We are developing the Robotic Travel Aid, the primary function of which is to guide the visually impaired in an outdoor environment. The human interface between the Robotic Travel Aid and the visually impaired is a very important component of it. In this paper, a human interface implemented by using a synthesis speech device and push button switches is proposed, which was designed based on the results of the user's requirement study. Experiments carried out by the visually impaired show the usefulness and effectiveness of the proposed human interface.