Saturday, February 23, 2008

Tactile Ground Surface Indicators

Tactile Ground Surface IndicatorsABC Radio National By Design program had a segment on Tactile Ground Surface Indicators (TGSI) today. The guest was Murray Mountain, Chairman, Australian Standards Technical Committee ME/64. TGSIs are bumps or ridges on the ground to help people with limited eyesight to find they way around. Australia leads the world in standards and design of TGSIs and you will see them at Australian railway stations on the edges of platforms, and at the bottom and tops of flights of stairs in public buildings.

As Murray described them, the most common indicators are truncated cones 4 to 5 mm high. They are arranged in a rectangular grid. The indicators are designed not only to be easily felt through the feet or with a cane, but also to be seen. Their design has been carefully researched to make them prominent enough to be noticeable, but not a tripping hazard. Also they have to be long lasting and easy to install.

The Australian Human Rights and Equal Opportunity Commission (HREOC) released Guidelines on access to buildings and services in 2007. This provides guidance to designers, builders, planners, certifiers, building managers and access consultants about access to buildings and services for people with disabilities, inlcuding use of TGSIs. This accompanied by The good, the bad and the ugly – design and construction for access which has examples of what can go wrong. The first problem covered is inappropriate use of TGSIs.

As well as the round knobs for warning of a hazard, there are directional tiles with ridges to steer people in a particular direction, such as to the entrance to a railway station. Usually the directional tiles end with the warning tiles, to indicate where to stop. I saw an unfortunate absence of warning tiles on the footpath outside the Beijing Committee for the 2008 Olympic Games headquarters. Directional tiles had been laid down the center of the footpath with no warning tiles. So the path guided people into obstructions such as poles and off the high curb into six lanes of traffic. In contrast the Sydney Olympics had a clear policy for use of the paths and was praised for its efforts.

As Australia is the leader in TGSI standards, there would be an opportunity for training materials, planning an installation aids. These could be web based and include tests and checks. The would appear to be a large market for such support in China.

Standards and guides include:
  1. AS/NZS 1428.4:2002 Design for access and mobility - Tactile indicators
  2. TRAINING PROGRAM Tactile Ground Surface Indicators Workshop - 1428.4
  3. BS 7997:2003 Products for tactile paving surface indicators. Specification
  4. DR 04020 Design for access and mobility - Part 4.1: Tactile indicators
  5. JIS T 9251:2001 Dimensions and patterns of raised of parts of tactile ground surface indicators for blind persons
TGSIs are also known as tactile guide pathways and Tactile paving. US ones are known as Detectable Warnings and use truncated domes, rather than cones. The indicators need not be any particular color, but must have sufficient contrast to be easily seen. The international work is under Working Group ISO/TC 173/WG 7 - Provisions and Means for Orientation of Visually Impaired Persons in Pedestrian Areas.

In Japan, TGSIs are commonly known as
"Braille Blocks" (Tenji Block) , by analogy to Japanese braille (Tenji 点字). The paths (usually yellow) do not use braille, just the same grid of dots as used in Australia.

See also books:
  1. Americans with Disabilities Act


michaeltvs said...

Brilliant, thanks for the links in this article. Our council (Townsville) re-vamped some inner city streetscapes and created what is no less than a disaster area. It took out a wooden spoon prize from Dept of Heritage on how not to re-design a hertit6age precint. There have been numerous injuries sustained by people in the area too, they laid TGSI's in most places in reverse (ie: strips for dots) and also erected bollards and sculptures with sharp edges at below waist height. Another problem is that the TGSI's lift off in the heat, as most people wear minimal footware you see quite a few bloodied toes. I might go down take a few shots and send them into HREOC and DEH, council are well aware of what is going on

lay said...

I'd like to know how these TGSI's are used by the visually impaired traveller. What do they do with the dots?