Windshield and Mirror Requirements for Commercial Vehicles

Windshield Glazing Standards

Under 49 CFR 393.60, every CMV windshield must be made of safety glazing material that meets the requirements of FMVSS No. 205. Safety glazing for windshields is laminated glass that holds together when broken, preventing occupant ejection and maintaining some forward visibility after impact. The windshield must be free of discoloration or damage in the area cleaned by the windshield wipers on the driver's side that impairs the driver's field of view. Any damage in this critical area that is larger than 3/4 inch in diameter can trigger a violation during roadside inspections.

Windshield Damage Criteria

Inspectors evaluate windshield condition based on the location, size, and nature of damage. Cracks, chips, and bull's-eye damage in the swept area of the driver's side wiper are the primary concern. Intersecting cracks, damage that has been improperly repaired, or discoloration from delamination that impairs forward vision are all citable conditions. Damage outside the driver's primary viewing area is evaluated differently but may still be cited if it is severe enough to create a safety hazard. Small chips should be repaired promptly before temperature changes cause them to spread.

Window Glazing and Tinting

All windows in the driver's cab must use safety glazing. Aftermarket tinting on the windshield and front side windows is restricted or prohibited in most states. Federal regulations do not set a specific light transmittance standard, but they require that glazing not impair the driver's ability to see clearly. Many states set minimum visible light transmittance at 70 percent for the windshield and front door windows. Carriers operating across state lines should comply with the most restrictive state standard to avoid citations. Check violation codes related to glazing to understand enforcement criteria.

Mirror Requirements

Every bus and truck must have two rear-vision mirrors, one on each side, firmly mounted and positioned to provide a clear view to the rear along both sides of the vehicle. For vehicles that do not allow rear visibility through the vehicle interior (which includes all tractors pulling trailers), outside mirrors are the only means of rearward visibility. Mirrors must be maintained in a condition that provides a clear, undistorted view. Cracked, broken, loosely mounted, or improperly adjusted mirrors are inspection violations.

Convex and Auxiliary Mirrors

Convex mirrors (also called spot mirrors or fish-eye mirrors) provide a wider field of view and are commonly mounted below or alongside the flat main mirrors. While not all are federally mandated, many states require them, and they are standard equipment on most modern tractors. Hood-mounted convex mirrors help drivers see directly in front of and alongside the cab, reducing blind spots in the right-turn danger zone. Fender mirrors and cross-view mirrors address the area immediately ahead of the bumper where pedestrians and vehicles may be hidden from the driver's view.

Defrosting and Defogging Systems

Under 49 CFR 393.78, every CMV with a windshield must have a functioning windshield defogging and defrosting device. The system must be capable of clearing the windshield during conditions of frost, fog, rain, or snow to maintain adequate forward visibility. This typically means the vehicle's HVAC system must be operational with functioning defrost mode. Inoperative defrosters are a citable violation and can result in an out-of-service order during winter conditions when the driver cannot maintain clear windshield visibility. Test the defroster function as part of the pre-trip inspection.

Windshield Wiper Requirements

Every CMV with a windshield must have at least two windshield wipers, one on the driver's side and one on the passenger's side. Wipers must be powered, in working condition, and capable of effectively clearing rain, snow, and other precipitation. Wiper blades must be in good condition without cracks, tears, or hardening that reduces their effectiveness. Inspect the wiper arms for proper spring tension and alignment. Washer fluid reservoir should be kept filled and the spray nozzles clear. Wiper and washer deficiencies are among the simpler items to correct proactively rather than risk a citation during an inspection.

Camera Monitoring Systems

The trucking industry is increasingly adopting camera monitoring systems (CMS) as supplements or potential replacements for traditional mirrors. FMCSA has explored allowing CMS as alternatives to mirrors on CMVs. Camera systems offer advantages including wider fields of view, digital zoom, low-light enhancement, and recording capability. However, they also introduce reliability concerns related to power supply, weather conditions, and driver distraction. Carriers considering CMS should evaluate their fleet's specific needs and verify regulatory acceptance. Cross-reference vehicle capabilities through VIN data and manufacturer specifications before investing in camera systems.