Warning Road Sign (W1-4)
Reverse Curve Ahead Sign Meaning & Driving Rules
Warns of two consecutive gradual curves in opposite directions, separated by a tangent distance of less than 600 feet.
Required Driver Action & Right-of-Way Protocol
Slow down before the first curve. Guide the vehicle smoothly through both bends without abrupt steering corrections.
Detailed Overview & Purpose
The Reverse Curve sign (W1-4) warns of an S-shaped road alignment consisting of two gradual curves bending in opposite directions. The first curve bends in the direction indicated by the bottom of the arrow.
Smooth steering transition at the midpoint is essential to avoid body roll and weight transfer that can destabilize the vehicle, particularly for high-profile vehicles like SUVs and commercial trucks.
Advisory speed plaques are frequently mounted below this sign to communicate the maximum safe speed for negotiating the dual-curve geometry.
Key Standard & Origin: Smooth S-curves can induce vehicle rollover in top-heavy vehicles if weight shifts too violently from side to side during the steering transition.
Where You'll Find This Sign
Rural highways, scenic drives, and parkway corridors following natural terrain contours.
Common Driver Mistakes to Avoid
Over-steering during the center transition between curves, causing the vehicle to fishtail or slide on wet or gravel-strewn surfaces.
How This Sign Appears on the DMV Knowledge & Road Test
Appears on knowledge exams testing road geometry and steering weight balance.
Legal Penalties and Moving Violations
Failure to maintain single lane in curves results in moving violation citations.
Sign Variations & Related Types
Reverse Curve Right-Left (W1-4R)
First curve is to the right, second curve is to the left.
Reverse Curve Left-Right (W1-4L)
First curve is to the left, second curve is to the right.
When you encounter the official Reverse Curve Ahead (W1-4) on a roadway, what is your legal duty?
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