What is the effect of section 21055 and section 21056 of the California Vehicle Code on emergency vehicles?

"The effect of Vehicle Code sections 21055 and 21056 is: where the driver of an authorized emergency vehicle is engaged in a specified emergency function he may violate certain rules of the road, such as speed and right of way laws, if he activates his red light and where necessary his siren in order to alert other users of the road to the situation. In such circumstances the driver may not be held to be negligent solely upon the violation of specified rules of the road, but may be held to be negligent if he fails to exercise due regard for the safety of others under the circumstances. [Citation.]" (City of Sacramento v. Superior Court (1982) 131 Cal.App.3d 395, 402-403.)