Clumping is a phenomenon in the 3D Universe and HD Universe games of the Grand Theft Auto franchise. This phenomenon is displayed by both pedestrians and vehicles, and its presence and 'severity' vary from game to game.
Pedestrian Clumping
Pedestrian Clumping is a form of clumping, in which many pedestrians with the same model spawn in the same area. This form of the phenomenon is much more common in the 3D Universe games, due to the limited number of pedestrian models available to use in-game. Pedestrians with the same model will act as they would normally, but it can be jarring to see two pedestrians who look identical to each other engaging in conversation, fighting, or carrying out other actions. Due to the vast amount of Pedestrian models in the HD Universe games, and the presence of two or more models for each class of pedestrian, this form of clumping happens far less in those games.