FE Civil Practice Question Solution included after investigation
CASE E-104 · FE

The Curve That Needed 833 ft, Not 1,190

The design speed was correct, but superelevation was omitted. Including both superelevation and side friction reduced the required curve radius to about 833 ft.

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Case E-104 engineering failure visual
HOW THIS WORKS

Think like
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Follow the investigation process used in the field — in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

2

Commit

Choose your hypothesis.

3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

Sign Off

See the full debrief and key takeaways.

Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

A roadway horizontal curve is designed for V=50 mph with superelevation e=0.06 and side-friction factor f=0.14. Using R=V²/[15(e+f)] with R in feet, determine the minimum curve radius. A note omits superelevation and reports about 1,190 ft.

Transportation Engineering Civil Design Verification Root Cause Analysis Safe Correction
E-104
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
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CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What failed

Superelevation was omitted.

What was missed

Roadway banking contributes to lateral-force balance.

Corrected model

Use R=V²/[15(e+f)] for the stated USCS relation.

QUICK ANSWER

R=50²/[15(0.06+0.14)]=833.3 ft. Omitting e would give about 1,190.5 ft.

ENGINEERING TAKEAWAY

Use both superelevation and side friction in the stated USCS relation R=V²/[15(e+f)].

CASE QUESTIONS

Questions this case should settle.

What terms are combined in the stated horizontal-curve radius formula?

Superelevation e and side-friction factor f.

NEXT FE PRACTICE QUESTION

The PM Peak That Sent 199 Cars In, Not 306

Transportation Engineering · 5–10 min

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WHAT YOU’LL LEARN

Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?

Basic subject familiarity helps, but every case is designed to teach through the investigation itself.

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Are the cases aligned with engineering exams?

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What happens after I complete a case?

The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.