on the line in the 1957 and used until 1997, when a route selector punch box with B1 Astoria, local/express buttons was installed at the 10/11 car marker on the upper level of Queensboro Plaza. IDENTRA used a removable round circular disc type radio antenna assembly, slide-mounted on the small mounting brackets that were attached on the front of R12, R14, R15, and R17 cars that were assigned to the 7 route, which had been used on the line since 1948. Similar to the use of radio transponders in the CBTC installation, the system used the antennas to determine whether a train was running local or express, and then accordingly switched the track at interlockings near the Queensboro Plaza and Flushing–Main Street stations. This move reduced the number of signal towers on the line from 9 to 2 and theoretically allowed to operate 37 eleven-car trains instead of only 30 nine-car trains per hour. The consolidated signal system was in use by 1956 while the selector system was in service by 1958. However, in practice, train frequencies were not necessarily increased. According to an experiment performed by the Long Island Star Journal in 1957, rush-hour headways ranged from 6 to 15 minutes between local trains, and 2 to 6 minutes between express trains. In 1953, with increased ridership on the line, a "super-express" service was instituted on the line. The next year, the trains were lengthened to nine cars each. Subsequently, the trains were extended to ten cars on November 1, 1962. With the 1964–1965 World's Fair in Flushing Meadows–Corona Park in April 1964, trains were lengthened to eleven cars. The Flushing Line received 430 new R33S and R36 cars for this enhanced service. Rolling stock along the Flushing Line received "strip maps" in 1965, the first such installation in the system. The strip maps showed only the stations on the Flushing Line, as opposed to for the entire system, but the transfers available at each station were listed. Decline and rehabilitation As with much of the rest of the subway system, the IRT Flushing Line was allowed to deteriorate throughout the 1970s to the late 1980s. Structural defects that required immediate attention at the time were labeled as "Code Red" defects or "Red Tag" areas, and were numerous on the Flushing Line. Some columns that supported elevated structures on the Flushing Line were so shaky that trains did not