In 1979 3M revamped its technology--sold under the Opticom brand--to allow it to recognize two different priority levels: a high level for emergency vehicles, which could force traffic lights to change immediately and a lower level for transit vehicles, which could hold off changing the light entirely if changing the light to green would snarl traffic.
This ensures important applications that require high-speed connectivity, such as online games and video chat, get priority over less important traffic, such as incoming email or system updates.