Transportation Engineering

Peak Hour Factor

The hourly volume divided by four times the busiest 15-minute volume within that hour.

Traffic within the peak hour is not uniform, and capacity analysis is done for the busiest 15 minutes. The peak hour factor PHF = V/(4·V₁₅) captures how peaked the hour is: 1.0 means perfectly even flow, and urban values commonly lie between about 0.85 and 0.95.

The design flow rate is the hourly volume divided by the PHF, which is always at least as large as the hourly volume. Multiplying instead of dividing produces a flow smaller than what was counted, and is the standard distractor.

How much of the FE Civil exam is Transportation Engineering?