RCW 47.01.170

The department or its duly authorized and acting assistants, agents, or appointees have the right to enter upon any land, real estate, or premises in this state, whether public or private, for purposes of making examinations, locations, surveys, and appraisals for highway purposes. The making of any such entry for those purposes does not constitute any trespass by the department or by its duly authorized and acting assistants, agents, or appointees.