Which of the following is NOT a common mode of operation for timing plans in a signal system?

In traffic signal control, timing plans are essential for managing traffic flow and optimizing signal performance. A fixed schedule is indeed a mode of operation, but it is typically not as flexible or responsive to live traffic conditions compared to the other modes.

The time of day operation allows signal timing to adjust based on the changes in traffic patterns throughout the day, such as morning and evening rush hours. Traffic responsive systems adapt to current traffic conditions by changing their timing plans based on real-time data, allowing for optimal flow during varying traffic levels. Traffic adaptive systems take this a step further by continuously monitoring conditions and making adjustments without a pre-determined schedule, providing a highly dynamic response to traffic demands.

In contrast, a fixed schedule does not change based on real-time conditions; instead, it uses predetermined timings regardless of the actual traffic situation. This rigidity can lead to inefficient traffic management during unexpected fluctuations in traffic volume, making it less effective compared to the flexible, responsive nature of the other operational modes.

Thus, the correct understanding is that a fixed schedule does not align with the common operational strategies that prioritize adaptability and real-time responsiveness in modern signal systems.