Original question written by FE Exam AI Prep from the public FE Civil exam specification. Before release, a solver model re-derived the answer twice from the question alone, without its answer key, and a critic model checked the result, and the arithmetic was re-run as an executable calculation. No licensed engineer reviews these questions. It is not an NCEES question and does not come from any NCEES practice exam. FE Exam AI Prep is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCEES.
Traffic Flow, Speed and Density: FE Civil practice problem 1
For the East Valley retaining wall replacement, a project engineer preparing a quality-control closeout uses the traffic stream relation with speed 75 mph and density 21 veh/mi. What flow rate is indicated?
- A1766 veh/hr
- B1969 veh/hr
- C2443 veh/hr
- D1575 veh/hr
Show the answer and worked solution
Answer: D — 1575 veh/hr
Worked solution
- Step 1. Use traffic flow relation
q = k v
q = 21(75) = 1575 veh/hr
Why the other choices are wrong
- Choice A
- This total runs roughly 12% over the true result without matching any specific arithmetic slip that can be traced through the stated numbers. Working the calculation directly means evaluating q = k * v = 21 * 75, which yields 1575 veh/hr.
- Choice B
- This total sits roughly 25% over the true result, and no single unit slip, sign flip, or misapplied factor in the given data reproduces it cleanly. The reliable path computes q = k * v = 21 * 75 directly from the stated values to reach 1575 veh/hr.
- Choice C
- This figure lands roughly 55% above the true result and cannot be traced to one clean computational misstep in the values given. The dependable calculation evaluates q = k * v = 21 * 75 to arrive at 1575 veh/hr.