California Code, Vehicle Code - VEH § 2454

(a) The authority for incident command at the scene of an on-highway hazardous substance incident is vested in the appropriate law enforcement agency having primary traffic investigative authority on the highway where the incident occurs. Responsibility for incident command at the scene of an on-highway hazardous substance incident shall continue until all emergency operations at the scene have been completed and order has been restored.

(b) Notwithstanding subdivision (a), the local governing body of a city, whether general law or chartered, which has jurisdiction over the location where an on-highway hazardous substance incident occurs may assign the authority for incident command at the scene of an on-highway hazardous substance incident on local streets and roads, other than freeways, to either the local law enforcement agency or the local fire protection agency. However, the department is responsible for incident command at the scene of an on-highway hazardous substance incident on all highways where the department has primary traffic investigative authority. Any law enforcement agency having primary traffic investigative authority may enter into written agreements with other public agencies to facilitate incident command at the scene of an on-highway hazardous substance incident on local streets and roads other than freeways.

(c) For purposes of this section, “incident command at the scene of an on-highway hazardous substance incident” means coordination of operations which occur at the location of a hazardous substance incident. This coordinating function does not include how the specialized functions provided by the various other responding agencies are to be performed. The incident commander at the scene of an on-highway hazardous substance incident shall consult with other response agencies at the scene to ensure that all appropriate resources are properly utilized, and shall perform his or her coordinating function in a manner designed to minimize the risk of death or injury to other persons.