SB 743: Changing How We Analyze Traffic Impacts 

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Update Regarding Transportation Study Guide

On June 24, 2020, the Board of Supervisors (Board) approved thresholds for land development projects within the County to meet new California Environmental Quality Act (CEQA) requirements under Senate Bill 743 (SB 743) for Vehicle Miles Traveled (VMT). Under SB 743, CEQA analysis can no longer use road congestion or the amount of time a driver is delayed on the road – commonly measured by level of service (LOS) – when analyzing transportation impacts. Therefore, instead of using LOS, a project's environmental impacts must be evaluated by the amount and distance people drive to destinations.

On May 19, 2021, the Board received an overview of the options as part of the County’s implementation of SB 743 and adoption of its TSG for VMT, including the geographic boundary to calculate average VMT (unincorporated, regional, and sub-regional), the significance threshold used to evaluate projects (15% below the average VMT), establishing the criteria for which projects must prepare a VMT analysis (110 Average Daily Trips), and whether to establish a Local Mobility Analysis. On September 15, 2021, the Board adopted a resolution to rescind the previously adopted Transportation Study Guide dated June 2020 including the Transportation California Environmental Quality Act (CEQA) threshold of significance for VMT. The Board also directed staff to return to the Board in January 2022 with additional information on the 13 subject matter areas or items related to VMT that the board directed staff to analyze on May 19, 2021. To view the Board Letter associated with the September 15th Item, please Click Here

The Board provided direction to explore 13 items related to VMT:

  1. Assess and explore the process by which infill development can be done in a manner to ensure no VMT mitigation is necessary.
  2. Explore the potential creation of transit accessible areas and look at the intersection between VMT efficient areas or lower thresholds in accordance with the areas that do not require further analysis. Explore the potential transit corridors and look at the SANDAG Regional Transportation Plan, Metropolitan Transit System (MTS), North County Transit District (NCTD), and other possible areas and how that may impact VMT efficient areas or areas covered by the exemption.
  3. Explore programmatic or plan-level mitigation opportunities for VMT, including the concept of a regional mitigation bank.
  4. By-right process for development in VMT efficient areas.
  5. Further exploration of exceptions to the VMT thresholds for affordable housing projects at less than 100% affordable, including mixed income and various components of Area Median Income (AMI), along with exploring the possibility of exceptions for middle income or workforce housing, local hire, and agriculture type projects that might have a net impact of lowering VMT.
  6. Explore land use density of land that is in VMT efficient areas.
  7. Continue to track guidance from the California Office of Planning and Research (OPR), along with other governing body efforts, including the SANDAG Regional Transportation Plan.
  8. Monitor the progress of other jurisdictions as it relates to their adoption, along with what unique programs, exemptions, or opportunities they may be exploring that the County may want to consider.
  9. Consider a phase-in timeline to allow for a transition into a regional geography.
  10. Consider compliance options for projects that have already been proposed or are in the process now.
  11. Conduct an analysis of the options to remove the Local Mobility Analysis.
  12. Inform the Board regarding updates on development of the Smart Growth component of the Climate Action Plan (CAP) SEIR to ensure it is integrated and aligned with efforts around VMT.
  13. Conduct an analysis of proposed housing projects designated for individuals under 60% AMI and under 80% AMI and the potential cost impact of switching to a regional geography.

County staff is currently analyzing the 13 items directed by the Board related to the implementation of SB 743 and VMT in the unincorporated County. The following technical memorandums have been prepared in response to 4 of the items, including opportunities for infill development (item 1), creating transit accessible areas (item 2), VMT mitigation program options (item 3), and affordable housing (item 5). The information in these memos will inform the options for the Board’s consideration on January 26, 2022.   

Item 1 - Infill Development in San Diego County Technical Memorandum

Item 2 - Transit Expansion Memorandum

Item 3 - VMT Mitigation Program Memorandum

Item 5 - Affordable Housing Memorandum (In-process)

Planning & Development services staff is also seeking stakeholder input as we develop the options and information in response to the Board’s 13 items. Please contact us with the email/phone number provided below, subscribe to our Stakeholder E-mail List, and check back to this project website to learn more about updates to the TSG as a result of the September 15, 2021 Board meeting.


With the adoption of Senate Bill (SB) 743, the State of California changed the method of traffic analysis required through the California Environmental Quality Act (CEQA) for publicly- and privately-initiated projects.  The law changed the way local jurisdictions, like the County of San Diego (County), analyze transportation impacts from development projects and identify mitigation measures to reduce those impacts. SB 743 became effective on July 1, 2020.

The previous practice of evaluating traffic transportation impacts used on-road congestion or level of service (LOS).  SB 743 requires the amount of driving and length of trips – as measured by "vehicle miles traveled" or VMT – be used to assess transportation impacts on the environment for CEQA review. These impacts will be reduced or “mitigated” by options such as increasing transit, providing for active transportation such as walking and biking, and participating in mitigation banks. All jurisdictions have the option to tailor requirements to their unique communities. 

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