As the last element of a design immunity defense under Gov. Code 830.6, the government entity must establish the reasonableness of its design.  But to do so, it bears only a slight burden of proving that there was substantial evidence to support the reasonableness of the design.  So long as the government entity produces some substantial evidence of reasonableness, such as an expert opinion, it does not matter that the plaintiff’s expert or others disagree.  Here, the government entity produced both an expert opinion and other evidence of reasonableness of design, so it was rightly granted summary judgment.  Also, plaintiff failed to raise a triable issue of fact as to whether the highway exit as actually built did not substantially conform to the reasonable plans for its construction.  Her expert witness offered only inadmissible speculation not opinions supported by facts.  Also placing an exist sign within feet of its planned location was substantial compliance with the plans.