The Transportation Authority of Marin (TAM) is designated as both the congestion management agency and the transportation sales tax authority for Marin County. As the Congestion Management Agency (CMA), TAM addresses Marin's unique transportation issues, fulfilling the legislative requirements of Propositions 111 and 116, approved in June 1990. TAM was designated the sales tax authority in 2004, for the purpose of administering the 1/2 cent transportation sales tax in Marin County, passed by voters in November 2004 as Measure A.
The Authority is responsible for managing a variety of transportation projects and programs in Marin County, receiving federal, state, regional, and local funds, working closely with all eleven cities and towns as well as the county. The TAM Board includes representatives from each of the cities and towns in Marin County, plus the five members of the Board of Supervisors. The TAM Board meets monthly and operates under a variety of committees.