Page 129 - Lecture Notes DCC3113

3. Two phase traffic light is suggested for a junction. Based on Table, determine
i. Total of loss time, L
ii. Optimum Cycle Length, Co
iii. Effective green time for each phase
iv. Actual green time for each phase
v. Sketch the time phase diagram

Table
Direction/Cabang North/Utara South/Selatan East/Timur West/Barat
Actual flow/Aliran Sebenar (q) 550 700 500 880
pcu/h
Saturation Flow/Aliran Tepu,
S (pcu/hr) 1975 1975 1875 1875

Given: Intergreen time = 5 seconds
Amber period = 3 seconds
Lost time = 2 seconds
(15 marks)

Answer :
i. Total Lost Time, L

L = ∑ℓ + ∑( I – a)
= [2 + 2] + [ (5 - 3) + (5 – 3)]

= 8 sec. ≤ 0.85 (OK)

ii. Optimum cycle, Co
Determine Y and ∑Y

Direction/Cabang North/Utara South/Selatan East/Timur West/Barat
Actual flow/Aliran Sebenar (q) 550 700 500 880
pcu/h
Saturation Flow/Aliran Tepu, 1975 1975 1875 1875
S (pcu/hr)
y = q/S 0.28 0.35 0.27 0.47
y max 0.35 0.47

Y = ∑Y max
= (0.35 + 0.47) = 0.82

Determine the optimum cycle time, Co

Co = 1.5 L + 5
1 - Y

= 1.5 (8) + 5
1 - 0.82

= 94 sec
iii. Effective Green Time for Phase 1 and 2, g

g = Co - L = 94 - 8 = 86 sec

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