The lost time due to starting delay on a traffic signal approach is noted as 2 seconds, the actual green time is 24 seconds and the amber time is 4 seconds. How much is the effective green time?
- A19 sec
- B22 sec
- C25 secCorrect
- D28 sec
Solution
Concept
Effective Green Time
Formula
Effective Green Time = Actual Green Time + Amber Time - Total Lost Time
Step-by-step solution
1. Identify given values: Actual Green Time = 24 s, Amber Time = 4 s, and Total Lost Time = 3 s (2 s start-up delay + 1 s clearance loss). 2. Substitute values into the formula: Effective Green Time = 24 + 4 - 3. 3. Calculate the result: 25 seconds (Option C).
Explanation
Effective green time is calculated as actual green time plus amber time minus total lost time. Taking standard clearance lost time as 1 second along with the 2-second start-up delay gives a total lost time of 3 seconds, so 24 plus 4 minus 3 equals 25 seconds.
Shortcut
Effective Green = (Green + Amber) - Lost Time. Add green and amber together, then subtract startup and clearance delays.
Common mistake
A common mistake is failing to include the amber time and subtracting the start-up delay directly from the actual green time (24 - 2 = 22 seconds, Option B), or adding the green and amber times together while ignoring the lost time completely (24 + 4 = 28 seconds, Option D).
Correct answer: C) 25 sec