An important part of ensuring the safety of stairs is making sure the steps are clearly visible. This is especially true for commercial properties, but can also be crucial for private homes — particularly if the occupants are visually impaired to some extent.
You should conform to, or exceed, your local building code, but if there isn’t a section on this subject you could follow the California code. It states,
“Interior stairs shall have the upper approach and lower tread marked by a stripe providing clear visual contrast. Exterior stairs shall have the upper approach and all treads marked by a stripe providing clear visual contrast.
“The stripe shall be a minimum of 2 inches wide to a maximum of 4 inches wide placed parallel to, and not more than 1 inch from the nose of the step or upper approach. The stripe shall extend the full width of the step or upper approach and shall be of material that is at least as slip resistant as the other treads of the stair. A painted stripe shall be acceptable. Grooves shall not be used to satisfy this requirement.”
Safety Direct America offers both anti-slip floor paints and adhesive-backed anti-slip tapes that are verified slip-resistant when wet. Don’t use ordinary paints! Adding sand (silica) to ordinary paint is not a good idea — its points are brittle and will break soon under traffic; and it’s a skilled art to select the right size and area density of the abrasive and then hold it in place without risk of the paint masking its slip-resisting quality, temporary though that may be.
Another good idea, though not required by most Codes, is to remind people to use the handrail. The photo below shows a typical sign. This is like free insurance!