The BMT Broadway Line is a rapid transit line of the BMT division of the New York City Subway system. The line was built as a part of the BRT Broadway–Fourth Avenue Subway. Trains of the N and Q serve the express run via the Manhattan Bridge and the R line serves the local (the R extends into Brooklyn via the Montague Street Tunnel). The line is often referred to as the "N 'n' R" due to the N and R services that were the only services which continued to operate over the line during the long years of closure of the Manhattan Bridge south tracks. Trains using this mainline are assigned the color yellow.