People with blindness or visual impairment live and use cities, but they could enjoy them and take advantage of ADA truncated domes more if they had the ability to move autonomously and safely. For this, they must be able to orient themselves and avoid obstacles and risks of all kinds. 
The unevenness between the road and the sidewalk has acted, on the other hand, as a longitudinal guide, and as a protective order to avoid the danger of invading, unconsciously, the vehicular circulation space. This gap has been progressively eliminated in pedestrian crossings in cities, in order to improve general mobility and remove barriers for people with motor disabilities, especially wheelchair users. This also eliminates the possibility for people with visual impairment to detect the limit of the safe area to travel.
Unevenness
To avoid this, since the 1960s, some countries began to install podotactile pavements and ADA truncated domes, which by means of low or high-relief forms were used to transmit orientation and safety information to these people. These pavements became generalized from the 1980s in European countries and in the United States, beginning by signaling the edges of railway platforms and other limits with unevenness.
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The transmission of this information also raises technical problems: people with visual disabilities manifest very different abilities to interpret their environment to navigate and navigate safely through the city. Not only the characteristics of its limitation, but other aspects such as its educational level, acquired abilities, the age of the disability or the type of training received will determine the possibilities of interpretation of signals and stimuli that allow its autonomous circulation in the city.
For this reason, it has become necessary to reduce the elements of this language to the minimum expression by using two main types of podotactile pavements, which are easy to identify, and which form the basis of a simple sign language. One is formed by a surface of buttons (ADA truncated domes, truncated pyramids or cylinders) and the other by a surface of bands along its entire width. Both can help blind people to follow a particular path using their feet and stick to detect and distinguish their raised patterns on the pavement.
It is affirmed that ADA truncated domes and mats have emerged as a way to compensate for the total or partial loss of vision through the provision of complementary haptic information. In the most developed cities of the world, signs have been implemented on the pavement that allows people with visual disabilities to be warned about the proximity of a danger point, such as a road junction or railroad tracks. Although there are many technological aids already available or in development to facilitate their location, mobility, and orientation in the city, the use of ADA truncated domes and tactile pavements is still a basic element to make the city accessible to people with visual disabilities.
