the installation of the new one foot wide MMB on the Bridge.

Following crash testing in March 1997, Northwestern completed its report titled Traffic Safety Study dated October 29, 1997. Professor Robert K. Seyfried, Northwestern, presented the findings of the report to the Building and Operating Committee of the Board in December 1997. Professor Seyfried explained that the report concluded that the decision is a virtual toss-up, and the Board could reasonably make a decision either way—install a MMB or forgo installation of a MMB. The Board’s final decision must result from a balancing of factors and considerations, which in turn would require the Board to determine which considerations and factors are most important.

On May 22, 1998, the Board, by Resolution 98-116, authorized a conceptual approval for the installation of the BSI one foot wide MMB on the Bridge and authorized staff to investigate acceptable solutions to the many remaining technical and operational items (approximately 28 different items) that must be resolved prior to installation. Additionally, the Board directed staff to develop a cost estimate for the MMB installation, identify necessary permits, and to begin to identify possible funding sources.

A phased approach would be implemented to resolve the many remaining technical and operational issues identified as part of the May 1998 conceptual approval process.

In August 1999, the Board authorized the first of several studies of some of these unresolved technical and operational issues as part of a preliminary engineering evaluation and, by Resolution 99-175, authorized Parsons Brinckerhoff (PB), San Francisco, CA, to perform the following services, as Phase I, relative to the possible installation of a MMB:

  1. Evaluate MMB end treatment and anchorage schemes at the toll plaza.
  2. Evaluate storage requirements for the Barrier Transfer Machine (BTM) at the north end.
  3. Evaluate strategies for delineation of traffic lanes on the Bridge with a MMB installed.
  4. Develop emergency response procedures for accidents or incidents that require emergency response across or through a MMB.

PB’s findings were presented in two reports: 1) Conceptual Engineering Design Studies and, 2) Emergency Operations Report. PB concluded that possible engineering solutions may exist for those aspects of a MMB installation that were studied, subject to further design and development during a future detailed engineering design phase, provided that the Board accept the various trade-offs involved in those proposed solutions. PB also concluded that existing emergency response procedures would have to be modified and/or supplemented to provide satisfactory emergency response with a MMB present, again with the recognition that such procedures may have certain drawbacks and involve certain trade-offs.

On March 9, 2001, by Resolution 2001-044, the Board accepted PB’s findings and authorized PB to conduct Phase II studies:

  1. Evaluate the traffic congestion impact of decreasing lane widths on the Bridge with the MMB installed.
  2. Evaluate the impact of the MMB on traffic congestion associated with traffic accidents and stalls on the Bridge.

In January 2002, PB reported their findings in Movable Median Barrier Feasibility Studies—Phase II and provided the following conclusions:

  1. Placing a MMB on the Bridge 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, however, has certain drawbacks.
  2. Installation of a MMB on the Bridge could theoretically result in a reduction in capacity in the two- and three-lane configurations, but it is also possible that this capacity reduction may not occur. The ultimate result is not certain.
  3. 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; but this type of accident causes significantly greater delays per accident.
  4. 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.
  5. 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 Phase I and Phase II studies performed by PB did not address all of the technical and operational issues identified previously in Resolution 98-116 authorized by the Board on May 22, 1998. However, of the issues that were studied, none categorically ruled out installation of a MMB on the Bridge, but as reported in the findings, the possible resolution of those issues involved balancing of pros and cons and acceptance of trade-offs.

To address the remaining technical and operational issues outlined in the May 22, 1998 Resolution 98-116, and to answer many of the final operational, engineering and cost details, it is necessary to proceed with detailed design and environmental studies.

On April 12, 2002, the Board, by Resolution 2002-045, approved the following actions:

  1. Accept PB’s January 2002 Movable Median Barrier Feasibility Studies–Phase II Report.
  2. Direct staff to develop a funding plan for detailed design and environmental studies.

On March 11, 2005, as part of Resolution 2005-015, the Board authorized the Board President to form an Advisory Committee of the Board for Bridge Barrier Projects to work with staff to identify and pursue funding for implementation of the studies associated with both the Physical Suicide Deterrent System and the MMB system projects.

In late 2007 and early 2007, required Wind Tunnel Testing was conducted on the MMB. When any modification is contemplated for the Golden Gate Bridge, it is essential that they are tested for wind stability to ensure that there is no negative impact to the wind dynamics of the span. Wind tunnel testing was done on the MMB in conjunction with three generic design concepts for a suicide barrier on the span. It has been determined that a MMB can be added safely to the Bridge without negatively impacting the wind stability of the Bridge.

In June 2008, a Request for Proposal was issued to solicit consultants to work with the District to complete the legally required detailed design and environmental studies - Environmental Studies and Preliminary Design for a MMB on the Golden Gate Bridge. The scope of the services generally consisted of: Preparing environmental studies pursuant to state and federal requirements; Developing preliminary design and cost estimates for the MMB system, including facilities to store and maintain the barrier transfer machines; Exploring, developing, evaluating and reviewing, from a traffic operations and environmental perspective, potential design variations for a MMB on the Bridge.

On September 12, 2008, the District’s Board of Directors approved a Professional Services Agreement (PSA) for Environmental Studies and Preliminary Design for a MMB on the Golden Gate Bridge to AECOM, USA, Inc. (formerly DMJM Harris), to perform preliminary engineering and environmental studies.

In 2009, the Environmental and Preliminary Design work began. The consultant developed conceptual designs regarding how the moveable median barrier will safely transition and terminate (from a traffic operations perspective) on the Waldo Grade and at the south end of the bridge. The consultant prepared and submitted the Preliminary Environmental Studies (PES) form to Caltrans.

The MMB will include two transfer machines (aka “zipper” trucks) and 13,340 feet of barrier. This system will replace the current lane diversion system that involves the manual movement of yellow pylons that delineate the direction of traffic lanes. The project budget is $26.5 million with funding coming from three sources: $20 million from the Metropolitan Transportation Commission; $1,379,200 in federal funds, and the remainder coming from Gate Golden Bridge toll revenues.

February 1, 2010: A meeting was held with Caltrans to review the appropriate type of environmental document needed for the project and to perform a site review.

March 15, 2011: Staff met with the consultants to discuss issues regarding the draft environmental and technical studies required for the project. The consultant has submitted to Caltrans for review and approval the preliminary cost estimate, the proposed geometric alignment modifications, the Natural Environment Study [Minimal Impacts] (NESMI) Report, the Visual Impact Assessment Report (VIAR), the Traffic Engineering and Analysis Report (Traffic Study), the Cultural Resources (Section 106 Finding of Effect [FOE]) Report and the Section 4(f) Report. Section 4(f) of the Department of Transportation Act of 1966 requires that an evaluation must be made to determine if a proposed project will cause any impacts to any significant publicly owned public park, recreation area, or wildlife and waterfowl refuge, and any land from an historic site of national, state, or local significance.

October 26, 2011, November 3, 2011, and December 1, 2011: District staff met with Caltrans to discuss the reports. Caltrans has approved all of the reports except for the Traffic Study.

January 17, 2012: Revised Traffic Study and Design Exceptions fact sheets were resubmitted to Caltrans incorporating previous comments from Caltrans.

February 14, 2012: The District met with Caltrans on to review the changes submitted in January.

April 6, 2012: The District received Caltrans’ written comments on the revised Traffic Study and Design Exceptions fact sheet noted above (January 17, 2012) and has responded to the comments. District is waiting for Caltrans’ comments. Staff has reviewed the 35% completion design plans and proposed changes to the lane striping. The consultant evaluated the impact of the proposed change on traffic operations and determined that traffic operations will be improved.

May 24, 2012: The Board authorized the General Manager to execute a Cooperative Agreement with Caltrans that outlines the coordination of responsibilities for environmental evaluation, design and construction of the portion of the Golden Gate Bridge moveable median barrier to be installed within the State Highway 101 right-of-way north and south of the Golden Gate Bridge. The Cooperative Agreement was executed on June 14, 2012. The District met with Caltrans on July 16 and July 31, 2012, and reviewed the outstanding comments on the Traffic Study, Geometric Design and Design Exceptions. Caltrans requested additional information regarding the traffic operations within Caltrans’ right-of-way north of the bridge north abutment. The District has submitted the requested information to Caltrans for review. The District met with Caltrans on August 16, 22, and 28, 2012, to review Caltrans’ comments and modifications to the Traffic Report in response to Caltrans’ comments. Caltrans provided additional comments on September 10, 2012.