What is the difference between AASHTO M247 Type I and Type III glass beads?

Type I beads are smaller (600-2,000 microns) and used for most parking-lot and city-street markings. Type III beads are larger (1,200-2,800 microns) and used for highway lane lines where deeper bead embedment in higher-build thermoplastic provides longer retroreflectivity life. Type I is the right choice for almost all parking-lot work.

How many pounds of beads should be dropped per linear foot of 4-inch line?

At 8-12 lb per 100 square feet AASHTO M247 spec, a 4-inch line carries approximately 0.027 to 0.040 lb of beads per linear foot, or 2.7 to 4.0 lb per 100 LF. At 9 lb per 100 sq-ft median, that's about 3 lb per 100 LF of 4-inch line.

Why do glass beads cost so much in 2026?

US glass-bead supply is mostly imported from China and Vietnam. Mid-2025 freight surcharges added 9 percent to landed prices and EPA reformulation guidance pushed manufacturers to remove residual heavy metals from older bead stock, both of which contributed to 2026 pricing climbs. Type I bulk pricing landed at $0.85-$1.05 per lb in Pacific Northwest in Q1 2026.

Can the contractor use a different bead type to save money?

No. AASHTO M247 Type I is the spec for parking-lot work. Substituting smaller non-spec beads (under 600 microns) produces markings with poor retroreflectivity. Substituting larger non-spec beads creates loose-bead problems. The Type I spec is what state DOT QPLs reference and what manufacturer data sheets call out for proper retroreflectivity performance.

How do I tell if my markings have proper bead drop?

Visually: at night with low-angle light (a flashlight held about 18 inches above pavement at 10-degree angle from the marking), the line should glow visibly. If the glow is dim or absent, the bead drop was insufficient or beads have already worn off. A retroreflectometer reading is the definitive test; readings below 100 mcd/m2/lx for white indicate maintenance restripe is due.

Thermoplastic Glass Bead Drop Rate: AASHTO M247 Spec Guide

(541) 409-9848 cojoexcavation@gmail.com

Serving Eugene to Portland, Bend, and the Oregon Coast

The AASHTO M247 standard specifies the glass beads used to provide retroreflectivity on thermoplastic pavement markings. Type I drop-on beads at 8 to 12 lb per 100 square feet of marking area is the standard spec for parking-lot and most state-highway applications. Beads embed roughly 60 percent into still-molten thermoplastic resin and reflect headlight beams back toward drivers, producing the visible glow that makes nighttime markings readable. Initial retroreflectivity targets are 250 mcd/m2/lx for white and 175 for yellow per AASHTO PP-65, measured with a 30-meter geometry retroreflectometer. Beads must be dropped within 5 seconds of resin landing for proper embedment.

Bead drop rate is one of the most commonly under-specified line items in thermoplastic quotes. A contractor that delivers AASHTO M249 thermoplastic but skimps on bead rate (5-6 lb per 100 sq-ft instead of 8-12) produces markings that look fine in daylight and fail retroreflectivity at night within months. Below we break down the spec, the bead types, drop-rate variations by application, and how to verify a contractor is actually delivering the right material.

What is AASHTO M247?

AASHTO M247 is the standard specification for glass beads used in pavement marking materials. It defines:

Bead types (Type I through Type V) by size grading
Refractive index (1.50 minimum for Type I)
Roundness (70 percent minimum spheres)
Moisture content (0.05 percent maximum)
Sieve grading (specific micron-size distribution per type)
Coating (silicone or proprietary moisture-resistant treatment)

Type I beads (the most common) have a size range of approximately 600-2,000 microns (0.024 to 0.079 inches) with the bulk of the distribution in the 850-1,200 micron range. Type III and Type IV are larger beads (up to 2,800 microns) used for high-build markings on highway lane lines where the larger beads embed deeper and last longer.

Why do thermoplastic markings need glass beads?

Thermoplastic pavement markings reflect light back to drivers through retroreflectivity provided by spherical glass beads embedded in the marking surface. Headlight beams hit the curved surface of an embedded bead, refract through the glass, reflect off the back of the bead's embedment in the resin, and re-emerge back toward the driver. The geometry produces visible glow at distances of 100-400 feet ahead of a vehicle.

Without beads, a thermoplastic marking is matte and produces almost no nighttime visibility. A vehicle's headlights at low-beam typically cannot resolve a non-reflectorized line at 200+ feet, which is the practical safe-stopping distance at 35 mph.

What is the drop rate spec for parking lots?

For parking-lot thermoplastic markings, the standard drop rate is 8 to 12 lb of AASHTO M247 Type I beads per 100 square feet of marking area. State DOT specifications can be stricter:

Oregon DOT: 8 lb per 100 sq-ft minimum on QPL parking-lot products
California Caltrans: 9 lb per 100 sq-ft
Texas DOT: 10 lb per 100 sq-ft on highway lane lines
Federal AASHTO baseline: 8 lb per 100 sq-ft

A 4-inch wide line carries approximately 33.3 square feet per 100 LF, so the bead drop adds ~3.0-4.0 lb per 100 LF of 4-inch line. At Type I bead bulk price of $0.75-$1.20 per lb, that's $2.25-$4.80 per 100 LF in bead material alone, or $0.02-$0.05 per LF.

Industry baseline range bead pricing

Industry Baseline Range

Bead Type	Use	Range per lb (bulk wholesale)
AASHTO M247 Type I	Parking lots, standard markings	$0.65 to $1.30
AASHTO M247 Type III	Highway lane lines	$0.95 to $1.85
AASHTO M247 Type IV (large)	High-vis lane lines, edge lines	$1.20 to $2.40
Indium-coated beads (premium retroreflectivity)	Specialty high-spec work	$2.50 to $5.00

These figures reflect published industry averages. Current market pricing varies significantly and actual quotes may fall well outside these ranges based on site-specific conditions, material costs, and project complexity.

Current Market Reality

2026 glass-bead pricing climbed roughly 9 percent over 2024 due to mid-2025 freight surcharges from Asian manufacturers (most US bead supply is imported from China and Vietnam) plus EPA reformulation guidance that pushed manufacturers to remove residual heavy metals from older bead stock. The Q1 2026 Cojo supply chain saw Type I bulk pricing at $0.85-$1.05 per lb landed in Pacific Northwest. Smaller-bag retail (5-gallon pail equivalent) runs higher per-lb because of packaging cost.

What about intermixed beads?

Thermoplastic resin includes pre-mix glass beads (intermixed at 30-40 percent by weight inside the resin pellet). These are smaller beads (typically 100-600 microns) that get exposed as the surface wears down. Intermixed beads are baked into AASHTO M249 resin and do not require separate specification.

The drop-on beads (8-12 lb per 100 sq-ft) are what provide initial retroreflectivity until tire wear exposes the intermixed beads. The two layers work together: drop-on beads carry the marking from day 1 to roughly year 2-3, then intermixed beads take over as wear progresses.

How is drop rate verified in the field?

Three methods:

Visual inspection -- A properly bead-dropped marking shows visible bead embedment when light hits it at low angle. Loose beads on the surface (not embedded) indicate either resin chilled too fast or drop rate exceeded what the resin could absorb.
Retroreflectometer reading -- 30-meter geometry retroreflectometer per AASHTO PP-65 measures retained retroreflectivity (RL) in mcd/m2/lx. Initial readings should hit 250+ for white and 175+ for yellow.
Pound-rate calculation -- Drop-on bead weight from job-site delivery records divided by marking area covered. Should land in the 8-12 lb per 100 sq-ft window.

State-DOT-funded projects typically require retroreflectometer readings as part of the final inspection. Private parking-lot work usually does not but spot-checks can be requested.

What happens when the drop rate is too low?

Below 8 lb per 100 sq-ft drop rate produces:

Initial retroreflectivity below the 250 mcd/m2/lx target for white
Marking appears dimmer at night even when fresh
Premature loss of retroreflectivity as the few beads present wear off
AASHTO M247 spec failure in field testing

Some contractors deliberately under-drop beads to lower material cost. The savings is typically $0.02-$0.04 per LF of line work. The trade-off is markings that fail retroreflectivity 18-30 months earlier than properly bead-dropped markings, which forces repaint or restripe months ahead of schedule.

What happens when the drop rate is too high?

Above 12 lb per 100 sq-ft drop rate produces:

Loose beads on the surface that bounce off and end up in adjacent pavement texture
Wasted material cost (over-drop beads do not embed)
Slight initial retroreflectivity gain that does not justify the material cost
No long-term durability advantage

Most reputable contractors target 9-10 lb per 100 sq-ft as the sweet spot: comfortably above the 8 lb minimum, well below the 12 lb diminishing-returns ceiling.

How does Cojo specify the drop rate?

Cojo standard practice on parking-lot installs:

9 lb per 100 sq-ft AASHTO M247 Type I drop-on beads (median of the spec window)
6-second drop window from resin landing (within the 5-second minimum but allowing equipment ramp time)
Job-site delivery records stored in the project file for verification
Retroreflectometer reading on first 5 percent of completed work to verify initial RL

State-DOT-funded work bumps drop rate to 10-12 lb per 100 sq-ft per the project specification. Private retail and HOA work runs at 9 lb standard.

How should buyers verify drop rate compliance?

Ask the contractor for:

AASHTO M247 Type I (or Type III for highway work) bead specification on the quote
Drop-rate target (lb per 100 sq-ft) line-itemed
Job-site bead delivery records (weight delivered vs marking area completed)
Optional: retroreflectometer reading on completed work

A quote that says only "thermoplastic with glass beads" without rate specification is incomplete. Push back for a specific lb-per-100-sq-ft target.

For service-side context on Oregon-specific specifications, see our thermoplastic striping Oregon writeup. For full install-process detail, our how to apply thermoplastic pavement markings walks through the bead-drop step in context.

Get a Spec-Compliant Bead-Dropped Thermoplastic Install

Cojo runs AASHTO M247 Type I beads at 9 lb per 100 sq-ft minimum on every parking-lot install, with delivery records and retroreflectometer verification on request. Contact Cojo for a thermoplastic quote with bead-rate compliance built in. For Portland service availability, see our thermoplastic installation Portland Oregon page.

Thermoplastic Glass Bead Drop Rate: AASHTO M247 Spec Guide