In this paper the alternative method for determination of all possible lower reachability indices has been proposed. Method is based on the extension of parallel digraphs creation algorithm presented previously. As a solution of problem of determination of lower reachability index, method finds all possible finite paths in the digraphs - each of them representing one of the indices. By performing complete traversal of the digraphs we are able to reach all the possible lower reachability indices for any number of variables at once. Proposed method is illustrated by a numerical example.