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Tactile Walking Surface Indicators: Design Requirements & Installation Guide

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Tactile Walking Surface Indicators: Design Requirements & Installation Guide

Tactile Walking Surface Indicators (TWSIs), also referred to as detectable warning surfaces or tactile attention indicators, serve as standardized walking pathways that convey vital information to individuals with visual impairments through the use of distinctive textures and occasionally auditory cues.


These surfaces are typically constructed using inserts made of various materials such as metal, rubber, stone, or plastic, or they can be directly integrated into concrete ground surfaces. TWSIs are designed to offer a discernible texture underfoot, detectable by a long cane. Furthermore, their edges are intentionally angled or bevelled to minimize the risk of tripping.


Two main categories of TWSIs exist:


Attention TWSIs, also known as warning TWSIs, draw awareness to significant hazards such as the commencement of a staircase or the perimeter of a platform.


Guidance TWSIs, alternatively called wayfinding TWSIs, provide directional information within open spaces, aiding individuals in navigating along designated paths.


TWSIs should exhibit a noticeable contrast in color compared to the surrounding walking surface. For attention TWSIs, the recommended color is safety yellow (Munsell Colour System: hue 5.0, chroma yellow 8.0/12). Another effective approach involves using a light hue on a dark ground surface or a dark hue on a light ground surface. To clearly distinguish warning information from guidance information, it is advised not to employ safety yellow for guidance TWSIs.


When TWSIs are installed as pre-fabricated panels or affixed onto existing ground or floor surfaces, the panels themselves should feature bevelled edges. The base surface of the TWSI panels should not exceed three millimeters above the existing surface. While surface-mounted installations are less than ideal, they may be considered only when alternatives such as cast-in-place or recessed installations are not feasible.


TWSIs should always be attached firmly to prevent edges from lifting.


Attention Tactile Walking Surface Indicators


Attention Tactile Warning and Safety Indicators (TWSIs) play a crucial role in conveying vital safety information to individuals present in potentially hazardous areas, especially those with visual impairments. Their primary purpose is to serve as markers for identifying potential dangers. It is imperative to maintain uniform safety messaging to ensure that individuals with visual impairments can readily identify precarious situations regardless of their location, be it a town or province.


TWSIs should comprise circular or flat-topped truncated domes or cones that are securely installed on pedestrian surfaces.


Attention TWSIs should have the following specifications:


  • Flat-topped truncated domes or cones should be used, arranged in a square grid pattern, parallel or diagonal at 45 degrees to the main direction of travel.
  • The height of the flat-topped domes or cones should be four to five millimetres. In interior environments with exceptionally smooth surfaces, such as polished concrete or terrazzo, the minimum height of four millimetres is preferred.
  • The diameter of the top of the flat-topped domes or cones should be between 12 and 25 mm.
  • The diameter of the lower base of the flat-topped domes or cones should be 10 mm (+/- 1 mm) more than the diameter of the top.


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


Attention TWSIs should be used at the following locations:

  • Platform edges
  • Ferry dock edges
  • Edges of reflecting pools and fountains those are unprotected at ground level
  • Tops of stairs, at landings where there is a door leading onto the landing
  • At landings longer than 2,100 mm where there are no continuous handrails
  • Both sides of ground-level railway crossings
  • Curb ramps and depressed curbs
  • Unprotected edges with a drop-off greater than 250 mm in height
  • Unprotected edges where the slope down is greater than 1:3 (33 per cent)
  • Entry points to vehicular routes where no curb or other element separates pedestrians from vehicles
  • At the beginning of ground-level moving walkways (e.g., used in airport terminals)


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

  • 600 – 650 mm deep
  • Located at the edge of the drop-off
  • Running the full length of all unprotected platform/dock edges that border the drop-off


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 vision loss 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.


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.


Guidance Tactile Walking Surface Indicators


Guidance TWSIs should consist of a pattern of parallel, flat-topped, elongated bars that extend in the direction of travel.

Guidance TWSIs are appropriate at the following locations:

  • Transit stops
  • Train stations
  • Subway or light rail transit (LRT) platforms
  • Airports
  • Sports arenas and stadiums
  • Large open spaces (e.g., public squares)
  • In the door areas of expansive open areas (e.g., shopping malls)


Follow these specifications for guidance TWSIs:

  • Where installed to define a route, their width should be 250 – 300 mm.
  • Where installed across a route as an indicator of an amenity or diverging route, their width should be 600 – 650 mm.
  • They should have a minimum continuous clearance of 600 mm on both sides.
  • The height of the bars should be four to five millimetres.
  • The top of the flat-topped elongated bars should have a width between 17 and 30 mm.
  • The bars should be colour contrasted to surrounding surfaces to make them easily identifiable by people with low vision.
  • The width of the base of the bars should be 10 mm (+/- 1 mm) wider than the top.
  • The top length of the bars should be at least 270 mm. If drainage is a concern, a space of 10 – 30 mm should be provided at the ends of the bars.
  • The spacing between adjacent flat-topped bars should be adjusted depending on the size of the bars. The larger the individual bars, the more distant the space between them.
  • Attention TWSIs should be used along tactile guidance paths to identify turns and other decision-making points. The attention TWSIs should be configured in a square pattern centred on the guidance TWSIs, with each side of the square being 600 mm – 650mm.


An alternate type of guidance TWSI should be used on road surfaces to assist persons with vision loss to navigate complex road crossings including, but not limited to crossing at:

  • Roundabouts, also known as traffic circles
  • Mid-block crossings with four or more lanes
  • Skewed intersections
  • Offset crossings


TWSIs used on road surfaces are clearly different and distinguishable from the guidance surfaces used in pedestrian areas. Guidance TWSIs on road surfaces at pedestrian crossings should:

  • Be configured as a straight path
  • Be 250mm - 300mm wide
  • Be detectable underfoot
  • Be detectable with a long cane
  • Be at least 50% colour/brightness contrasted with adjacent road surfaces
  • Not present a tripping hazard
  • Not present a barrier for persons who use wheelchairs or other types of mobility devices
  • Be configured to mitigate damage from snow-plowing