(a) It is unlawful for a driver of a vehicle to fail to obey a sign or signal defined as regulatory in the federal Manual on Uniform Traffic Control Devices, or a Department of Transportation approved supplement to that manual of a regulatory nature erected or maintained to enhance traffic safety and operations or to indicate and carry out the provisions of this code or a local traffic ordinance or resolution adopted pursuant to a local traffic ordinance, or to fail to obey a device erected or maintained by lawful authority of a public body or official.
(b) Subdivision (a) does not apply to acts constituting violations under Chapter 9 (commencing with Section 22500) of this division or to acts constituting violations of a local traffic ordinance adopted pursuant to Chapter 9 (commencing with Section 22500).