Driver's License Test Prep
Pennsylvania Practice Warning Signs

A LOW CLEARANCE sign posts the height of an underpass. What does the manual tell you to do?

  1. A.
    Do not enter if your vehicle is taller than the listed height Correct
  2. B.
    Turn on your headlights before entering the underpass
  3. C.
    Slow to a crawl before passing beneath the underpass
  4. D.
    Sound your horn as you pass under the low clearance
The Why

The answer is "Do not enter if your vehicle is taller than the listed height"

The manual instructs you not to enter if your vehicle is taller than the height listed on the sign. Drivers still carrying the old tunnel-headlight rule tend to pick B, but LOW CLEARANCE is strictly a height limit and the sign carries no instruction about lights.

Why the others miss

The traps in the wrong answers

B. Turn on your headlights before entering the underpass

Headlights are not what a LOW CLEARANCE sign is telling you about; it posts the maximum vehicle height. This answer blurs the work-zone or tunnel headlight habit into any sign posted before a covered stretch of road.

C. Slow to a crawl before passing beneath the underpass

Low clearance is a height restriction, not a speed rule for the underpass. This answer treats every diamond-shaped warning sign as a speed-adjustment cue and misses the vehicle-fit meaning.

D. Sound your horn as you pass under the low clearance

The manual does not tie this sign to horn use; it is a limit on vehicle height. This answer carries over an older tunnel-etiquette habit of horn use that has nothing to do with a height-restriction sign.

The Rule

This question tests your knowledge of Warning Signs in Pennsylvania. Source: Pennsylvania Driver Manual, "LOW CLEARANCE," p.16..

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