Traffic Lights are items in All Star Smashers. Tapping the A button next to them switches it onto red, pausing anything next to it for a while. If an item appears right next to them, they will not be able to be used until the lights turn green.
When the lights turn amber, it warns everyone that everything will resume shortly.
When the lights turn green, everything resumes and items next to it can also be picked up. Any moving objects or opponents that were stopped next to the lights will get a boost after resuming to green.