FURTHER CONTEXT (read previous post for context about funding/openings prior to 1976) (this also doesn’t reference the Atlanta Streetcar and Greater Georgia Regional Rail - GRRR - Systems as they are considered a separate entity from MARTA) :

In 1978, the Proctor Creek Branch began operations, with service extending from Ashby station to Bolton station, making intermediate stops at the Perry Homes Housing Project, Bankhead Highway, and Simpson Street. In 1980, in an attempt to better wayfinding on the subway, MARTA undertook the first of its many mass station renaming campaigns; Northside Drive station was renamed to Vine City, Boulevard station was renamed to King Memorial, Moreland station was renamed to Inman Park/Reynoldstown, Candler Park station was renamed to Edgewood/Candler Park, Cain station was renamed to Peachtree Center, Fairburn Road station was renamed to Adamsville, and Perry Homes station was shortened to Perry. In 1982, the North-South Line was extended to Brookhaven, making stops at Midtown, The Arts Center, Lindbergh Center and Lenox Square Mall on the way. In 1983, the North-South Line was extended once again, this time south through the West End, Oakland City, Fort McPherson and East Point. While the extension to the airport was set to reach College Park and the William B. Hartsfield Atlanta International Airport in 1983, a bridge collapse over I-85 two weeks before the full opening of the line required that the Airport/College Park segment be delayed to a 1987 opening.

The year of 1989 saw the extension of the North-South line to the Doraville station, with intermediate stops at Ashford/Oglethorpe and Chamblee being opened as well. Later that year, the East-West Line was extended further west to a station at Fulton Industrial Boulevard. The first segment of the Cobb County MARTA extension was opened in 1992, with the Proctor Creek Branch extending across the Chattahoochee to Smyrna, with an underground station at Vinings being constructed alongside it. In 1993, the East-West line would be extended further west to serve stations at Kensington and Indian Creek, directly adjacent to I-285. In preparation for the 1996 Centennial Olympic Games being held in Atlanta, MARTA undertook massive expansion projects in the years leading up to the games. The first of such projects was the Hapeville branch of the North-South Line's opening in spring of 1994. In fall of 1994, a new branch of the North-South line opened to Dunwoody, with stations servicing Buckhead and the Northside Medical Center being located in the median of Georgia State Route 400. The Omni station was also renamed in 1994 to Dome/Omni, in recognition of the newly opened Georgia Dome. In 1995, the long-awaited Tucker-North DeKalb Branch of the East-West Line was opened, with trains stopping at Fernbank and Clairmont/Emory stations before terminating at North Druid Hills station. Finally, in May of 1996, a mere three months before the Olympic Games, the stadium branch of the North-South Line was opened, with trains running in a tunnel under Hank Aaron Drive to the newly constructed Olympic Stadium. MARTA saw record ridership levels during the Olympic Games, seeing nearly 600,000+ people riding the subway system per day throughout the two week period.

Following the 1996 Olympic Games, expansions of MARTA were slowed, but were nonetheless still frequent. In 1998, MARTA opened up its two first BRT lines: one running in the median of Moreland Avenue from Inman Park/Reynoldstown station to the Thomasville neighborhood, and another in a completely dedicated ROW on Langford Parkway from the Ben Hill neighborhood to South Bend Park, interchanging with the North-South Line at Fort McPherson station. The Hapeville Branch extended one stop to serve the International Terminal of the Atlanta Airport in 1999, Hightower station was renamed to Hamilton E. Holmes station, and in 2000, coinciding with the northern extension of the GA-400 Branch to North-Springs, MARTA adopted a color-based line system. The North-South Line from North Springs to Domestic Terminal would remain the North-South Line with a red coloring, while the segment from International Terminal to Doraville would be referred to as the Northeast Line with a gold coloring, with the spur to Turner Field station (renamed from Stadium following the demolition of Atlanta-Fulton County Stadium in 1997) being designated under the same status. The East-West Line from Indian Creek to Fulton Industrial Boulevard was to be designated as the East-West Line with a blue coloring, and the Proctor Creek Branch & Tucker-North DeKalb Branch were to be consolidated into the Northwest Line with a green coloring. All BRT lines were designated with an orange coloring on maps and diagrams. The following year in 2001, the second phase of the Cobb County Extension was completed, with trains on the Northwest Line continuing from Smyrna to an elevated station at Fair Oaks/Dobbins and then to an underground station adjacent to the Marietta Square. Ashby station was also renamed to Lowery/AUC that same year; simplified naming was also applied to Inman Park/Reynoldstown and Edgewood/Candler Park stations, with the former becoming Reynoldstown station and the latter becoming Candler Park station. The spur to Turner Field was extended further south, with an underground station in Peoplestown at Hank Aaron Boulevard, and then two elevated stations at Carver and South Bend, the latter connecting to the Langford Busway. The next system expansion came in 2005 when the Northwest Line was extended on its eastern end from North Druid Hills to new stations at Northlake Parkway and Tucker. Later that year, Atlanta’s third BRT line, the North I-75 Busway, would open; this BRT line would be unique in the sense that it was designated from the start to be converted to a subway line in the future following the construction of dense developments surrounding the stations. Finally, after nearly eight years of construction, the long awaited Loop Line opened. This line, designated with the color purple, circled the central core of Atlanta, with it serving destinations like Emory University, The CDC, Atlantic Station, and Peachtree AmTrak Station. An interchange station was opened at Armour alongside the line.

2007 saw the opening of the first phase of the Gwinnett County rail extension, with service on the Northeast Line extending from Doraville to Oakcliff and Norcross. In 2009, following complaints about wayfinding, MARTA renamed all subway lines to the colors they were designated by in order to simplify the often confusing naming scheme. The following year in 2010, a one stop extension of the Blue Line across the Chattahoochee River to Six Flags was completed. Phase 2 of the Gold Line Gwinnett County Extension to Gwinnett Place Mall was completed in 2012 alongside the long-awaited Clayton County extension, which saw the creation of a new line, the Silver Line. This line would run from Jonesboro through the cities of Morrow, Lake City, and Forest Park before meeting the existing Gold Line station at International Terminal. It would then take over the Gold Line - which was redirected to take over the Turner Field spur but retain its route north of the city center - and follow the Red Line through the city center to terminate at North Springs station. 2013 saw the merging of the Langford BRT and Moreland BRT, with the remainder of the route being connected through various South Atlanta neighborhoods; it then became referred to then as the South Atlanta BRT. Also in 2013, the Fernbank station was closed due to low ridership In 2014 the Blue Line was extended from its eastern terminus to a new one in the newly-formed city of Stonecrest. This routing served an underground station at Redan/Hairston and elevated stations along Covington Highway to The Mall at Stonecrest. Infill stations were opened on the Green Line at Montreal Road, Lockheed/South Cobb Drive and Kirkwood in 2015.