 One of the Belgium-specific blocks uses metal disks of roughly 85mm in diameter and 8mm in height.In Japan, the prescribed size of warning block protrusions is 22mm in diameter (±1.5mm) and 5mm in height, a size designed to promote mobility by the vision impaired without impeding the movement of wheelchair users or elderly pedestrians.Given the large size, height and slipperiness of the metal disks used in the Belgian blocks, they are likely to present a significant obstacle for wheelchair users, children and the elderly.