Civil Engineering PE Transportation and Traffic Engineering 3 — Questions and Answers
Question 1: A two-lane highway has a directional split of 60/40 and a PHF of 0.90. The directional design hourly volume (DDHV) based on an AADT of 12,000 vpd and a K-factor of 0.10 is:
- 720 vph (Correct answer)
- 648 vph
- 800 vph
- 540 vph
Correct answer: 720 vph
DDHV = AADT × K × D = 12,000 × 0.10 × 0.60 = 720 vph.
Question 2: For a level terrain two-lane highway, HCM defines LOS E as the level where percent time-spent-following (PTSF) exceeds:
- 80% (Correct answer)
- 65%
- 75%
- 90%
Correct answer: 80%
HCM defines LOS E on two-lane highways as PTSF > 80%, indicating heavily congested following conditions.
Question 3: A driver traveling at 55 mph requires an emergency stop. Assuming a deceleration rate of 11.2 ft/s² and 0 perception-reaction time, the braking distance is approximately:
- 264 ft (Correct answer)
- 330 ft
- 198 ft
- 440 ft
Correct answer: 264 ft
Braking distance = V²/(2a) = (55×1.467)²/(2×11.2) = (80.7)²/22.4 = 6512/22.4 ≈ 291 ft; or using d = V²/30f ≈ 55²/(30×0.35) ≈ 288 ft; closest answer ≈ 264 ft using d = V²/2a properly.
Question 4: In traffic flow theory, the Greenshields linear speed-density model assumes that speed decreases linearly from free-flow speed (uf) to zero as density increases from 0 to jam density (kj). The maximum flow occurs at density:
- kj/2 (Correct answer)
- kj/3
- kj/4
- 2kj/3
Correct answer: kj/2
In the Greenshields model, maximum flow occurs at k = kj/2 (half the jam density), where u = uf/2.
Question 5: The warrant for a traffic signal based on MUTCD Warrant 1 (Eight-Hour Vehicular Volume) requires that the minimum vehicular volumes must be met for at least:
- 8 hours of an average day (Correct answer)
- 4 hours of an average day
- 12 hours of an average day
- 2 hours of an average day
Correct answer: 8 hours of an average day
MUTCD Warrant 1 requires the vehicular volume thresholds to be met during 8 hours of an average day to justify signal installation.
Question 6: A vertical curve connects a +3% grade to a −2% grade. The algebraic difference in grades (A) used to compute curve length is:
- 5% (Correct answer)
- 1%
- 3%
- 2%
Correct answer: 5%
A = |g2 − g1| = |−2 − (+3)| = 5%; the algebraic difference determines minimum curve length requirements.
Question 7: According to AASHTO, the minimum length of a crest vertical curve for a design speed of 60 mph based on stopping sight distance (SSD ≈ 570 ft) is computed using K-value. The K-value for 60 mph design speed on a crest curve is approximately:
- 151 (Correct answer)
- 114
- 84
- 61
Correct answer: 151
AASHTO Table 3-35 gives K = 151 for crest vertical curves at 60 mph design speed, used as L = K×A.
Civil Engineering PE Transportation and Traffic Engineering 3
A two-lane highway has a directional split of 60/40 and a PHF of 0.90.
The directional design hourly volume (DDHV) based on an AADT of 12,000 vpd and a K-factor of 0.10 is: