Some of Singles & Sociables outings do not need a Hike Code nor even a Trans Code. The subject lines will usually contain the word "Singles" or "Sociables"; and (S) to indicate the sponsoring committee.
When outings need to be classified by difficulty or skill requirements, or can hook up with public transportation that corresponds to the index already set up the Committee uses basically the same classification system as other Activity Committees. These codes being the:
1) Hike Code
2) Trans Code