49 CFR 393.60 is the federal regulation that governs windshields and windows on commercial motor vehicles operating in interstate commerce. It sets four things a driver or carrier needs to get right: the glazing material and its markings, what damage and tint are allowed in the driver’s viewing area, where devices and required decals can be mounted, and how the windshield itself is installed. Getting any of these wrong can put a truck out of service at the roadside.
The Critical Viewing Area
Almost every restriction in 393.60 keys off a specific zone on the windshield. Find that zone first and the rest of the rule makes sense.
The critical viewing area starts at the height of the top of the steering wheel and runs upward. It excludes a 2-inch (51 mm) strip along the top of the windshield and a 1-inch (25 mm) strip along each side.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings Inside those borders, from steering wheel height up, the damage and tint limits are strict. Outside them, they are not.
What Windshield Damage Is Allowed
Within the critical viewing area, the windshield must be free of discoloration and damage. Three exceptions are written into the rule, and they are exceptions, not rules of thumb.
- A single crack of any length, as long as it does not intersect another crack.
- Discoloration that is not in the driver’s direct line of sight to the road, highway signs, or signals.
- A damaged spot that fits within a 3/4-inch (19 mm) disc, provided it sits at least 3 inches (76 mm) from any other similar damaged area.
Anything that doesn’t fit one of those three descriptions is a violation.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings Two cracks that cross each other fail, no matter how short. A cluster of small chips less than 3 inches apart fails, even if each chip on its own would pass. A single long crack running most of the way across the windshield technically passes, as long as no second crack intersects it. Drivers regularly assume any visible crack is a citation; the federal rule is narrower than that.
Outside the critical viewing area, 393.60 does not impose the same size and spacing limits.2eCFR. 49 CFR 393.60 – Glazing in Specified Openings Damage in the bottom portion below steering wheel height, or in the 2-inch and 1-inch border strips, is not measured the same way. Severe damage anywhere on the windshield can still be cited if it compromises the glass or interferes with vision in a way an inspector considers unsafe.
Tinting and Coloring
The windshield and the windows immediately to the left and right of the driver may be tinted, but the parallel luminous transmittance through the glazing must be at least 70 percent of light at normal incidence. The 70 percent floor applies to both factory-installed coloring and aftermarket film.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings
A factory shade band along the top edge is permitted, because it sits inside the 2-inch top border that is excluded from the critical viewing area. Many aftermarket films sold for passenger cars do not meet 70 percent transmission. Before installing anything on a commercial vehicle, get documentation from the installer showing the film’s light transmittance rating.
Devices Mounted on the Windshield
Section 393.60(e) controls where GPS units, ELDs, dashcams, transponders, and sensors can sit on the glass. The rule treats “vehicle safety technology” more generously than everything else.
Antennas and Other Non-Safety Devices
Antennas and similar devices must sit no more than 6 inches (152 mm) below the upper edge of the windshield, entirely outside the wiper-swept area, and outside the driver’s sight lines to the road, highway signs, and signals.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings In practice, that puts them in the upper corner where the wipers don’t reach.
Vehicle Safety Technology
A wider mounting window is available for equipment that qualifies as vehicle safety technology under 49 CFR 393.5. The definition covers lane departure warning, forward collision warning, driver camera systems, GPS, transponders, active cruise control, speed management, attention assist, traffic sign recognition, and systems using cameras, lidar, radar, or sensors.3eCFR. 49 CFR 393.5 – Definitions
These devices may be mounted inside the wiper-swept area, but within measured limits:
- No more than 8.5 inches (216 mm) below the upper edge of the wiper-swept area.
- No more than 7 inches (175 mm) above the lower edge of the wiper-swept area.
- Outside the driver’s sight lines to the road, highway signs, and signals.
Those measurements come from a 2022 FMCSA rulemaking that replaced the earlier exemption process for windshield-mounted safety technology.4Federal Register. Parts and Accessories Necessary for Safe Operation; Authorized Windshield Area for the Installation of Vehicle Safety Technology Even inside the allowable zone, a device that blocks the driver’s view of mirrors, signals, or signs will draw a violation.
Required Decals and Other Stickers
CVSA inspection decals and stickers required by federal or state law can go on the windshield, but only along the bottom or sides. They cannot extend more than 4.5 inches (115 mm) from the bottom edge, must sit outside the wiper-swept area, and must stay clear of the driver’s sight lines to the road, signs, and signals.2eCFR. 49 CFR 393.60 – Glazing in Specified Openings
Non-required stickers, company logos, and decorative decals are not authorized on the windshield under the federal rule. Toll transponders follow the same mounting restrictions as other windshield-mounted devices.
Glazing Material and Marking
All glazing used in windshields, windows, and doors on vehicles manufactured on or after December 25, 1968, must meet Federal Motor Vehicle Safety Standard No. 205 as it was in effect on the vehicle’s build date, and the glass must be permanently marked to that standard.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings FMVSS 205 incorporates ANSI Z26.1, the American National Standard for Safety Glazing Materials.5Federal Register. Federal Motor Vehicle Safety Standards; Glazing Materials
The mark you’ll see in the corner of a compliant windshield is usually “AS-1,” the designation for glazing that meets the highest light transmission and impact resistance category for windshield use. Missing or illegible markings are a violation on their own, separate from any damage or tint issue.
Every bus, truck, and truck-tractor must be equipped with a windshield, and each windshield or panel of a multi-piece windshield must be mounted using the full periphery of the glazing.1eCFR. 49 CFR 393.60 – Glazing in Specified Openings Gaps around the edge of an improperly installed windshield fail the rule even if the glass itself is fine.
What a Violation Costs You
Each violation under 393.60 carries a severity weight of 1 in FMCSA’s Compliance, Safety, Accountability system and falls within the Vehicle Maintenance BASIC. The individual violation codes cover missing windshields, damaged or discolored windshields, tinting below 70 percent transmittance, and obstructed windshields.6Federal Motor Carrier Safety Administration. SMS Methodology Appendix A – Violations List
A severity weight of 1 is the lowest on the CSA scale. Violations still accumulate over a two-year window, and carriers with high Vehicle Maintenance scores can be flagged for warning letters and compliance reviews. The more immediate risk is at the roadside: an inspector can place the vehicle out of service until the windshield is repaired or replaced, which means the truck sits until a mobile glass technician arrives or a tow is arranged. A full windshield replacement on a Class 8 truck typically runs between $400 and $1,500 for parts and labor, but the missed delivery window, detention fees, and idle driver time usually cost more than the glass.
A thorough pre-trip inspection catches most 393.60 problems before they become citations. A chip that fits inside a 3/4-inch disc today can spread into an intersecting crack overnight, and once it does, the vehicle is no longer compliant.