Official MUTCD W8-5 Slippery When Wet Signs

Reduce skidding accidents and warn drivers of low-traction conditions with Federal Slippery When Wet Signs. We stock the official W8-5 Symbol warning diamond required for slick bridges, curved ramps, and oil-slicked surfaces. Manufactured with rain-resistant Diamond Grade or High Intensity Prismatic reflectivity, our Slippery When Wet Signs provide the critical advance warning needed to prevent loss of vehicle control during storms.
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Placement for Slippery Conditions (MUTCD 2C.32)

The W8-5 Slippery When Wet sign must be placed strategically to allow drivers to slow down before they lose traction.

  • Advance Placement: Install the sign 500 feet in advance of the slippery section or curve on rural highways. This provides adequate perception-reaction time for drivers to lift off the throttle without sudden braking (which can induce a skid).
  • Curve Assembly: For specific slippery curves, mount the W8-5 sign directly above a yellow Advisory Speed Plaque (W13-1P) (e.g., 35 MPH) to indicate the safe wet-weather speed.
  • Continuous Hazard: For long stretches of polished pavement, pair the sign with a "NEXT X MILES" plaque to keep drivers alert.

Federal Standards for Road Surface Condition Signage

Loss of traction is a leading cause of roadway departures and head-on collisions. Slippery When Wet Signs are the primary engineering countermeasure used to alert drivers that the pavement friction coefficient drops significantly during rain or damp conditions. Under MUTCD Section 2C.32, installing Slippery When Wet Signs is often mandatory where there is a documented history of wet-weather crashes or where pavement tests show "polished" aggregate.

The W8-5 Skidding Car Symbol

The modern standard for Slippery When Wet Signs is the W8-5 symbol.

  • The Icon: Features a black silhouette of a car with "swerving" tire tracks behind it on a yellow background. This pictogram is universally recognized and processes faster than text-based signs during high-stress driving situations.
  • Text Option: While the "SLIPPERY WHEN WET" (W8-5a) text sign is still compliant in some jurisdictions, the Symbol version is the preferred federal standard for all new installations.

Placement & Advisory Speeds

Slippery When Wet Signs are most effective when paired with specific actionable instructions.

  • Advisory Speed Plaques (W13-1P): If the safe speed for a wet curve is lower than the posted limit, you must mount a yellow Advisory Speed Plaque (e.g., "35 MPH") directly below the Slippery When Wet Sign.
  • Distance Plaques: For long stretches of polished pavement, use a "NEXT 5 MILES" plaque to keep drivers alert.
  • Placement: Install the sign 500 feet in advance of the slick area on rural highways to allow for gradual deceleration without braking (which causes skids).

Reflectivity for Storm Visibility

Slippery When Wet Signs are only needed when conditions are bad—heavy rain, fog, or spray.

  • The "Water Film" Problem: Standard sign sheeting can "wash out" or lose reflectivity when covered in a sheet of water.
  • Diamond Grade Solution: We strongly recommend Type XI Diamond Grade sheeting for all Slippery When Wet Signs. Its micro-prismatic structure is designed to maintain luminance even when wet, ensuring the warning cuts through the storm.

Specific Hazards: Bridges & Fresh Oil

  • Steel Deck Bridges: Metal grates become ice-like when wet. Slippery When Wet Signs are mandatory at the bridge approaches.
  • Fresh Oil / Chip Seal: During resurfacing, loose gravel and oil create slick conditions. Temporary orange Slippery When Wet Signs are used here until the surface cures.

Frequently Asked Questions

Common questions regarding MUTCD compliance, installation standards, and material specifications for regulatory signage.
When is a "Slippery When Wet" sign required?

Engineering studies often dictate the need based on the Skid Number (friction coefficient) of the asphalt. If the pavement is worn smooth (polished) or has an excess of asphalt binder ("bleeding"), Slippery When Wet Signs must be posted until the road can be resurfaced to restore traction.
What is the difference between "Slippery When Wet" and "Watch for Ice"?

Slippery When Wet Signs (W8-5) refer specifically to rain/water hazards. Bridge Ices Before Road (W8-13) is a seasonal warning for frost. Using the wrong sign can confuse drivers about the nature of the hazard.
Can I put this sign on a steep driveway?F

Yes. Private property owners with steep, paved driveways often install Slippery When Wet Signs to warn delivery trucks and guests. On private land, this reduces liability if a vehicle slides off the driveway during a rainstorm.

Need specific code assistance?

If your project requires a specific State DOT certification or a specialized variation not listed here, please contact our Compliance Support Team for a custom specification sheet.