Andy in Oshawa Ontario has a basement stairway that is too steep, it is difficult to walk down this stairway. He says that he can't change the stairway and only wants to cover the treads with something that will give him a bit of a grip.
Because of our snow, in most of Canada you can buy rubber stair treads for winter use. These could be nailed to the treads of Andy's stairs as they are specifically made to increase grip. If he can't find that, then I would suggest the anti-skid adhesive strips that are sold for the bottom of bathtubs. You might want to glue and nail them down to make sure they don't come loose.