Collection: Road Warning Signs

Road warning signs are the yellow diamond-shaped signs that alert drivers to upcoming road conditions, hazards, or changes. They are defined in the MUTCD W-series and cover curves, turns, intersections, pedestrian crossings, speed advisories, lane transitions, and road surface conditions.

Warning signs are not regulatory. They do not impose a legal requirement like a stop or speed limit sign. They advise drivers to adjust speed or behavior based on what is ahead. All warning signs in this collection are manufactured to MUTCD specifications for shape, color, legend, and reflectivity. For the full list of MUTCD warning sign standards, see MUTCD Part 2C.

We offer four sheeting options on most warning signs. All four exceed the MUTCD minimum reflectivity requirement for permanent warning sign installations.

High Intensity Prismatic (HIP) meets ASTM D4956 Type IV. Uses truncated cube technology. This is the standard choice for most permanent warning signs on conventional roads.

Diamond Grade (DG3) meets ASTM D4956 Type XI. Uses full-cube prismatic technology that returns nearly twice the light of HIP. Best for high-speed roads, poorly lit areas, or locations where maximum driver reaction time is critical.

Diamond Grade Fluorescent Yellow uses the same full-cube DG3 technology as standard Diamond Grade, but adds a fluorescent yellow pigment for significantly better visibility during dawn, dusk, and overcast conditions. It meets all MUTCD color specifications for yellow warning signs. Choose this when you want both premium nighttime reflectivity and enhanced daytime conspicuity.

Diamond Grade Fluorescent Yellow Green is a distinct color required by the MUTCD for signs warning of non-motorized traffic. This includes pedestrian crossing signs (W11-2), bicycle crossing signs (W11-1, W11-15), and school zone signs (S1-1). It is not interchangeable with standard yellow. If your sign falls into one of these categories, fluorescent yellow green is the correct choice.

The MUTCD specifies warning sign sizes based on road type:

• Conventional roads: 30" x 30"
• Freeways and expressways: 36" x 36" (minimum) to 48" x 48"
• Low-speed, low-volume roads (25 mph or less): 24" x 24" minimum

Advisory speed plaques and supplemental plaques are smaller and mount below the parent sign. Standard plaque size is 24" x 18" on conventional roads.

Most municipalities and contractors purchase 30" x 30" for standard two-lane roads and 36" x 36" for multi-lane or higher-speed applications. For the full MUTCD warning sign size table, see Table 2B-1.

Replace any sign that is faded, cracked, peeling, bent, or no longer reflective at night. A sign that looks fine during the day can fail completely after dark. The FHWA recommends inspecting all warning signs at least once per year, including a nighttime check to verify retroreflectivity.

Common reasons for replacement:

• Fading or discoloration from UV exposure
• Cracking or separation of the reflective surface
• Bending from impacts or wind damage
• Salt spray or chemical buildup that dulls reflectivity
• Vandalism, bullet holes, or paint overspray

Do not remove a damaged sign and leave the location empty. The FHWA recommends keeping a replacement on hand so a damaged sign can be swapped immediately. For detailed inspection procedures and field repair guidance, see the FHWA Guide for Street and Highway Maintenance Personnel.