The Federal Highway Administration (FHWA) publishes the Manual of Uniform Traffic Control Devices (MUTCD), which contains national design, application, and placement standards, guidance, options, and support provisions for traffic control devices. The purpose of the MUTCD is to provide uniformity of these devices, which include signs, signals, and pavement markings, to promote highway safety and efficiency on the Nation’s streets and highways. When a new edition or revision of the national MUTCD is issued, States have two years to adopt it, with or without a State supplement, or to adopt a State MUTCD that is in substantial conformance with the new edition of the National MUTCD.
The state of California adopts its own MUTCD, the CA MUTCD, with each new National MUTCD release or update. The current CA MUTCD can be viewed here: https://dot.ca.gov/programs/traffic-operations/camutcd