The critical flow ratios for a three-phase signal are found to be 0.30, 0.25 and 0.25. The total time lost in the cycle is 10s. Pedestrian crossing at this junction are not significant. The respective Green times (expressed in seconds and rounded off to the nearest integer) for the three phases are

50, 25 and 25

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40,25 and 25

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40, 30 and 30

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34,28 and 28

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Solution

The correct option is D 34,28 and 28
Cycle length
$C = \frac{1.5 L + 5}{1 - y}, L = 10 s e c$
$y = y_{A} + y_{B} + y_{C}$
$= 0.3 + 0.25 + 0.25$
$= 0.8$
$C = \frac{1.5 \times 10 + 5}{1 - 0.8} = 100 s e c$
Effective Green times
$G_{A} = \frac{(C - L) y_{A}}{y = y_{A} + y_{B} + y_{C}} = \frac{(100 - 10) \times 0.3}{0.8}$
$= 33.75 \approx 34 s e c$
$G_{B} = \frac{(C - L) y_{B}}{y = y_{A} + y_{B} + y_{C}} = \frac{(100 - 10) \times 0.25}{0.8}$
$= 28.125 \approx 28 s e c$
$G_{C} = \frac{(C - L) y_{B}}{y = y_{A} + y_{B} + y_{C}} = \frac{(100 - 10) \times 0.25}{0.8}$
$= 28.125 \approx 28 s e c$
option (a) [34,28,28]

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