Driver's License Test Prep
US Road Signs Warning Signs

What does this Reduced Speed Limit Ahead sign require of a driver?

Yellow diamond with a black upward arrow above a small white SPEED LIMIT 45 plaque
  1. A.
    Begin slowing so your speed is at or below the new limit by the regulatory sign that follows. Correct
  2. B.
    Immediately drop to the value shown the moment you pass this sign.
  3. C.
    Slow only if current road conditions make the posted limit unsafe.
  4. D.
    Hold current speed until you reach the new regulatory speed-limit sign.
The Why

The answer is "Begin slowing so your speed is at or below the new limit by the regulatory sign that follows."

This sign is advance notice. Begin slowing now so your speed is at or below the new limit by the time you reach the regulatory sign that actually posts it. The trap is the choice that says drop to the shown value the moment you pass the diamond. That reads the yellow warning as if it were the black-on-white regulatory posting, but a yellow diamond never sets the enforceable limit; the regulatory sign that follows does.

Why the others miss

The traps in the wrong answers

B. Immediately drop to the value shown the moment you pass this sign.

The new limit becomes enforceable only where the regulatory sign is posted; this diamond simply flags what is coming. Reads the diamond as the enforceable posting and cuts speed the moment the driver reaches it.

C. Slow only if current road conditions make the posted limit unsafe.

A reduced-limit warning applies regardless of conditions; the new legal limit will take effect at the regulatory sign. Mistakes the diamond for an advisory plaque whose number kicks in only when weather or pavement warrant.

D. Hold current speed until you reach the new regulatory speed-limit sign.

The purpose of the advance sign is to let you slow gradually before the new limit is posted, not to authorize holding the old speed. Waits for the regulatory posting instead of using the warning to bleed off speed early.

The Rule

This question tests your knowledge of Warning Signs on the roads of every US state . Source: Manual on Uniform Traffic Control Devices, sign W3-5 (Reduced Speed Limit Ahead)..

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