What is design immunity for a plaintiff in a motor vehicle accident?

The rationale behind design immunity is to prevent a jury from reweighing the same factors considered by the governmental entity which approved the design. "[T]o permit reexamination in tort litigation of particular discretionary decisions where reasonable men may differ as to how the discretion should be exercised would create too great a danger of impolitic interference with the freedom of decision-making by those public officials in whom the function of making such decisions has been vested." (4 Cal. Law Revision Com. Rep. (1963) p. 823, quoted in Cameron v. State of California [208 Cal.App.3d 867] (1972) 7 Cal.3d 318, 326, 102 Cal.Rptr. 305, 497 P.2d 777.) Three elements must be established to claim the defense: (1) a causal relationship between the plan and the accident, (2) discretionary approval of the plan prior to construction, and (3) substantial evidence supporting the reasonableness of the design. (Ramirez v. City of Redondo Beach (1987) 192 Cal.App.3d 515, 523, 237 Cal.Rptr.

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