Sentence:  Perhaps no aspect of library design is as vital to the success of library users as is effective <WSD>signage</WSD>, and certainly few other aspects are as perplexing for library planners. [...] Librarians often cannot rely on architects and interior designers to plan effective <WSD>signage</WSD> and must address this feature of library building design on their own. 
Meaning of the word marked with <WSD> tags:  Signs, particularly those imparting commercial, directional, or road traffic information, taken collectively.