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.

The San Diego Board of Supervisors adopted the Transportation Study Guide (TSG) which included the infill screening criteria on Sept 28, 2022. The TSG can be found here:

https://www.sandiegocounty.gov/content/sdc/pds/SB743.html

SB 743 includes the following two legislative intent statements:

• Ensure that the environmental impacts of traffic, such as noise, air pollution, and safety concerns continue to be properly addressed and mitigated through the California Environmental Quality Act.

• More appropriately balance the needs of congestion management with statewide goals related to infill development, promotion of public health through active transportation, and reduction of GHG emissions.

Based on definitions and information provided by both the US Census and Department of Transportation, the following criteria was prepared to define and map infill in the unincorporated area:

1. Household density. Household density above 425 housing units per square mile was selected based on the US Census definition for urban area, replacing the previous use of population to account for smaller household sizes and seasonal populations. The 425 housing units per square mile is used by the Census Bureau to identify urban areas across the country based on the concentration of housing.

2. Intersection density. An urban area is defined by having over 128 intersections per square mile.

3. Jobs Accessibility. Jobs accessibility is determined by the number of employment opportunities within a 15-mile radius of a location, which is the average driving distance to work based on information from the US Department of Transportation.

Using the above criteria creates a geographic area that is associated with urban development within the unincorporated area of the county. Development in more dense areas with high job accessibility leads to more diversity in land use, demand for transit (bus and trolley) and multimodal infrastructure (walking and biking), and shorter vehicle trips, which reduce greenhouse gasses and VMT

VMT Infill layer was updated on 07/30/2024. Village BOS TAZ's were clipped to Village Boundaries to match was adopted in the 09/2022 VMT Infill maps.