Is there a design immunity defense in the context of liability for injuries caused by the design of a construction of or improvement to public property?

However, statutory law provides a "design immunity" defense to such liability. ( 830.6.)⁷ Under section 830.6 there is no liability for an injury caused by the plan or design of a construction of or improvement to public property where such plan or design has been approved in advance of the construction or improvement by the legislative or other authorized body of the public entity provided the trial or appellate court determines that there is any substantial evidence that a reasonable legislative (or other authorized) body or public employee could have adopted or approved the plan or the design or standards therefor. Thus, a public entity raising a design immunity defense must establish three elements: (1) a causal relationship between the plan or design and the accident, (2) discretionary approval of the plan or design prior to construction and (3) the existence of substantial evidence supporting the reasonableness of the adoption of the plan or design. (Higgins v. State of California (1997) 54 Cal.App.4th 177, 185.)