Federal Motor Vehicle Safety Standard No. 205, codified at 49 CFR 571.205, sets the federal requirements for every piece of glass installed in a motor vehicle sold in the United States. The rule governs how automotive glazing is built, tested, and marked; where each type of glass can be installed on a vehicle; and what light transmittance it must allow. It applies to new vehicles at the factory and to replacement glass installed years later, and it carries civil penalties measured per piece of glass.1eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials
Which Vehicles and Which Glass Are Covered
The standard covers passenger cars, multipurpose passenger vehicles, trucks designed to carry at least one person, buses, motorcycles, slide-in campers, pickup covers designed to carry people while moving, and low-speed vehicles such as neighborhood electric vehicles and golf carts.1eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials On those vehicles, every glazing component is regulated: windshields, side windows, rear windows, sunroofs, and interior partitions.
The technical benchmarks for impact resistance, fragmentation, optical quality, and durability come from the ANSI/SAE Z26.1-1996 safety code, which FMVSS 205 incorporates by reference.1eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials Compliance with FMVSS 205 requires meeting those underlying tests.
AS Ratings and Where Each Type of Glass Can Go
Every piece of compliant automotive glass carries an “AS” rating. The rating dictates where on the vehicle the glass can legally be installed. Installing a piece of glass with the wrong rating in the wrong location violates federal law even if the glass itself is well made.
AS-1
AS-1 is the only rating approved for windshield use, and it can be installed anywhere else on the vehicle as well. AS-1 glass is laminated: two sheets of glass bonded to a plastic interlayer that holds fragments together on impact and helps keep occupants inside the vehicle during a crash. It must pass the most demanding tests for impact resistance, penetration resistance, and optical clarity.
AS-2
AS-2 glass is approved for every location except the windshield. Side and rear windows commonly use AS-2 tempered glass, which is heat-treated and breaks into small, relatively dull granules rather than jagged shards. AS-2 glass can also be laminated.
AS-3
AS-3 glass cannot be used in a windshield or in any window position needed for driving visibility. On passenger cars, that generally limits AS-3 to rear quarter panels and some rear windows. On trucks and buses, it can appear in positions behind the driver’s immediate left and right windows, provided those positions aren’t relied on for driving visibility. AS-3 is typically tinted, which is why it is often called privacy glass.
AS-4 and Item 4A
AS-4 glazing is permitted for windshields on low-speed vehicles, which are generally capped at 25 mph.1eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials Item 4A glazing can be used for side windows behind the C-pillar (the rearmost roof support).
The 70% Light Transmittance Rule
All glazing in areas needed for driving visibility, including the windshield and front side windows, must allow at least 70% of visible light to pass through.2National Highway Traffic Safety Administration. Interpretation 11-000697 – FMVSS No. 205 Glazing Materials If a windshield has no AS-1 shade band line marked on it, the entire windshield must meet that 70% threshold.
Behind the transmittance rule sits the broader ANSI/SAE Z26.1 test suite. Glass samples are struck with standardized projectiles to simulate road debris and interior head impacts. Laminated windshield glass must resist penetration by objects that would otherwise enter the cabin. Tempered glass must fragment into pieces within specified size limits. Samples are subjected to accelerated weathering and chemical exposure so that the glass doesn’t cloud, delaminate, or lose strength over time. These tests apply to original equipment and to any replacement glass installed later.
How to Read the DOT Marking on a Piece of Glass
Every compliant piece of automotive glass carries a permanent marking, usually etched or printed in one corner, that the industry calls a bug or monogram. Under Section S6 of the standard, a prime glazing manufacturer certifies its product by adding specific identifiers to the marks already required by ANSI/SAE Z26.1.3eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials – Section S6
A compliant bug includes the manufacturer’s name or trademark; the letters “DOT” followed by a code number that NHTSA assigns to the manufacturer after a written request confirming prime glazing manufacturer status; the AS rating for that piece of glass; and an M-number identifying the specific construction, coating, and thickness.1eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials The M-number’s meaning is known only to the manufacturer.
Before an installer finishes a replacement job, check the bug. A windshield should read AS-1 (AS-4 for low-speed vehicles). Glass with no bug at all is non-compliant and should be rejected. Missing or incorrect markings can cause a vehicle to fail a state safety inspection.
Replacement Glass and the “Make Inoperative” Rule
FMVSS 205 continues to apply after the vehicle leaves the dealership. Any glazing installed as a replacement must meet either the current version of FMVSS 205 or the version that applied when the vehicle was originally manufactured, whichever the replacement glazing is designed to satisfy, and it must carry proper DOT and AS markings.4eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials – Section S5.1.2 Used or salvage-yard glass is legal to install if it still bears the required markings and meets the applicable specifications.5eCFR. 49 CFR 571.205 – Standard No. 205, Glazing Materials
Under 49 U.S.C. § 30122, manufacturers, distributors, dealers, rental companies, and repair businesses are prohibited from knowingly making inoperative any device or design element installed to comply with a federal safety standard.6Office of the Law Revision Counsel. 49 USC 30122 – Making Safety Devices Inoperative For a glass shop, that means installing non-compliant tint on front windows, using unmarked glass, or placing AS-3 glass where AS-1 is required is a federal violation. A vehicle owner modifying a personal vehicle is not covered by that prohibition, though state law may still apply.
How State Tint Laws Fit
Federal preemption under 49 U.S.C. § 30103 prevents states from setting different standards for the manufacture and sale of new glazing or new vehicles. A state cannot authorize a manufacturer to sell windshields that fail the 70% transmittance test. NHTSA has confirmed, however, that states can permit the registration of a vehicle an owner has modified with aftermarket window tinting, even if that tinting drops light transmittance below 70%.7National Highway Traffic Safety Administration. Interpretation ID 17440 – FMVSS No. 205
That split explains why every state has its own tint law with different allowable percentages for different windows. The federal 70% floor governs what leaves the factory and what a repair shop can legally do; state law governs what an owner can drive on the road after making personal modifications. A professional installer who applies illegal tint may still face federal liability under the make-inoperative rule.
ADAS Calibration After a Windshield Replacement
Most vehicles built since roughly 2016 have a forward-facing camera mounted behind the windshield that powers automatic emergency braking, lane departure warnings, and adaptive cruise control. Replacing the windshield can shift that camera’s position enough to throw off the system’s calculations, causing emergency braking to activate without cause or fail to activate when needed.
As of 2026, no federal regulation specifically requires ADAS recalibration after a windshield replacement. Most vehicle manufacturers require it in their service manuals. Calibration comes in two forms: static, performed in a shop using target boards and controlled lighting, and dynamic, performed by driving the vehicle at specified speeds on roads with clear lane markings. Many newer vehicles need both. Ask the shop before booking whether it handles calibration in-house or subcontracts it. If a driver-assistance warning light appears after the new glass goes in, calibration is needed before the vehicle is driven normally.
Recalls for Defective Glazing
When a manufacturer discovers that glazing fails to comply with FMVSS 205, or NHTSA identifies a safety defect, federal law requires a recall. The manufacturer must notify NHTSA and then contact every registered owner by first-class mail within 60 days of filing its defect report, explaining the defect, evaluating the safety risk, and telling the owner how and when to get it fixed.8eCFR. 49 CFR 577.7 – Time and Manner of Notification
Under 49 U.S.C. § 30120, the manufacturer must remedy the defect at no charge. For a vehicle, the manufacturer can repair it, replace it with a reasonably equivalent vehicle, or refund the purchase price minus a reasonable depreciation allowance. For standalone replacement equipment such as an aftermarket windshield, the manufacturer must repair, replace, or refund. The free-remedy requirement expires if the vehicle was first purchased more than 15 calendar years before the recall notice was issued.9Office of the Law Revision Counsel. 49 USC 30120 – Remedies for Defects and Noncompliance You can check for open recalls on your vehicle by entering the VIN at NHTSA.gov.
Civil Penalties for Violations
Under 49 U.S.C. § 30165, as implemented through the inflation-adjusted regulations at 49 CFR 578.6, a person who violates the motor vehicle safety standards faces a civil penalty of up to $27,874 for each violation. Each individual motor vehicle or piece of equipment counts as a separate violation. For a related series of violations, the maximum penalty can reach $139,356,994.10eCFR. 49 CFR Part 578.6 – Civil Penalties for Violations of Specified Provisions These figures are adjusted periodically for inflation and were most recently updated in December 2024. They apply to manufacturers, distributors, dealers, and repair businesses, and the per-piece structure means a shop installing non-compliant windshields accumulates a separate penalty for every unit.