The issue of window tint seems to come up almost daily in the RV Transport industry. As is to be expected, the Federal Motor Carrier Safety Regulation governing this is pretty clear, but not the easiest to understand.
The Regulation Says...
The regulation that governs window tint is "§ 393.60: Glazing in specified openings." Specifically, § 393.60 (d) states:
Coloring or tinting of windshields and windows. Coloring or tinting of windshields and the windows to the immediate right and left of the driver is allowed, provided the parallel luminous transmittance through the colored or tinted glazing is not less than 70 percent of the light at normal incidence in those portions of the windshield or windows which are marked as having a parallel luminous transmittance of not less than 70 percent. The transmittance restriction does not apply to other windows on the commercial motor vehicle.
The guidance from the FMCSA on this section confirms that, indeed, windows may be tinted:
Question 1: May windshields and side windows be tinted?
Guidance: Yes, as long as the light transmission is not restricted to less than 70 percent of normal (refer to the American Standards Association publication Z26.1-1966 and Z26.1a-1969).
However, this is VERY misleading.
The Regulation Means...
Notice that the regulation never addresses what level of tint can be added to the front side windows and the windshield. The regulation never addresses how dark the tint can be, only that 70% of light must pass through the window when measuring "parallel luminous transmittance."
What is Parallel Luminous Transmittance?
Luminous Transmittance is simply a measurement of how much of the light on one side of the glass makes it to the other side. If a window were made of perfectly clear glass (which, by the way, does not exist.....any glass blocks some of the light), then the VLT would measure 100%.
If we measure standard, untinted safety glass, the results are somewhat surprising. Standard safety glass (usually tempered glass on the side windows, laminated safety glass on the windshield) blocks 20% to 25% of the glass with no additional tint whatsoever.
Adding even a small amount of tint will almost always push the VLT below the federal legal limits.
Even if the tint is barely noticeable, the violation becomes even more severe.
How is VLT measured?
Visible light transparency can be measured in a number of ways, but the most popular choice (by both Synergy RV Transport and by law enforcement) is by a tint meter. The tint meter simply provides light on one side of the glass and measures how much of the light goes through the window.
For law enforcement it is an easy read. They place this on the window, and if it reads less than 70 (as it will with any tinted glass), they write the ticket.
But it is legal in my state!
Like most regulations involving passenger vehicles, tint laws can vary wildly by state. Some states mandate 70% or greater VLT, while some states allow almost black tint to be passed through. Some states even govern the color of the tint that can be used.
How can this affect me?If the commercial motor vehicle you are driving has tint that reduces the VLT of the windshield or the front side windows, to below 70%, you can be cited. This citation comes with CSA points that are on your record for three years as well as a fine of up to in excess of $400. Moreover, since law enforcement personnel have a well-earned reputation for disliking window tint, you increase your chances of getting a closer look from an inspector. Finally, if your visibility is called into question in an accident investigation, the accident could be considered more your fault.
Sources: FMCSR Part 393.60 (Regulation and Guidance)
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