Which of the following is/are NOT the characteristic of traffic actuated signals? i. It is costly. ii. The cycle time changes as per traffic demand. iii. The cycle time changes as per the time of the day. iv. Computers and detectors are used to operate this signal.
- ABoth ii and iv
- BOnly ii
- COnly iiiCorrect
- DBoth iii and iv
Solution
Concept
Traffic actuated signals change timing according to the actual traffic detected, not according to the time of day.
Step-by-step solution
1. Traffic actuated signals use detectors and a controller (computer) to sense vehicles, so statement iv is true. 2. Their green time and cycle time change with traffic demand, so statement ii is true. 3. Detectors and controllers make them costly, so statement i is true. 4. Changing the cycle time as per the time of the day is a feature of fixed-time (multi-programme) signals, not actuated signals, so statement iii is NOT a characteristic. 5. Answer: Only iii.
Explanation
Traffic actuated signals sense vehicles with detectors and adjust timing to actual demand. They are costly because of the detectors and controllers. A change of cycle time by time of day (peak and off-peak plans) belongs to pre-timed or fixed-time signals.
Why the other options are wrong
A: ii and iv are true characteristics of actuated signals. B: ii is a true characteristic. D: iv is a true characteristic, so iii alone is the correct choice.
Shortcut
Actuated = demand based; time-of-day based = fixed-time signal.
Common mistake
Confusing time-of-day plans of fixed-time signals with demand-based actuated control.
Correct answer: C) Only iii