In a signal design as per the Indian Road Congress specifications, the sum of the ratios of normal flows to saturation flows of two directional traffic flows is 0.50. The optimum cycle length as per Webster method is 30 sec. Estimate the total lost time per cycle.
- A5.67 sec
- B6.67 secCorrect
- C7.67 sec
- D8.67 sec
Solution
Concept
Optimum cycle
Formula
C₀ = (1.5L + 5)/(1 − Y)
Step-by-step solution
1. 30 = (1.5L + 5)/(1 − 0.5) ⇒ 15 = 1.5L + 5. 2. L = 6.67 s.
Explanation
Solve the Webster formula for the lost time.
Why the other options are wrong
Other values do not satisfy it.
Shortcut
L = (0.5C₀(1−Y) − ...)/1.5.
Correct answer: B) 6.67 sec