Bay Crossings Study

San Francisco Bay Crossings Study History

Background
Several times over the past 30 years, Bay Area transportation planners, officials and voters have considered proposals for a toll bridge crossing the San Francisco Bay south of the existing San Francisco- Oakland Bay Bridge. These earlier proposals and studies revolved around the concept of a new auto bridge located approximately 4 miles south of the San Francisco-Oakland Bay Bridge. The now-defunct California Toll Bridge Authority authorized a new bridge in April 1966 extending from India Basin in San Francisco to Alameda, Oakland and San Leandro, and appropriated funding for study and preliminary design. This alignment was studied in 1971. Shortly afterward, voters were given a chance to vote on this new bridge through a 1972 proposition. Voters in Alameda, Marin, Contra Costa, San Francisco, Santa Clara and San Mateo subsequently rejected the proposition. It is generally assumed that the voters and local officials opposed the bridge due to environmental concerns and concerns on the impact to the nascent BART transbay service.

1991 Bay Crossing Study
The most recent study of transbay travel and new transbay transportation facilities was done in 1991 by MTC in response to a State Senate resolution (Senate Concurrent Resolution 20 - Kopp). SCR 20 specifically cited current and growing congestion on the San Francisco- Oakland Bay Bridge and BART as a reason for considering improvements to transbay travel. However, rather than focusing solely on a new auto bridge, the 1991 Bay Crossing Study took a broader approach. In addition to studying what would happen if no new facility were built (called the Baseline), it examined eleven different "build" alternatives for improving transbay travel. These were:

High-Speed Ferry and Operational Upgrade
Southern Crossing Bridge
Southern Crossing tunnel
Interstate 380 to I-238 bridge (with BART)
Interstate 380 to I-238 tunnel (with BART)
BART SFO/OAK airport connection
BART Alameda to Candlestick connection
New BART Transbay Tube
Airport peoplemover connection
Railroad Airport connection
Intercity rail connection

The policy committee established by SCR 20 ultimately reduced the number of alternatives carried forward into detailed study to five. These were alternatives 1, 4, 6, 8 and 11. The 1991 San Francisco Bay Crossing Study (also known as the SCR 20 Study) analyzed impacts on travel demand, growth and environmental resources, using a year 2010 planning horizon. The 1991 Bay Crossing Study made preliminary capital cost estimates of the alternatives, ranging from a low of approximately $900 million for Alternative 1 to a high of almost $4 billion for Alternative 6 (all costs in 1990 dollars). Some key findings from the 1991 Bay Crossing Study are:

Planned and programmed improvements at the time (the Baseline), including widening of the San Mateo Bridge and more frequent BART service, would provide enough capacity to accommodate transbay travel to the year 2010, but at high and increasing levels of congestion.
Alternative 4 would carry the greatest number of trips of the five alternatives studied in detail. While peak-hour volumes on the existing San Francisco Bay Bridge would not be reduced, the duration of the peak period would be reduced by over an hour.
Construction of Alternative 4 would have significant land use impacts including displacement of homes and businesses, and destruction of wetlands.
Tunnel options have significant environmental impacts due to dredging. Bay water quality would be impacted and disposal of a very large amount of dredge spoils would have to be addressed.

What is different from the 1991 Study? What new issues/concepts have surfaced?
The 1991 Bay Crossing Study examined the issue of improving transbay travel in a more comprehensive and thorough way than had previously been done. Nevertheless, since 1991, new issues have arisen that suggest re-examination of transbay travel issues may be warranted. A partial list of these issues is as follows:

Updated traffic projections: Recent traffic projections made for an amendment of the 1998 RTP show projected 2010 traffic volumes on the southern transbay bridges to be greater than projected in the 1991 Bay Crossing Study, as shown below:

Bridges

Projected Daily Traffic Volumes for 2010

1991 Bay Crossing Study

Projected Daily Traffic Volumes for 2010

Updated 1998 RTP Analysis

Diff.

SF-Oakland

272,000

319,885

17.6%

San Mateo

75, 000

112,496

50.0%

Dumbarton

62,000

84,429

36.2%

The differences in forecasted traffic volumes are likely due to a number of factors: (1) technical improvements to MTC's travel demand model in the last decade, (2) updated demographic projections indicating higher population growth in the region than previously assumed (see below); and, (3) updated information on current traffic volumes, thus, allowing us to calibrate our travel demand model more accurately against recent actual data.
Projected demographic growth: The 1991 Bay Crossing Study utilized ABAG Projections 1990 demographics (population/employment) as the basis for travel demand modeling. However, updated ABAG projections (Projections 2000) forecast more robust population growth in the region than was assumed by Projections '90 as shown below:

Year 2005

ABAG Projections '90

Year 2005

ABAG Projections 2000

Diff.

Regional Jobs

3,954,160

3,966,990

0.3%

Regional Pop.

6,832,850

7,380,100

8.0%

As a result, conclusions made in the 1991 Bay Crossing Study may need updating given the more rapid growth in regional population than assumed 10 years ago. Intraregional demographic patterns have also shifted. The region is experiencing faster growth in suburban areas such as eastern Contra Costa County and Santa Clara Valley than projected in ABAG Projections '90. For example, Santa Clara County is projected to add 27% of all the projected new jobs in the region between 1995 and 2020.
Operational/system management options: In recent years, more understanding and information is available on how to better operate and manage traffic congestion. New tools are available such as through Traffic Operations Systems (TOS) and Intelligent Transportation Systems (ITS). Recent MTC studies have utilized these tools to develop traffic management approaches for improving congestion and mobility. Such an operational approach was not analyzed in the 1991 Bay Crossing Study. An updated study could better analyze operational and traffic management techniques for improving mobility on the entire southern toll bridge group, and suggest tools for a more systematic traffic management approach.
Land-use impacts: The 1991 Bay Crossing Study did not include an analysis of altering land use patterns and how that might mitigate bridge congestion while improving mobility. An updated study could include a land use "sensitivity" analysis, for example, by simulating the impact of constructing more housing near west bay job centers to reduce the need for transbay commuting.
New rail transit services: While rail options were considered in the 1991 Bay Crossing Study, ACE rail service was not operational or even contemplated at the time, nor were some of the statewide high-speed rail concepts under current consideration. These may be interesting concepts to incorporate into a new Bay Crossing Study.
Expansion of the San Francisco Airport runways: The 1991 Bay Crossing Study looked at a bridge alignment connecting Interstate 380 on the West Bay (just north of the SFO) and I-238 in the East Bay. Since that time, the San Francisco International Airport has been pursuing expansion of its runways in a configuration that could conflict with this bridge alignment. Whether this alignment is viable, or some other alignment would have to be considered, could be addressed in an updated study.
San Francisco-Oakland Bay Bridge Rail Study: While MTC has performed preliminary work on analyzing the feasibility of retrofitting the San Francisco-Oakland Bay Bridge for rail, an updated Bay Crossing Study would be a more appropriate means to help analyze how new transbay facilities (rail and/or auto) may best serve this corridor and impact existing congestion on the San Francisco-Oakland Bay Bridge.
Incorporation of Dumbarton Rail Study: The 1991 Bay Crossing Study did not consider or assume the potential implementation of transit services over the Dumbarton rail bridge. Recent work in this corridor by the Caltrain Joint Powers Board and Dumbarton Corridor Task Force have led to a proposal for initiating rail service over the Dumbarton rail bridge between Union City and the Peninsula. An updated Bay Crossing Study could utilize this information as part of a broader analysis for improving transbay travel for the southern half of the San Francisco Bay.
Longer Range Planning horizon: The planning horizon year assumed in the 1991 Bay Crossing Study was 2010, a short 10 years away. MTC's most recent planning work for the 1998 Regional Transportation Plan (RTP) goes out to year 2020. Given the long lead time needed to actually implement any major transbay transportation improvement, an updated Bay Crossing Study using a 2020 planning horizon would allow us to better link updated conclusions with the 1998 RTP, and give us a more appropriate planning horizon to understand how an improvement may perform when it is actually operational.

An updated Bay Crossing Study could address these issues and others that surface from policy committee discussions or in subsequent public scoping meetings. We anticipate that the geographic scope of the study would be similar to the 1991 Bay Crossing Study, incorporating the entire southern half of the San Francisco Bay from the San Francisco-Oakland Bay Bridge south including the San Mateo and Dumbarton bridges.