Truck Windshield, Dash Cam and Mirror Rules
A truck windshield may have a crack that no other crack crosses, and a chip that a 3/4 inch disc covers if it is at least 3 inches from the next one (49 CFR 393.60(c)). Tint on the windshield and the side windows next to the driver must pass at least 70 percent of light. A dash cam or GPS goes within 8.5 inches of the top of the wiper-swept area and out of the driver's sight lines. Trucks need two outside mirrors (49 CFR 393.80).
Facts checked October 17, 2026
Key Points
- A bus, truck and truck tractor must have a windshield, mounted using the full edge of the glass (49 CFR 393.60(b))
- Above the top of the steering wheel, the windshield must be free of damage and discoloration. The 2-inch border at the top and the 1-inch borders at each side are left out (49 CFR 393.60(c))
- Three things are allowed in that area: tint that meets the 70 percent rule, any crack that no other crack crosses, and a damaged spot that a 3/4 inch (19 mm) disc covers if it is at least 3 inches (76 mm) from any similar spot (49 CFR 393.60(c))
- Tint on the windshield and the windows right and left of the driver must let through at least 70 percent of light. The limit does not apply to other windows (49 CFR 393.60(d))
- Dash cams, GPS units, driver camera systems and similar vehicle safety technology may go within 8.5 inches (216 mm) of the top of the wiper-swept area and within 7 inches (175 mm) of the bottom, out of the driver's sight lines to the road and to signs and signals (49 CFR 393.60(e)(1)(ii))
- CVSA decals and required stickers go at the bottom or sides of the windshield, no more than 4.5 inches (115 mm) from the bottom, outside the wiper-swept area (49 CFR 393.60(e)(2))
- A bus, truck or truck tractor needs two outside rear-vision mirrors, one on each side, that meet FMVSS 111 (49 CFR 393.80)
Windshield and mirror limits for commercial motor vehicles
| Item | What the rule says | Where | |
|---|---|---|---|
| Cracks in the checked area | Allowed if no other crack crosses it | 393.60(c)(2) | |
| Chips and damaged spots | Allowed if a 3/4 inch (19 mm) disc covers the spot and it is at least 3 inches (76 mm) from any similar spot | 393.60(c)(3) | |
| Tint on the windshield and the side windows next to the driver | At least 70 percent light transmittance | 393.60(d) | |
| Antennas and similar devices on the inside of the windshield | No more than 6 inches (152 mm) below the top edge, outside the wiper-swept area and the driver's sight lines | 393.60(e)(1)(i) | |
| Vehicle safety technology, such as a dash cam or GPS | No more than 8.5 inches (216 mm) below the top of the wiper-swept area and no more than 7 inches (175 mm) above its bottom edge, outside the driver's sight lines | 393.60(e)(1)(ii) | |
| Inspection decals and required stickers | At the bottom or sides, no more than 4.5 inches (115 mm) up from the bottom, outside the wiper-swept area and the driver's sight lines | 393.60(e)(2) | |
| Outside mirrors | One on each side, firmly attached, meeting FMVSS 111. A truck with an interior mirror view to the rear needs only the driver's-side mirror | 393.80(a) and (b)(2) |
How much damage can a truck windshield have?
Each windshield must be free of discoloration and damage in one area. That area runs upward from the top of the steering wheel. It leaves out a 51 mm (2 inch) border at the top, and a 25 mm (1 inch) border at each side (49 CFR 393.60(c)). Three things are still allowed in that area. One is tint that meets the 70 percent rule. The second is any crack that no other crack crosses. The third is a damaged spot that a 19 mm (3/4 inch) disc can cover, if it is at least 76 mm (3 inches) from any other such spot. Damage below the top of the steering wheel is not part of this test. Glass in windshields, windows and doors must meet FMVSS 205 and carry its marking (49 CFR 393.60(a)).
What window tint is allowed on a truck?
Tint or color on the windshield and on the windows to the immediate right and left of the driver is allowed if the glass passes at least 70 percent of light at normal incidence (49 CFR 393.60(d)). The glass must be marked as having a parallel luminous transmittance of not less than 70 percent. The limit does not apply to other windows on the vehicle. States may have their own tint laws.
Where can you mount a dash cam or GPS?
Federal rules treat these as vehicle safety technology. The definition names driver camera systems, GPS, lane departure warning, forward collision warning, speed management and behavior management systems, and transponders. It covers any device that has cameras, lidar, radar, sensors or video (49 CFR 393.5). Such a device may sit on the inside of the windshield if it is no more than 216 mm (8.5 inches) below the top edge of the area the wipers sweep. It must also be no more than 175 mm (7 inches) above the bottom edge of that area, and outside the driver's sight lines to the road and to highway signs and signals (49 CFR 393.60(e)(1)(ii)). Antennas and similar devices that are not vehicle safety technology must be within 152 mm (6 inches) of the top edge, outside the wiper-swept area and the sight lines (49 CFR 393.60(e)(1)(i)). A device you mount on the dash, not the glass, is outside this section.
Where do inspection decals and stickers go?
CVSA inspection decals, and stickers or decals required by federal or state law, may go at the bottom or sides of the windshield. They may not reach more than 115 mm (4.5 inches) up from the bottom. They must be outside the area the wipers sweep and outside the driver's sight lines to the road and to highway signs and signals (49 CFR 393.60(e)(2)). Other stickers and decals are not covered by that allowance.
What do the rules say about wipers, washers and defrosters?
A bus, truck or truck tractor built on or after December 25, 1968 must have a windshield wiping system that meets FMVSS 104 (S4.1) and a washing system that meets FMVSS 104 (S4.2.2), both as in effect when it was built (49 CFR 393.78(a)). It must also have a windshield defrosting and defogging system that meets FMVSS 103 as in effect when it was built (49 CFR 393.79(a)). Older vehicles have their own rules in the same sections.
What mirrors must a truck have?
Every bus, truck and truck tractor must have two rear-vision mirrors, one on each side, firmly attached to the outside. They must be placed to show the driver the highway to the rear along both sides. They must meet FMVSS 111 as in force when the vehicle was built (49 CFR 393.80(a)). There are three exceptions. A mirror on a vehicle built before January 1, 1981 may stay in service, but a replacement must meet FMVSS 111. A truck built so the driver can see to the rear through an inside mirror needs only the driver's-side outside mirror. A vehicle in a driveaway-towaway operation needs at least one mirror with a clear view to the rear (49 CFR 393.80(b)).
Related Free Tools
Annual DOT Inspection Checklist
Every item from the federal minimum periodic inspection standards as a checklist, with your next due date and what the report must show.
Pre-Trip / Post-Trip DVIR Checklist
A 49 CFR 396.11 compliant Driver Vehicle Inspection Report with defect tracking.
Used Truck Inspection Checklist
What to check before buying a used semi truck: paperwork, engine, frame, tires, and a real test drive.
Frequently Asked Questions
How big a crack can a truck windshield have for a DOT inspection?+
In the checked area, a crack is allowed if no other crack crosses it. A chip or damaged spot is allowed if a 3/4 inch disc covers it and it is at least 3 inches from any similar spot (49 CFR 393.60(c)). The checked area runs up from the top of the steering wheel and leaves out a 2 inch border at the top and a 1 inch border at each side.
Can you mount a dash cam on a semi truck windshield?+
Yes, within limits. It must be no more than 8.5 inches below the top edge of the area the wipers sweep, and no more than 7 inches above the bottom edge of that area. It must also stay out of the driver's sight lines (49 CFR 393.60(e)(1)(ii)).
Where can I mount a GPS on a semi windshield?+
A GPS is vehicle safety technology under 49 CFR 393.5. Use the same limits as a dash cam: within 8.5 inches of the top of the wiper-swept area and within 7 inches of its bottom, outside the driver's sight lines (49 CFR 393.60(e)(1)(ii)).
What are the DOT window tint rules for trucks?+
The windshield and the windows right and left of the driver must pass at least 70 percent of light. The limit does not apply to other windows (49 CFR 393.60(d)). Your state may have its own tint law.
Where do DOT inspection stickers go on the windshield?+
At the bottom or sides, no more than 4.5 inches up from the bottom, outside the wiper-swept area and the driver's sight lines (49 CFR 393.60(e)(2)).
Do antennas and toll transponders have a different mounting rule?+
A transponder is listed as vehicle safety technology, so the 8.5 inch and 7 inch limits apply (49 CFR 393.5 and 393.60(e)(1)(ii)). An antenna or similar device that is not vehicle safety technology must be within 6 inches of the top edge, outside the wiper-swept area and the sight lines (49 CFR 393.60(e)(1)(i)).
How many mirrors does a semi truck need?+
Two outside rear-vision mirrors, one on each side, meeting FMVSS 111. A truck built so the driver can see to the rear through an inside mirror needs only the driver's-side outside mirror (49 CFR 393.80).
Does a truck need a windshield washer and defroster?+
Yes. A truck built on or after December 25, 1968 must have a wiping and washing system that meets FMVSS 104, and a defrosting and defogging system that meets FMVSS 103 (49 CFR 393.78 and 393.79).
More federal trucking rules
- Hours of Service Rules for Truck Drivers
- ELD Mandate: Who Needs an ELD
- DOT Roadside Inspection Levels Explained
- DOT Drug and Alcohol Testing Rules
- Driver Qualification File Requirements
- DVIR and Vehicle Maintenance Rules
- New Entrant Safety Audit Requirements
- Hours of Service Exceptions and Exemptions
- Motor Carrier Insurance Requirements
- CDL Classes, Endorsements and ELDT Training
- DOT Physical and Medical Card Requirements
- Drug and Alcohol Clearinghouse Requirements
- Cargo Securement Rules for Trucks
- Hazmat Basics for Truck Drivers and Carriers
- USDOT Number and Biennial Update Requirements
- Safety Ratings, Compliance Reviews and DataQs
- Federal Truck Size and Weight Limits
- California Clean Truck Check (HD I/M)
- Truth-in-Leasing Rules for Owner-Operators
- Form 2290 Heavy Highway Vehicle Use Tax
- Truck Driver Phone, Texting and Seat Belt Rules
- Railroad Crossing Rules for Truck Drivers
- Truck Emergency Equipment and Warning Triangle Rules
- CDL Disqualification: Major and Serious Offenses
- Truck Tire Rules: Tread Depth, Retreads and Pressure
- Trailer Reflective Tape (Conspicuity) Rules
- Truck Brake Rules: Pushrod Stroke, Lining Thickness and ABS
- Driver Conduct Rules: Alcohol, Drugs, Fatigue, Passengers and Pre-Trip Checks
- English Language Proficiency for Truck Drivers: The 391.11(b)(2) Rule
- Weigh Station Rules: Who Must Stop and What Happens If You Skip
- Truck Lighting Rules: Required Lamps and Reflectors (49 CFR 393)
- Driver Road Test Rules: The Company Road Test and Certificate (49 CFR 391.31)
Related terms and pages
Sources
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This is a plain-language summary for reference, not legal advice. Check the official rule text before you rely on any detail. Ask a compliance professional about your own operation.