How have courts interpreted section 830.6(1) of the California Highway Code of Civil Procedure when determining whether a defendant is immune from liability under the California Motor Vehicle Act?

At the risk of jumping over the duty horse into the immunity cart (see Williams v. State of California (1983) 34 Cal.3d 18, 22, 192 Cal.Rptr. 233, 664 P.2d 137), we shall assume for purposes of argument there exists a triable issue of fact whether defendant's duty to prevent accidents caused by dangerous conditions on public property was breached by the design of the subject intersection. Because the trial court ruled that defendant was immune pursuant to section 830.6, and because we find that issue dispositive, we need consider only that ruling.