The Rapid Transit Series (RTS) city bus is a long-running series of transit buses that was originally manufactured by GMC Truck and Coach Division during 1977, in Pontiac, Michigan. First produced in 1977, the RTS was GMC's offering of an design (the other entry was the Grumman 870 by competitor Flxible) and is the descendant of GMC's prototype for the U.S. Department of Transportation's Transbus project. The RTS is notable for its then-futuristic styling featuring automobile-like curved body and window panels; the Advanced Design Buses were meant to be an interim solution between the high-floor transit buses that preceded them, such as the GMC New Look (which had a curved windshield, but flat side glass and body panels), and modern low-floor buses that would facilitate passenger boarding