Tactile warning blocks are becoming so popular nowadays that they vary widely in material, shape and disposition of convex parts. Their placing conditions are also inconsistent in many locations. Consequently the circumstances are causing more and more perceptional confusion of visually disabled persons. In this paper, we studied tactile perceptability of floor samples including several types of tactile warning blocks under various placing conditions, for the purpose of standardization of tactile warning blocks and thier placing rules.