For much of the 20th century, the Howard–Englewood/Jackson Park route was equally compatible in terms of passenger service until the late 1960s through the 1970s. However, passenger traffic volumes began to shift on the south side lines, with more riders using the newer Dan Ryan line (which runs four miles (6 km) further south) and fewer riders on the older "L" lines. This level of ridership allowed the CTA to develop a more efficient system by combining the more heavily used rail lines together and combining the other lines together, providing increased service capacity for the routes that need it. The Red Line was created in 1993, when the CTA adopted color-coded system for all of its "L" routes. On February 21, 1993, a new connection opened from the State Street subway south of Roosevelt to Cermak–Chinatown. The Howard branch was paired with the Dan Ryan branch creating the current Red Line and the Lake Street branch was paired with the Englewood and Jackson Park branches to form the Green Line. A further operational benefit of this switch was that this freed up capacity in the Loop needed for the addition of the Orange Line to Midway Airport. The former tracks used to move West-South trains from the Loop to the Dan Ryan line are still retained for non-revenue moves and service disruptions.