What type of traffic control signal functions without actuation?

The correct answer is pre-timed traffic control signals, which are designed to operate on a fixed schedule without needing any form of actuation based on vehicle presence or pedestrian demand. These signals change at predetermined intervals regardless of the traffic conditions at the intersection.

Pre-timed signals are often used in areas with consistent traffic patterns, where the volume of vehicles does not vary significantly throughout the day. This allows for predictable traffic flow and simplifies the implementation since the timings can be set up ahead of time and do not require real-time adjustments.

In contrast, actuated signals rely on vehicle or pedestrian presence to change their phases, adapting in real time to the conditions at an intersection. Dynamic and adaptive signals also involve varying timings based on traffic flow, but they include sensors and algorithms to modify their operations based on observation of current conditions. The primary distinction of pre-timed signals is their consistent operational pattern that does not adapt to real-time traffic inputs.