SB 743: Changing How We Analyze Traffic Impacts 

To sign up for e-mail updates on this effort, please click here.


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. 

Bus Stop

Transportation Study Guide

On June 24, 2020, the Board of Supervisors approved the Transportation Study Guide (TSG) which includes the process and procedures for project applicants and their consultants to use when preparing transportation analysis in the unincorporated area. The TSG includes four chapters:

  1. Introduction
  2. Transportation Study Initiation (screening criteria, scoping agreement, and submittal instructions)
  3. CEQA Requirements for Transportation VMT (CEQA VMT analyses and potential mitigations)
  4. Local Mobility Analysis (non-CEQA analyses and potential improvements)

VMT Efficient Area Map Viewer

The County has developed an Interactive Map Viewer as an additional tool in analyzing VMT for the unincorporated area. The viewer includes information that has two primary uses in the context of the TSG:

  1. Indicates if a project is located in a “VMT efficient” area of the unincorporated area – meaning it is at least 15% below the unincorporated county average – and therefore likely “screened out” from further VMT analysis. The "VMT efficient" areas generally occur along the western edge of the unincorporated county (near the cities) and in county villages (e.g. Alpine, Ramona, Fallbrook) where residents are closer to shopping, employment, and entertainment destinations.
  2. Provides a project’s VMT/Resident, VMT/Employee, or VMT/Service Population (for projects that have an estimated 2,400 or less driveway average daily trips).

Please see sections 3.3.1: Screening Criteria for CEQA VMT Analysis and 3.3.3: VMT Analysis Procedures in the TSG for additional information on the use of the information displayed in the map viewer. Static versions of these maps, organized by VMT metric (e.g. VMT/Resident, VMT/Employee, VMT/Service Population), can also be found in Appendix C of the TSG.

The map viewer contains multiple layers that can be turned on/off in the navigation pane on the right side of the map viewer. Please note, if multiple layers are turned “on” at the same time, the map viewer will display whichever layer is farther to the top of the navigation pane.

For each map by VMT metric, you will see three color intensities:

  • Light color (above the average VMT): This means that projects in this area are likely to have a significant VMT impact and are unlikely to fully mitigate that impact.
  • Medium color (between 0% - 15% below the average VMT): This means that projects in this area are likely to have a significant VMT impact, but one that could potentially be mitigated with VMT reducing measures down to 85% of the regional average or lower.
  • Darkest color (at least 15% below the average VMT): This means that projects in this area will likely be considered as having a less than significant VMT impact and will not have to conduct further VMT analysis.
  • The maps also include a gray color, which represents areas with insufficient data to determine average VMT (i.e., not enough existing residents or employees). For project locations in these areas, projects must conduct a SANDAG regional travel demand model run to determine project VMT (if not eligible for screening under a different screening criteria).
  • NOTE: The VMT Efficient Area Screening Maps must be considered in the context of the full TSG. The "likely" and "unlikely" language above reflects generalized outcomes for many, but not all, projects related to screening, VMT impacts, and VMT mitigation. 

We Want to Hear from You

The County is currently moving forward with Phase II of SB 743 implementation, which will present additional options to the Board of Supervisors related to VMT mitigations. The County is committed to providing multiple ways to contribute input, even as we face the challenge of COVID-19. 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 about Phase II engagement opportunities as they become available.

For More Information:

Please contact:


Phone: (858) 505-6677