The article discusses different types of recalls in traffic signal controllers and how they operate. Recalls are modes that make specific traffic lights turn green even if no cars or pedestrians are detected. The study explains four common recall types: Vehicle, Pedestrian, Maximum, and Soft Recalls. The researchers also talk about the benefits of using a delayed recall system that can wait before activating a green light if there is little traffic. This delay helps optimize traffic flow and can be useful in certain situations. Overall, the article looks at how these recall modes function and explores the advantages of having controllers that can delay activating green lights based on traffic conditions.