Peak Hour Factor from 15-Minute Counts
Easytraffic flowpeak hour factor
Fifteen-minute traffic counts during the peak hour on an arterial are 420, 510, 540 and 480 vehicles. The peak hour factor is most nearly:
- A0.78
- B0.90
- C0.96
- D1.00
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Answer: B. 0.90
The peak hour volume is 420 + 510 + 540 + 480 = 1,950 veh/h, and the highest 15-minute count is 540 veh. The peak hour factor is PHF = V/(4 × V₁₅) = 1,950/(4 × 540) = 1,950/2,160 ≈ 0.90. A PHF of 1.00 would mean perfectly uniform flow across all four quarter-hours, which real traffic rarely achieves.
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