How have the courts treated improvements made to the natural condition of the sand dunes in a vehicular recreation area?

Here, there was no evidence of any alteration in the natural condition of the dunes in the vehicular recreation area. It was undisputed that respondent had not conducted any improvement work in the dunes area. None of the "improvements" urged by appellant to remove the immunity--signs setting speed limits, warning of surf conditions and marking access roads, and fences and signs prohibiting entry into environmentally sensitive or nonpublic areas--were erected within or near the dunes area. The dunes were not therefore transformed into improved property. Further, there was no evidence even suggesting that these so-called improvements had any causal connection with appellant's accident. (See Eben v. State of California, supra, 130 Cal.App.3d at 423, 425, 181 Cal.Rptr. 714.)