The RTPA_2013 polygon feature class provides California Regional Transportation Planning Agencies (RTPA) legislative boundaries, primarily for regional planning applications.

The list of California Transportation Planning Agencies is current as of February, 2014, provided by Division of Transportation Planning, Office of Regional and Interagency Planning.With the exception of Tahoe Regional Planning Agency (TRPA*), all of the RTPA boundaries follow county boundaries, some RTPA are multi-county. This feature class was created primarily based on 2010 Census county lines exclude the islands.

*TRPA is actually a bi-state agency created by the U.S. Congress and a compact between California and Nevada. Federal laws and California and Nevada statutes govern it. TRPA is composed of parts of two counties in California, El Dorado and Placer, and two counties in Nevada. The portions of two California counties outside the Tahoe basin are part of the Sacramento Area Council of Governments (SACOG).

Reference: CALCOG GUIDE TO REGIONAL PLANNING, AS REVISED BY SB 375 JANUARY 2009.