It is an association of local county governments, with policy makers consisting of mayors, councilmembers, and county supervisors, and also has capital planning and fare setting powers for the county's transit systems, the San Diego Metropolitan Transit System (MTS) and the North County Transit District (NCTD), some of which was assumed by the Metropolitan Transit Development Board (became MTS in 1986).

The approval of a project required the majority tally vote representing all cities and board members and the majority of represented members weighted by population.

[1] From 2018 to 2023, the director of SANDAG was Hasan Ikhrata, who made transit expansion and roadway pricing a priority.

[3] The Compass Card was launched by SANDAG in May of 2009 to integrate the fare payment systems of San Diego MTS and North County Transit District into one system, meant to reduce the number of fare transactions at customer service centers.

Those include:[4] Additionally, 11 other agencies/governments that border San Diego County or are relevant to the region also participate in the Association as advisory members.