The Clue Traffic signal?
The Answer SIREN
The answer "siren" fits the clue "traffic signal" because sirens are often used by emergency vehicles like police cars and ambulances. When these vehicles are responding to an emergency, their sirens alert other drivers to clear the way. In this way, a siren acts as a signal in traffic, helping to manage the flow and ensure safety. So, it makes sense to think of a siren as a type of traffic signal.