A recent column about vehicle equipment standards prompted a message form reader R.C., who commented, “I am sure I could find the state code site (for Idaho, since I’m in Idaho) but an article covering the subject might be appropriate since it’s quite involved.  I understand each vehicle window has specific requirements and police apparently can check those limits with a device to ensure compliance.  It would be interesting to read the details of such in both Washington and Idaho.”

Application of sun screening material to motor vehicle windows has become 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 can be applied in the aftermarket by independent shops and consumers.

Many readers have expressed annoyance over not being able to see vehicle occupants from the outside due to super-dark or reflective window glazing.  Others have been startled at first when making a traffic check through an SUV’s factory-tinted rear quarter glass; lights can be seen, but unlit objects are fairly 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 several decades, the prominence of darkened glass from top-to-bottom elsewhere is a more recent phenomenon, especially on rear SUV windows.  As a result, federal and state standards of compliance are necessary 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.  Regarding 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.

As R.C. mentioned, 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 certain individuals.  Idaho law exempts, for example, “A motor vehicle operated by, or carrying as a passenger, a person who possesses written verification from a licensed physician that the operator or passenger must be protected from exposure to sunlight or heat for medical reasons associated with past or current treatment; such written verification shall be carried in the vehicle.”

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 email at precisiondriving@spokesman.com.

---

---