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Attention Tactile Walking Surface Indicators

Attention TWSIs provide critical safety information to everyone at potentially dangerous locations, and particularly to people impacted by blindness. They should only be used to identify potential hazards.

A drawing of attention TWSIs showing dimensions (described in text).

It’s important to provide consistent safety information so that people impacted by blindness will recognize potentially dangerous situations in any town or province.

Attention TWSIs should consist of circular, flat-topped, truncated domes or cones installed on a walking surface.

Attention TWSIs should have the following specifications:

The spacing between adjacent flat-topped domes or cones should be adjusted depending on their size, as shown in the table below. The larger the individual domes/cones, the more distant the space between them:

A table showing the spacing between domes/cones, based on their top diameter.
Top diameter of flat-topped domes or cones (mm) Spacing between the centres of adjacent domes or cones (mm)
12 42 to 61
15 45 to 63
18 48 to 65
20 50 to 68
25 55 to 70

A top diameter of 12 mm is the optimal size of domes or cones for people impacted by blindness to detect and distinguish through the soles of their footwear.

Attention TWSIs should be used at the following locations:

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Attention TWSIs used on curb ramps at an intersection. The TWSIs are bright yellow, in contrast to the adjacent concrete and asphalt ground finishes.

Attention TWSIs used on platforms, ferry docks and other drop-offs should be:

For more information, refer to our sections on Platform Edges and Transit Facilities.

At stairs, attention TWSIs should commence one tread depth back from the leading edge of the nosing at the top step and extend across the width of the stairs. The attention TWSI alerts a person with blindness that there is a set of stairs ahead and to seek the support of a handrail for safe navigation. The depth of the TWSIs used at the top of stairs should be 600 – 650 mm. For more information, refer to our section on stairs.

At railway crossings, attention TWSIs should be located so that the edges of TWSIs are 1,800 – 4,600 mm from the centre line of the nearest rail. Attention TWSIs should be installed in addition to any mechanical barriers that are activated with the arrival of trains.

Attention TWSIs should be provided across the entire width of a curb ramp or depressed curb (exclusive of flares). They should be set back 150 – 200 mm from the curb’s edge and extend 600 – 650 mm in the direction of travel. For more information, refer to the section Curb Ramps and Depressed Curbs. Guidelines on TWSIs can be found in the section Escalators and Moving Walkways.