While we strive to use plain language, acronyms and jargon invariably will creep into many discussions about regional planning issues. For this we apologize and offer a glossary of selected acronyms and terms.



A collective term for the many measures taken to address the impacts of climate change. In Plan Bay Area 2050, adaptation approaches describe a number of different ways the Bay Area can address sea level rise through restoring marshes, constructing levees, raising infrastructure or retreating from the shoreline. See also: Climate Change.

Assembly Bill 32 (AB 32)

AB 32 (Nuñez, Statutes of 2006), known also as the California Global Warming Solutions Act of 2006, requires a statewide reduction in greenhouse gas emissions to 1990 levels or lower by the year 2020.

Assembly Bill 617 (AB 617)

AB 617 (C. Garcia, Statutes of 2017) is a state mandate to improve community health and promote equity by reducing exposure to air pollutants in neighborhoods most affected by air pollution.

Assembly Bill 1487 (AB 1487)

AB 1487 (Mullin, Statutes of 2019) is the legislation that established BAHFA. See also: Bay Area Housing Finance Authority (BAHFA).

The Association of Bay Area Governments (ABAG)

ABAG is the official Council of Governments and regional land use planning agency representing the San Francisco Bay Area's nine counties and 101 cities and towns. Formed in 1961, ABAG provides research and analysis, financial services and other cost-effective local government service programs. ABAG also builds partnerships to address regional economic, social and environmental challenges.

Bay Area Housing Finance Authority (BAHFA)

A shared initiative of MTC and ABAG, in partnership with cities and counties, to step up efforts to address the Bay Area’s housing affordability challenges. BAHFA establishes the authority to generate revenues to fund affordable housing through a regional revenue ballot measure.

Bay Area

The counties of Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano and Sonoma together as a region.


“Blueprint” refers to the “first draft” of the regional plan.

The Draft Plan Bay Area 2050+ Blueprint process has begun, and will continue through December 2023. At that time, work on the Final Plan Bay Area 2050+ Blueprint will begin.

The Plan Bay Area 2050 Blueprint was the “first draft” of Plan Bay Area 2050, the current long-range regional plan. The Final Blueprint was approved by MTC and the ABAG Executive Board in fall 2020 and winter 2021.

Building Retrofit

Measures taken or equipment used to improve the quality and safety of existing buildings that were built before modern codes. Retrofits can be done to improve performance in fire or seismic conditions, or to improve water or energy efficiency.

Carbon Neutrality

A balance between carbon emissions and carbon neutrality, such that the level of carbon in the atmosphere is static rather than increasing, in order to mitigate climate change. Actions to achieve carbon neutrality include measures that reduce greenhouse gas emissions as well as measures that absorb carbon, like maintaining healthy forests and marshes. See also: Decarbonization, Greenhouse Gases, Climate Change.

California Environmental Quality Act (CEQA)

This statute requires state and local agencies to identify the significant environmental impacts of their actions and to avoid or mitigate those impacts, if feasible.

California Department of Housing and Community Development (HCD)

HCD is a state agency that develops housing policy, building codes and regulations and administers housing finance, economic development and community development programs. HCD determines the total number of new homes the Bay Area needs to build, and how affordable those homes need to be, through the Regional Housing Needs Allocation (RHNA) process.

Call for Projects

Regional agencies use this procedure to solicit competing bids from counties, cities, transit agencies, community-based organizations and other stakeholders for projects to be funded as part of long-range plans.

Climate Change

Climate change refers to changes in the Earth’s weather patterns, including the rise in average temperature due to an increase in heat-trapping of greenhouse gases (GHGs) in the atmosphere. Climate scientists agree that climate change is a man-made problem caused by the burning of fossil fuels like petroleum and coal. Transportation accounts for about 40% of the Bay Area’s GHG emissions. Climate change is expected to significantly affect the Bay Area’s public health, air quality and transportation infrastructure through sea level rise and extreme weather. See also: Greenhouse Gases (GHGs).


A process in which transportation plans and spending programs are reviewed to ensure they are consistent with federal clean air requirements; transportation projects collectively must not worsen air quality.

Communities of Concern

See Equity Priority Communities.

Council of Governments (COG)

A COG is a voluntary, regional organization with state- and locally defined boundaries that delivers a variety of federal, state and local programs. COGs function as planning organizations and technical assistance providers to their member local governments. As such, they are accountable to local governments and effective partners for state and federal governments. ABAG is the COG for the nine-county San Francisco Bay Area.

County Transportation Agencies (CTAs)

Formerly called Congestion Management Agencies (CMAs), CTAs are county-level organizations responsible for preparing and implementing congestion management programs. CTAs also are responsible for overseeing and delivering transportation sales tax measures that voters have approved.


The removal of greenhouse gas emissions from products and systems that currently rely on carbon sources. While decarbonization includes strategies that reduce emissions, it focuses more on switching out fuel and energy sources with emissions — like natural gas or petroleum — for renewably generated electricity. See also: Greenhouse Gases, Climate Change, Carbon Neutrality.

Deed-Restricted Affordable Housing

Homes for which rents are set at a price less than one-third of the gross monthly income of households earning a maximum percentage of the area median income. These restrictions are established through a deed on the property. While the maximum eligible income level varies by property, typical maximum eligible income is 80% of the area median income, taking into account household size.

Environmental Impact Report (EIR)

The California Environmental Quality Act (CEQA) requires that an EIR be prepared if there is substantial evidence that a project may have a significant effect on the environment. A draft EIR shall be included as part of the review and approval process whenever a public hearing is held on the project. Following adoption of a final EIR, the lead agency makes a decision whether to proceed with the project.

Environmental Justice

This term stems from a Presidential Executive Order to promote equity for disadvantaged communities and promote the inclusion of racial and ethnic populations and low-income communities in decision-making. Local and regional transportation agencies must ensure that services and benefits, as well as burdens, are fairly distributed to avoid discrimination.


At MTC and ABAG, equity means just inclusion into a Bay Area where everyone can participate, prosper and reach their full potential. A racial justice focus is acted upon by directing resources to historically underserved, systemically marginalized communities (including low-income communities and communities of color) at a scale to meaningfully reverse the disparities that diminish access in the nine-county Bay Area.

Equity Analysis

Consistent with federal requirements for environmental justice, MTC and ABAG will conduct an equity analysis covering Plan Bay Area to determine how the benefits and burdens of the plan’s investment strategy affect minority and low-income communities.

Equity Priority Communities

Formerly known as Communities of Concern, Equity Priority Communities are geographic areas (census tracts) that have a concentration of both residents of color and residents with low incomes, or that have a concentration of residents with low incomes and any three or more of the following six factors:

  • People with limited English proficiency,
  • Zero-vehicle households,
  • Seniors aged 75 years and over,
  • People with one or more disability,
  • Single-parent families, and
  • Renters spending more than 50% of their household income on housing.

Financial Constraint

A federal requirement that long-range transportation plans include only projects that have a reasonable expectation of being funded, based upon anticipated revenues. In other words, long-range transportation plans cannot be pie-in-the-sky wish lists of projects. They must reflect realistic assumptions about revenues that will likely be available looking forward at least 20 years.

Futures Planning

In the development of Plan Bay Area 2050, "Futures Planning" was a new way of looking at long-range planning. It focused on exploring divergent what-if scenarios to identify strategies that are effective in a wide variety of circumstances. It replaced traditional scenario planning, where funding and growth are distributed based on fixed assumptions; instead, the Futures process outlined a variety of potential political, technological, economic and environmental challenges that would impact the future lives of Bay Area residents.

Global Warming

See Climate Change.

Greenhouse Gases

Any of the gases — including carbon dioxide, methane and ozone — whose absorption of solar radiation is responsible for the greenhouse effect, in which the atmosphere allows incoming sunlight to pass through but absorbs heat radiated back from the earth’s surface. Greenhouse gases act like a heat-trapping blanket in the atmosphere, causing climate change.

Growth Geographies

Areas within the Bay Area’s nine counties where future housing and/or job growth would be focused under the plan’s strategies over the next 30 years. These geographies are identified for growth either by local jurisdictions or because of their proximity to transit or opportunities like well-resourced schools or easy access to jobs. Areas within unmitigated high hazard zones for wildfire and sea level rise cannot be designated as Growth Geographies. The four growth geographies used in Plan Bay Area 2050 are High-Resource Areas (HRAs), Priority Development Areas (PDAs), Priority Production Areas (PPAs) and Transit-Rich Areas (TRAs).

Guiding Principles

Five guiding principles that informed and guided the development of Plan Bay Area 2050: affordable, connected, diverse, healthy and vibrant. These principles were distilled from the thousands of comments received at online and in-person events, and they are used to evaluate the plan’s outcomes.

High-Resource Areas (HRAs)

State-identified places (using a subset of the high-opportunity areas identified by the California Department of Housing and Community Development) with well-resourced schools and access to jobs and open space, among other advantages. This designation only includes places that meet a baseline transit service threshold of bus service with peak headways of 30 minutes or better, when located in jurisdictions that have not nominated at least 50% of their PDA-eligible lands. See also: Growth Geographies.


The Horizon initiative was an 18-month, foundational part of the planning process leading up to Plan Bay Area 2050. It was the first comprehensive Bay Area planning effort to look not just at transportation and housing but also economic development, climate resilience and the effects of emerging technologies.

See also: Futures Planning, Guiding Principles.

Land Use Model

Used by researchers and planners to identify expected population, jobs and housing growth, and to understand the interactions between land use, transportation, and the economy. Models help planners analyze and test various spatial distributions of jobs, population and land uses and describe to policy-makers and the public about the relationship between land use and transportation.

Metropolitan Planning Organization (MPO)

A federally required planning body responsible for the transportation planning and project selection in its region; the governor designates an MPO in every urbanized area with a population of over 50,000. MTC is the MPO for the nine-county San Francisco Bay Area.

Metropolitan Transportation Commission (MTC)

The transportation planning, financing and coordinating agency for the nine counties of the San Francisco Bay Area, MTC serves as the Bay Area’s MPO and Regional Transportation Planning Agency (RTPA) as designated by the state. Created by the state legislature in 1970, MTC regularly updates the region’s long-range plan, a comprehensive blueprint for the development of transportation facilities in the region. MTC also manages a variety of operational programs, such as FasTrak®, Clipper® and the 511 traveler information system.

Priority Conservation Areas (PCAs)

Regionally significant open spaces for which there exists a broad consensus for long-term protection and for which public funds may be invested to promote their protection. See also: Growth Geographies.

Priority Development Areas (PDAs)

Locally and voluntarily identified locations within existing communities that present infill development opportunities, and are easily accessible to transit, jobs, shopping and services. See also: Growth Geographies.

Priority Production Areas (PPAs)

Locally identified places for job growth in middle-wage industries like manufacturing, logistics or other trades. An area must be zoned for industrial use or have a predominantly industrial use to be a PPA. See also: Growth Geographies.

Plan Bay Area (2013)

Adopted in 2013, Plan Bay Area was the Bay Area’s first regional transportation plan to incorporate a state-mandated Sustainable Communities Strategy. It was also the first regional plan to be a joint effort led by MTC and ABAG.

Plan Bay Area 2040 (2017)

The strategic update to Plan Bay Area (2013), built on earlier work to develop an efficient transportation network, provide more housing choices, and grow in a financially and environmentally responsible way. Plan Bay Area 2040 was adopted in 2017.

Plan Bay Area 2050 (2021)

A long-range plan charting the course for the future of the nine-county San Francisco Bay Area. Plan Bay Area 2050 focuses on four key elements — housing, the economy, transportation and the environment — and identifies a path to make the Bay Area more equitable for all residents and more resilient in the face of unexpected challenges. The Metropolitan Transportation Commission and the Association of Bay Area Governments adopted Plan Bay Area 2050 in October 2021.

Plan Bay Area 2050+

This is a limited and focused update to Plan Bay Area 2050, the current long-range regional plan for the Bay Area. Work is underway on Plan Bay Area 2050+, with an anticipated adoption in fall 2025.

Regional Advisory Working Group (RAWG)

An advisory group originally set up to advise staff on development of Plan Bay Area. Its membership includes staff representatives of local jurisdictions (CTAs, planning directors, transit operators, public works agencies) as well as representatives from the business, housing, environmental and social-justice communities.

Regional Equity Working Group (REWG)

REWG was set up to advise MTC and ABAG staff in developing an equity analysis related to communities of color and communities with low incomes for Plan Bay Area. See also: Equity Analysis.

Regional Housing Needs Allocation (RHNA)

RHNA is a state mandate that all California cities, towns and counties must plan for the housing needs of residents at all income levels. The California Department of Housing and Community Development (HCD) determines the total number of new homes the Bay Area needs to build, and how affordable those homes need to be. ABAG then distributes a share of the region’s housing need to each city, town and county in the region. Each local government must then update the Housing Element of its general plan to show the locations where housing can be built and the policies and strategies necessary to meet the community’s housing needs. RHNA and Plan Bay Area plan for housing on two separate time horizons: RHNA focuses on the shorter-term with an eight-year focus, while Plan Bay Area presents a longer-term vision for housing over the next several decades.

Regional Network Management (RNM)

RNM looks at the entire transit system as a whole, including fares, schedules, network connectivity, operations, budgets and more. MTC is working to identify ways to improve the network and rider experience.

Regional Transportation Plan (RTP)

A master plan to guide the region’s transportation investments for a period of at least 20 years. Updated every four years, it is based on projections of growth in population and jobs and the ensuing travel demand. Required by state and federal law, it includes programs to better maintain, operate and expand transportation. Plan Bay Area 2050 serves as the region’s current RTP.

Regional Transportation Planning Agency (RTPA)

A county or multi-county entity charged to meet state transportation planning and programming requirements, created by state statute in 1972 with the passage of AB 69 (Deddeh, Statutes of 1972). MTC serves as the Bay Area’s RTPA for the nine-county Bay Area.

Senate Bill 375 (SB 375)

Senate Bill 375 (Steinberg, Statutes of 2008) became law in 2008 and requires RTPAs to develop a Sustainable Communities Strategy (SCS). It includes two additional key statutory requirements and a host of voluntary measures. It is designed to complement AB 32. The first requirement is to reduce per-capita carbon dioxide (CO₂) emissions from cars and light-duty trucks, primarily by building more compact communities with better access to mass transit and other amenities, so people have more transportation choices and do not have to drive as much. The second requirement is to house 100% of the region’s projected population growth, for people at all income levels.

Senate Bill 743 (SB 743)

SB 743 (Steinberg, Statutes of 2013), implemented across the state in 2020, represents a rethinking of the transportation impacts of development. Historically, California environmental review has evaluated the transportation impacts of new developments based on their forecasted change in traffic congestion as measured by level of service. SB 743 updates the environmental review process to focus instead on the amount of new driving — as measured by vehicle miles traveled — that development incentivizes.


In the Plan Bay Area 2050 context, a strategy is a public policy or set of investments that can be implemented in the Bay Area at the city, county, regional or state level over the next 30 years. A strategy is not a near-term action, a mandate for a jurisdiction or agency, or a legislative proposal.

Structural Hardening

A suite of measures to decrease the likelihood of building damage in wildfire conditions. Common measures to harden structures include the materials used for roofing, siding and windows, as well as the design of vents, openings and decks.

Sustainable Communities Strategy

An integrated land use and transportation plan that all metropolitan regions in California must complete under Senate Bill 375. In the San Francisco Bay Area, this integration includes ABAG’s Projections and Regional Housing Needs Allocation (RHNA) and MTC’s Regional Transportation Plan (RTP). Plan Bay Area 2050 will serve as the region’s next SCS.

Transit 2050+

Transit 2050+ is the transportation element within Plan Bay Area 2050+. As the Bay Area continues to face financial challenges from the COVID-19 pandemic, Transit 2050+ will focus on prioritizing revisions to the six transit-related strategies from the current long-range transportation plan, Plan Bay Area 2050.

Transit-Oriented Communities (TOC) Policy

Building on previously identified Transit-Rich Areas, MTC’s 2022 TOC Policy promotes housing and commercial development near transit stations.

Transit-Rich Areas (TRAs)

Areas near rail, ferry or frequent bus service that were not already identified as PDAs, in jurisdictions that have not nominated at least 50% of their PDA-eligible lands. Specifically, these are areas within 1/2 mile of either an existing rail station or ferry terminal (with bus or rail service), a bus stop with peak service frequency of 15 minutes or less, or a planned rail station or planned ferry terminal (with bus or rail service). See also: Growth Geographies, Transit-Oriented Communities (TOC) Policy.

Transportation Demand Management (TDM)

A collective term for the many different approaches to make it easier for individuals to shift behavior away from driving alone and promote less overall driving and traffic on roads.

Travel Model

Used by researchers and planners for simulating current travel conditions and for forecasting future travel patterns and conditions. Models help planners and policymakers analyze the effectiveness and efficiency of alternative transportation investments in terms of performance, such as mobility, accessibility, environmental and equity impacts.

Vision Zero

An internationally adopted framework that seeks to eliminate all traffic fatalities and severe injuries while increasing safe, healthy and equitable mobility for all.


Development standards established by local governments defining the type, intensity and form of permitted development on parcels within the jurisdiction. Examples of zoning include maximum building heights, floor area ratios, and permitted dwelling units per acre.