California law strictly limits the use of emergency vehicle lights to active emergencies, pursuits, or fire responses. Under Vehicle Code § 21055, lights and sirens may only be used when responding to specific urgent situations, not for patrol or display. Sections § 25250 and § 25269 further prohibit flashing red lights unless these strict conditions are met. Unauthorized use is not only unlawful—it may constitute impersonation or abuse of authority under Penal Code § 538d. This framework ensures emergency lights are used only when public safety is genuinely at risk.