Which type of signal operation is activated by detected vehicles on a side road?

• A. Pretimed operation
• B. Semi-actuated operation
• C. Full actuated operation
• D. Static operation

Answer: (B)

Semi-actuated operation is the correct answer because it specifically refers to a traffic signal system that is triggered by vehicles detected on a less busy side road, while the main traffic flow operates on a fixed cycle. In this type of operation, the signal for the side road changes in response to the presence of vehicles, allowing for efficient traffic management without the need for continuous activation.

In semi-actuated signals, the main road generally has a pre-timed cycle for its green light, while the side road's green light is activated only when vehicles are detected waiting at the stop line. This leads to improved traffic flow and reduced waiting times for side road traffic, making it an effective solution in scenarios where side road traffic is less frequent.

In contrast, a fully actuated operation involves all movements being monitored and affected by vehicle detection systems; it dynamically adjusts the signal timing based on real-time traffic conditions on all approaches. This method is typically used in busier intersections where all lanes require adaptive timing.

Pretimed operation describes a system where signal timings are fixed and do not change in response to actual traffic conditions, which can cause inefficiencies at intersections with variable traffic volumes. Static operation refers to a situation where signals do not change at all, and thus, do