Missouri Window Tint: 35% on the Front Side Windows, Nothing on the Windshield

The operative number sits in the first sentence of Section 307.173.1: a sun-screening device on a front sidewing vent or on the window immediately to the left or right of the driver must have a light transmission of thirty-five percent or more, plus or minus three percent, in conjunction with the safety glazing material underneath it. Because the statute measures the film and the factory glass together, the figure that counts is the net reading through the assembled window, not the number printed on the film's box. A second, separate figure applies at the same time: luminous reflectance must be thirty-five percent or less, plus or minus three percent, which is what rules out the mirrored and chrome-look films that would otherwise pass a light-transmission test.

What the section leaves out matters as much as what it says. Section 307.173 addresses only the front sidewing vents, the windows immediately left and right of the driver, and the windshield. Rear side windows and rear glass appear nowhere in it, so Missouri imposes no percentage on them and attaches no outside-mirror condition to dark rear tint. The windshield rule runs the other way and is absolute: except as allowed by subsection 2, all sun-screening devices applied to the windshield are prohibited. Subsection 2 preserves factory-installed tinted glass and its equivalent replacement, and it preserves tinting material applied to the upper portion of the windshield that is normally tinted by the manufacturer of motor vehicle safety glass. Missouri does not describe that band as an AS-1 line and does not give it in inches, so the lawful strip is defined by what the glass manufacturer itself tints. Subsection 2 also protects labels, stickers, decalcomania and informational signs, and it permits tinted or solar screening material on recreational vehicles as defined in Section 700.010, provided the material does not interfere with the driver's normal view of the road.

The medical route is a real permit, not a doctor's note carried in the glovebox. The Department of Public Safety may issue a permit to a person with a serious medical condition whose physician prescribes a sun-screening device, and Section 307.173.1 lets that permit cover any titleholder or a relative within the second degree by consanguinity or affinity who lives in the household, a list the statute spells out as spouse, grandparent, parent, brother, sister, niece, nephew, aunt, uncle, child and grandchild. The procedure is in 11 CSR 30-7.010: the prescription must have been issued within one year of the application, and the applicant presents both the prescription and the vehicle to the Missouri State Highway Patrol's Motor Vehicle Inspection Division. One prescription can cover several vehicles, but every vehicle must be brought in. A certifying officer or motor vehicle inspector verifies the prescription for authenticity, completes form SHP-524 in triplicate, affixes the sticker to the inside of the windshield on the lower left side slightly above where the inspection sticker goes, and places the decal on the outside lower left corner of the rear glass or the left corner of the rear bumper at the owner's option. The driver keeps a copy of the form in the vehicle at all times. The permit stays valid during the current ownership of that vehicle only, so it does not survive a sale. Permits issued before August 28, 2001 that allowed windshield tinting on a physician's prescription are expressly preserved by the same rule.

One more class of vehicle sits outside the whole section: Section 307.173.5 exempts any vehicle licensed with a historical license plate, the registration created by Section 301.131.

Enforcement is almost entirely roadside, which surprises Missourians who assume the safety inspection catches tint. Missouri does still run a biennial inspection under Section 307.350, but only for vehicles that have passed the ten-year period following their model year or exceeded one hundred fifty thousand miles, with even model years inspected in even calendar years and odd model years in odd. Glazing is one of the listed inspection items under Section 307.360, yet the Highway Patrol's glazing rule, 11 CSR 50-2.270, contains no light-transmittance figure anywhere in it. Its only tint-related rejection is subsection (5)(C), aftermarket vision reducing material or other conditions that obscure the driver's vision on the windshield. The thirty-five percent side-window standard is therefore never metered in a Missouri inspection lane; it is measured by an officer at the roadside.

1(4) a fine of up to seven hundred fifty dollars. That is unusual within Missouri's equipment chapter, where most offenses, including the auxiliary lamp and cowl lamp rules, are only infractions capped at four hundred dollars. A tint stop therefore produces a criminal charge rather than a ticket that can be disposed of as a non-criminal violation. 385 lets the superintendent of the Missouri State Highway Patrol notify the director of revenue in writing, after which the director shall suspend the registration of a vehicle that is not equipped as required by law. 355 makes a current certificate a precondition of registration or transfer.