Since the BMT was not amenable to the neat IND system, the TA had to make some compromises. They tried to follow the IND system of single-letter expresses and double-letter locals, but the system began to break down under the complex BMT routings. Where on the IND a local simply doubled the express letter (A Eighth Avenue Express, AA Eighth Avenue Local), some lines had multiple local services with different routings. For instance the two Brighton Local services, one via the Manhattan Bridge and the other via the Montague Street Tunnel, were designated QB and QT respectively. The TA had no specific lettering plan for the two Wall Street special rush-hour services, so it just designated these M (Nassau Street Express) temporarily, a letter reserved for use on the BMT Myrtle Avenue Line's Nassau Street service.