How far apart should tactile strips be installed from each other?

To recreate the common 400mm sq corduroy tile pattern with tactile strips:

Each corduroy tile has 8 rows of ribs to complete the 400mm sq area.

The ribs are 20mm in diameter and 400mm long.

The distance between each rib vertically is 50mm from the central point of the rib to the central point of the next rib.

For larger diameter strips, the distance between each strip should be 30mm between the edge of each strip.

For a detailed drawing of the corduroy tile layout – Click Here