Tactile Paving Calculator - Blister & Corduroy Surface Quantities

Red blister tactile paving is mandatory at controlled (signalised) crossings — pelican, puffin, toucan and signalised zebra crossings. The red colour itself tells partially sighted people that the crossing is controlled, so red must never be used at an uncontrolled crossing. At uncontrolled crossings use buff, or any colour other than red that contrasts with the surrounding footway. Off-street rail and tram platform edges use a separate offset-dome warning surface that can be any colour except red. This is the reverse of a common misconception, so getting it right matters: laying buff at a signalised crossing removes the controlled/uncontrolled distinction that visually impaired pedestrians depend on. (DfT, Guidance on the Use of Tactile Paving Surfaces, 2021: controlled-crossing colour Chapter 1 section 1.5.1; uncontrolled-crossing colour section 1.5.2; off-street platform-edge surface Chapter 3 section 3.2.)

Blister surfaces have flat-topped domes (blisters) arranged in a regular grid pattern and are used at pedestrian crossings to indicate the transition from footway to carriageway. Corduroy surfaces have parallel raised ribs (like corduroy fabric) and are used as hazard warnings at the top and bottom of steps, at level crossings, and where a footpath meets a shared cycle route. Each surface type conveys a different message to visually impaired pedestrians.

At a controlled crossing (pelican, puffin, toucan) the red blister surface should extend 800mm back from the kerb face, increasing to 1200mm where the dropped kerb is in the direct line of travel — for example at a junction. At an uncontrolled crossing only 400mm depth is needed where the crossing is inset (the dropped kerb is not in the direct line of travel, as at a typical side road, so it is met at an acute angle); where the flush dropped kerb is in the direct line of travel for people walking the surface should be 1200mm deep across the full width of the dropped kerb. For an off-street platform edge the offset-dome warning strip is 400mm deep, set back from the platform edge — usually 600mm to 700mm, and never less than 500mm. Corduroy hazard warning at steps is 800mm deep where in the direct line of travel, starting 400mm from the top or bottom step nosing. (DfT 2021 guidance: controlled-crossing depth Chapter 1 section 1.5.1; uncontrolled-crossing depth section 1.5.2; corduroy steps Chapter 2 section 2.5.2; off-street platform edge Chapter 3 section 3.5.)

The crossing blister surface has flat-topped blisters 5mm high (±0.5mm) and about 25mm in diameter, arranged in straight rows (a square grid) on a standard 400mm × 400mm slab. Note the 66.5mm centre-to-centre spacing often quoted online is the OFFSET-dome layout of the separate off-street platform-edge warning surface, not the pedestrian-crossing blister — the Department for Transport guidance explicitly states the platform-edge surface "is different to the blister surface used at" crossings. These profiles are specified in the DfT "Guidance on the Use of Tactile Paving Surfaces" (2021), Chapter 1 section 1.2 (crossing blister) and Chapter 3 section 3.2 (off-street platform edge), and ensure the surface is detectable underfoot and by a long cane.