The federal specification for snowplowable raised pavement markers is ASTM D4280, Type H -- the high-impact category that covers markers rated to survive contact with snowplow blades. This guide walks through the spec, the carrier materials it allows, the install procedure, and how it interacts with FHWA retroreflectivity guidance.
What is ASTM D4280?
ASTM D4280 is the standard specification for extended-life retroreflective raised pavement markers. It covers:
- Body dimensions and tolerances
- Lens retroreflectivity at standard observation angles
- Adhesive bond strength under controlled conditions
- Impact resistance categories
- Lifecycle and weatherability requirements
The standard is maintained by ASTM International and used by federal, state, and local transportation agencies as the baseline specification for retroreflective RPMs in public-road and parking-lot applications.
What is Type H?
ASTM D4280 categorizes markers by impact resistance:
| Type | Description |
|---|---|
| Type A | Standard retroreflective, no impact rating |
| Type B | Standard retroreflective with impact category |
| Type C through F | Variations on body and adhesive performance |
| Type H | High-impact -- snowplow rated |
Cast-iron vs polymer carrier
Type H rating is achieved most commonly with a cast-iron carrier and a recessed lens, but the spec does not mandate cast iron specifically. Two carrier approaches:
Cast-iron carrier (dominant)
- Carrier deflects plow blade
- Lens recessed inside carrier; protected from blade contact
- Mechanically anchored to substrate
- Service life 7 to 12 years for the carrier
- Lens field-replaceable in most designs
High-modulus polymer carrier (rare)
- Carrier flexes under blade contact rather than deflecting
- Lens recessed
- Mechanically or chemically anchored
- Service life 5 to 8 years
- Used in specialized applications where cast iron is impractical
For most parking-lot installs, the cast-iron carrier is the right specification.
Carrier dimensions
Typical Type H carrier dimensions:
| Dimension | Range |
|---|---|
| Carrier length (along travel direction) | 5 to 7 inches |
| Carrier width (across travel direction) | 4 to 5 inches |
| Carrier height above pavement | 0.0 to 0.2 inches |
| Lens recess depth | 0.1 to 0.3 inches below carrier face |
| Anchor depth into substrate | 1 to 2.5 inches |
Recess install procedure
The Type H install differs from standard raised marker install in three steps:
Pocket milling
A pocket is milled into the asphalt or concrete to receive the carrier. The pocket is sized to match the carrier footprint plus a small clearance for adhesive. Pocket depth places the carrier face flush with or slightly above the surrounding pavement.
Mechanical anchor placement
The carrier includes integral mechanical anchors -- bolts, expansion plugs, or rebar pins -- that drop into pre-drilled holes in the pocket bottom. This locks the carrier to the substrate at depth.
Epoxy bedding
2-part epoxy per ASTM C881 Type V is poured into the pocket around the anchors. The carrier is set into the wet epoxy and pressed into final position. Cure time 4 to 8 hours.
For full install procedure see how to install raised pavement markers and pavement marker adhesive selection.
Lens retroreflectivity requirements
Type H lenses must meet the same retroreflectivity baseline as standard ASTM D4280 lenses. The baseline is measured in millicandelas per lux per square meter (mcd/lux/m^2) at standard observation angles. FHWA publishes minimum maintained retroreflectivity in its retroreflectivity policy.
Some Type H designs sacrifice a small amount of off-axis brightness for the recessed pocket geometry. Microprism lens designs compensate for this with higher peak retroreflectivity.
Plow-blade contact test
ASTM D4280 specifies a plow-blade contact test for Type H qualification:
- Marker is installed in a test pavement
- A simulated plow blade contacts the carrier at a specified angle and load
- The marker must survive a defined number of contacts without:
Manufacturers document the test results in the technical data sheet for each Type H product.
Real Cojo install reference
For a 22,000-square-foot Bend retail center in October 2025, we installed 188 ASTM D4280 Type H snowplowable markers across the main lane lines and entry-exit drives. Carrier was ductile iron; lens was two-way replaceable polycarbonate. Mechanical anchors were 1.5-inch expansion plugs in pre-drilled 1.75-inch deep holes; bedding was 2-part epoxy per ASTM C881 Type V. After the 2025-2026 winter, all 188 carriers were intact; 184 of 188 lenses retained target retroreflectivity. The 4 lenses showing scuff damage were field-replaced for $32 total in lens cost.
FHWA retroreflectivity guidance
The FHWA Methods for Maintaining Pavement Marking Retroreflectivity policy establishes minimum maintained retroreflectivity levels for pavement markings on federal-aid highways. Type H markers are typically specified at or above these minimums to provide a multi-year buffer before replacement is required.
Type H on parking lots
Parking-lot specs do not require Type H by federal mandate. Property managers select Type H when:
- The lot is mechanically plowed
- Annual snowfall exceeds 12 inches
- The lot sees ice scraping or aggressive winter maintenance
- A 5-plus year service interval is desired
For non-plowed lots in Willamette Valley climate, standard ASTM D4280 (non-Type-H) markers are appropriate at lower cost.
Replacement lens compatibility
Most Type H carriers accept the manufacturer's standard replacement lens module. Cross-manufacturer compatibility is not guaranteed; specifying a single manufacturer for a lot's carriers preserves the simple field-replacement workflow.
For full snowplowable spec see snowplowable vs standard pavement markers and product picks at best snowplowable pavement markers 2026.