Outdoor advertising in Santa Clara County must follow Caltrans brightness rules adopted from the federal Highway Beautification Act. Digital displays cannot exceed 0.3 footcandles over ambient at the regulated measurement distance and must dim automatically at night.
Billboard illumination on freeways and primary highways in Santa Clara County is governed by the California Outdoor Advertising Act and Caltrans regulations consistent with the federal Highway Beautification Act (HACA). Digital and lighted signs must include automatic dimming photocells, limit changes to no more than once every four seconds, and not exceed 0.3 footcandles over ambient measured at a defined distance from the sign face. Light spill onto adjacent residential properties triggers additional review under SCC Title C outdoor-lighting standards, which require shielded fixtures and full cutoff for any sign over six feet tall in or adjacent to residential zones. Daytime brightness levels are also capped to prevent driver glare.
Operating a billboard above the brightness cap or without functioning dimming controls allows Caltrans to suspend the Outdoor Advertising permit. The County can also issue daily nuisance abatement penalties for light trespass complaints from neighboring residents.
See how Palo Alto's billboard lighting rules stack up against other locations.
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