CA Gov't Code Section 840.6

(a)

A public employee is not liable under subdivision (a) of Section 840.2 for injury caused by a dangerous condition of public property if he establishes that the act or omission that created the condition was reasonable. The reasonableness of the act or omission that created the condition shall be determined by weighing the probability and gravity of potential injury to persons and property foreseeably exposed to the risk of injury against the practicability and cost of taking alternative action that would not create the risk of injury or of protecting against the risk of injury.

(b)

A public employee is not liable under subdivision (b) of Section 840.2 for injury caused by a dangerous condition of public property if he establishes that the action taken to protect against the risk of injury created by the condition or the failure to take such action was reasonable. The reasonableness of the inaction or action shall be determined by taking into consideration the time and opportunity the public employee had to take action and by weighing the probability and gravity of potential injury to persons and property foreseeably exposed to the risk of injury against the practicability and cost of protecting against the risk of such injury.