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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883


Too dark for comfort

Application of sun screening material to motor vehicle windows is a large business.  The popularity of the concept has many vehicles coming directly from the manufacturer with this option chosen for the side and rear glass.  Also, leaving open the potential for non-compliance, tinting is applied in the aftermarket by independent shops and consumers.

Some readers have expressed annoyance over not being able to see vehicle occupants from the outside due to too-dark or reflective window glazing.  Others have been startled when making a traffic check through an SUV’s factory-tinted rear quarter glass when lights can be seen, but unlit objects are nearly invisible.  Further, police risk their lives even more than usual when approaching a vehicle with a too-dark driver window.

While a shaded strip at the top of a windshield has been a consumer choice for decades, the prominence of darkened glass everywhere is a more recent phenomenon, especially on SUV rear side windows.  As a result, federal and state standards of compliance attempt to keep privacy glass from becoming too private.

The general federal standard is that all vehicle glass should transmit 70 percent of available light.  Factory glass that is considered “untinted” is generally of the “70 percent transmission” variety.  Though states’ rules vary and allow further tinting on selective windows, the federal rules have a major loophole too.

The fed’s rules for trucks (including SUVs) are less stringent.  While still specifying 70 percent glass for windshield and front windows, rear and back glass can be tinted to any darkness as long as the vehicle has two side mirrors.  Most factory tints on the back and rear SUV windows are fairly dark, transmitting about 20 percent of visible light.

In Washington, you may legally tint your front door SUV windows to 24 percent VLT (visible light transmission); the back half can be any darkness you desire.  For passenger vehicles, you may tint up to 24 percent on all windows except the windshield. Any windshield tinting may not extend beyond a maximum of a 6-inch band from the top, or the “AS-1” mark (a windshield marking designating permissible shading region). 

Mirror-finish products, along with red, yellow, gold or black materials are prohibited in Washington.  Total reflectance may not exceed 35 percent at any window position.

Idaho law also disallows the use of reflective materials on vehicle glass and forbids tinting below a 6-inch line from the windshield’s top, or the specified AS-1 mark.

Whereas Washington allows 24 percent VLT, Idaho requires the VLT reading to be 35 percent for front side glass and vent windows.  So, a vehicle which is legal in Washington may be out of compliance in Idaho.

Though more stringent about dark tint on front side glass, Idaho allows darker tint than Washington on passenger car rear side windows, specifying 20 percent VLT tint on windows in those positions.  For all requirements, Idaho offers a tolerance variation of plus-or-minus 3 percent.

Traffic enforcement officers carry a device that can measure light transmission and reflectance, so determining compliance is an exact science.

Both states have exemptions from these guidelines for individuals who must be protected from sunlight or heat exposure for medical reasons per written verification from a physician.

If you have a used vehicle with tint of unknown origin, you should verify compliance with the laws in your state.

Readers may contact Bill Love via e-mail at