Blister Profile
The purpose of this surface is to warn visually impaired people of the edge of all off-street railway platforms.

Definition
The profile of the platform edge (off-street) warning surface consists of off-set rows of flat-topped domes 5mm (+/-0.5mm) high, spaced 66.5mm apart from the centre of one dome to the centre of the next. The surface pattern is different to the blister surface used to warn of the absence of a kerb upstand at pedestrian crossing points.

Application The platform edge warning is recommended for use at all off-street rail platforms including: • Heavy rail platforms • Off-street light rapid transit (LRT) • Underground platforms Layout The platform edge (off-street) warning surface should be laid immediately behind the platform edge coping stone. In most cases this will be between 600mm and 700mm back from the platform edge, but in some circumstances this may be as little as 500mm. It should never be less than that because people may not have enough time to stop walking once they have detected the tactile surface.