Driver's License Test Prep
US Road Signs Road Markings

A broken white line separates your lane from the lane to your left, both traveling in the same direction. What does this marking permit?

A single broken white dashed line running lengthwise down a dark roadway.
  1. A.
    Lane changes across the line when it is safe to do so. Correct
  2. B.
    Passing by crossing into oncoming traffic.
  3. C.
    Crossing only in an emergency.
  4. D.
    Nothing; the line must not be crossed.
The Why

The answer is "Lane changes across the line when it is safe to do so."

A broken white line divides lanes moving the same way, and a driver may cross it to change lanes whenever the move is safe: signal, check mirrors and blind spots, then move over. The choice about passing into oncoming traffic reaches for the rule that governs broken yellow center lines on two-way roadways; broken white never sits between opposing lanes and has nothing to do with oncoming vehicles.

Why the others miss

The traps in the wrong answers

B. Passing by crossing into oncoming traffic.

Applies the broken-yellow passing rule for two-way roadways to a broken white line that only ever sits between same-direction lanes. This answer carries the broken-yellow passing rule across to a marking that never divides opposing traffic.

C. Crossing only in an emergency.

Treats the broken white line as a restricted marking, when it is the standard interior line drivers cross routinely to change lanes. This answer reads the broken pattern as an exception rule rather than the everyday interior lane line.

D. Nothing; the line must not be crossed.

Confuses the broken white line with a solid white line that discourages crossing between same-direction lanes. This answer applies the no-cross treatment of a solid white marking to a line whose broken pattern signals the opposite.

The Rule

This question tests your knowledge of Road Markings on the roads of every US state . Source: Manual on Uniform Traffic Control Devices, marking 3B.04 (Broken White Lane Line)..

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