FE Civil · Chapter 14 · 8–12 exam questions

FE Civil Transportation Eng.

This chapter covers highway geometric design, traffic engineering, travel demand planning, traffic control devices, flexible and rigid pavement design, and earthwork calculations.

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What the FE tests in Transportation Eng.

Geometric Design

As a civil engineer, you design roads that let drivers see far enough to stop safely, transition smoothly between grades on vertical curves, and navigate horizontal curves at the design speed with proper superelevation. These geometric elements control safety, cost, and right-of-way requirements.

Traffic Engineering

As a civil engineer, you time traffic signals to balance safety and efficiency, analyze traffic flow using the Greenshields model, evaluate freeway capacity and level of service, and measure crash rates to compare safety performance across locations.

Planning & Traffic Operations

As a civil engineer, you forecast travel with the four-step model and distribute trips between zones using the gravity model, and you apply the MUTCD to select signs, markings, and signals — installing a signal only when a warrant is met. These planning and operations tasks shape demand and safety before and after a road is built.

Pavement Design & Earthwork

As a civil engineer, you design flexible pavement sections using the AASHTO structural number equation, design rigid (concrete) slabs that carry load by beam action, convert mixed axle loads to ESALs, and compute earthwork volumes between cross sections to estimate cut-and-fill quantities for highway construction.

Key Transportation Eng. formulas

$SSD = 1.47 V t + \frac{V^2}{30\left(\frac{a}{32.2} \pm G\right)}$
Stopping Sight DistanceFE Handbook p. 300
$L = \frac{A S^2}{2{,}158}$
Crest Vertical Curve (S ≤ L)FE Handbook p. 302
$R = \frac{5{,}729.58}{D}$
Horizontal Curve RadiusFE Handbook p. 302
$y = t + \frac{v}{2a \pm 64.4G}$
Yellow Signal IntervalFE Handbook p. 300
$V_m = \frac{D_j S_f}{4}$
Maximum Flow (Greenshields)FE Handbook p. 306
$v_p = \frac{V}{PHF \times N \times f_{HV}}$
Demand Flow RateFE Handbook p. 305
$SN = a_1 D_1 + a_2 D_2 m_2 + a_3 D_3 m_3$
AASHTO Structural NumberFE Handbook p. 308
$V = \frac{L(A_1 + A_2)}{2}$
Average End Area VolumeFE Handbook p. 309
$T_{ij} = P_i \frac{A_j F_{ij} K_{ij}}{\sum_j A_j F_{ij} K_{ij}}$
Gravity Model (Trip Distribution)FE Handbook p. 306

Sample Transportation Eng. problems

Q1. A designer is computing SSD for a road with a $6\%$ upgrade. Compared to a level road at the same design speed, what happens to the SSD?

Answer: SSD decreases because gravity assists braking on an uphill grade

Explain it simply

On an uphill grade, gravity pulls the vehicle backward, helping the brakes slow it down. In the formula, a positive $G$ makes the denominator $30(a/32.2 + G)$ larger, which makes the braking distance fraction smaller. The reaction distance is unchanged (grade does not affect perception-reaction time), but the braking distance is shorter. Choice A reverses the effect of uphill. Choice C ignores the grade term entirely. Choice D wrongly claims grade affects reaction time.

Q2. When computing the minimum length of a sag vertical curve, the headlight criterion is used instead of the driver eye height criterion used for crest curves. Why?

Answer: On a sag curve at night, the line of sight is not blocked by the road surface -- the limiting factor is how far the headlights illuminate the road ahead

Explain it simply

On a crest curve, the road surface itself blocks the driver from seeing objects beyond the hill -- so the sight distance depends on eye height and object height. On a sag curve, you can see over the valley during the day with no obstruction. But at night, you can only see as far as your headlights illuminate. The headlight beam angle (about 1 degree upward) and the mounting height determine how far down the sag the beam reaches. Choice A is wrong because sag curves are not always shorter. Choice C is incomplete -- it only addresses daytime. Choice D is wrong because the nighttime case governs the design.

These are 2 of 1,126 problems across all 15 chapters. The full bank, lessons, mastery tracking, and timed exam simulation live inside the app.

Common Transportation Eng. mistakes on the FE

SSD grade sign: uphill (+G) = shorter SSD, downhill (−G) = longer SSD. Students often reverse this.
Crest vs. sag vertical curve formulas have different denominators — 2,158 for crest, (400 + 3.5S) for sag.
Yellow interval uses v in ft/sec, not mph — multiply mph by 1.467 to convert.
LOS is determined by DENSITY, not by volume or speed. Compute D = vp/S first.
Average end area always overestimates compared to prismoidal — don't confuse the two.
In the gravity model, normalize by the sum over ALL destination zones, and remember the friction factor falls as travel time rises.
Rigid pavement carries load by slab/beam action (depends little on subgrade); flexible spreads load through its layers (structural number).
Dowel bars transfer load across joints while allowing movement; tie bars hold joints closed — they are not the same.
A traffic signal needs a satisfied MUTCD warrant — an unwarranted signal can increase rear-end crashes and delay.

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