This polygon shapefile contains the Census Traffic Analysis Zones (CTAZ) for California for the year 1990. The CTAZ zones range in size from multiple-block level in downtown San Francisco, Oakland, and San Jose to block group and tract level in suburban and rural areas of the region. The CTAZ zones nest within the older, MTC 1099 regional travel analysis zone (RTAZ) system. A traffic analysis zone (TAZ) is a statistical entity delineated by state or local transportation officials for tabulating traffic-related census data-especially journey-to-work and place-of-work statistics. A TAZ usually consists of one or more census blocks, block groups, or census tracts. For the 1990 census, TAZs were defined as part of the Census Transportation Planning Package (CTPP). The U.S. Census Bureau first provided data for TAZs in conjunction with the 1980 census, when it identified them as ''traffic zones.'' Each TAZ is identified by a six-character alphanumeric code that is unique within county or statistically equivalent entity. For the 1990 census, TAZ codes were unique within CTPP area, which generally conformed to a metropolitan area. This layer is part of the Bay Area Metropolitan Transportation Commission (MTC) GIS Maps and Data collection.This dataset is intended for researchers, students, and policy makers for reference and mapping purposes, and may be used for basic applications such as viewing, querying, and map output production, or to provide a basemap to support graphical overlays and analysis with other spatial data.