Iowa Requires 70% Light Transmittance on Front Glass

The prohibition itself is in Iowa Code section 321.438(2): a person shall not operate on the highway a motor vehicle equipped with a front windshield, a side window to the immediate right or left of the driver, or a sidewing forward of and to the left or right of the driver which is excessively dark or reflective so that it is difficult for a person outside the motor vehicle to see into the motor vehicle. The statute deliberately carries no percentage. Paragraph (a) instructs the department to adopt rules establishing a minimum measurable standard of transparency which shall apply to violations of this subsection, so the operative figure lives in the Iowa Administrative Code rather than in the Code of Iowa.

That figure is 70 percent light transmittance, set by Iowa Administrative Code rule 761-450.5(321). Anyone searching for the Iowa tint rule by its old number should note that it moved: the Transportation Department rescinded and rewrote chapter 450 through ARC 9133C, published in the Iowa Administrative Bulletin of April 16, 2025 and effective May 21, 2025, and the tint rule that used to sit at 761-450.7 is now 761-450.5. The Department of Transportation still publishes a standalone PDF at the retired 450.7 address containing the superseded text, so check the chapter before relying on a rule number.

The 70 percent standard reaches exactly three pieces of glass: the windshield, the front side window, and the front sidewing. Iowa sets no transmittance figure for rear side windows, for the rear window, or for a sunstrip above the AS-1 line, because section 321.438(2) never mentions them. Those surfaces are governed only by section 321.438(1), which forbids driving a vehicle whose windshield, sidewings, or side or rear windows do not permit clear vision. That is a judgment standard an officer applies by looking, not a meter reading.

Iowa's medical exemption is closed, and closed permanently. Rule 761-450.5(2) preserves only vehicles that were already operating under a dark window exemption issued before July 4, 2012, and it does so by pointing back to rule 761-450.7(3) as that rule stood on April 13, 2022. Under that preserved text the floor is 35 percent rather than 70 percent, the vehicle must still be carrying the passenger or operator named on Form 432020, that form must be signed by a physician licensed under Iowa Code chapter 148, 151 or 154, and Form 432020 must be carried at all times in the vehicle. When the vehicle stops being used to transport that person the exemption expires, cannot be renewed, and the owner has 60 days to bring the glass back to 70 percent. The rule states flatly that effective July 4, 2012, no exemption shall be granted from the minimum standard of transparency.

The only vehicles outside the rule entirely are law enforcement vehicles. Section 321.438(2)(b) disapplies the subsection to a person operating a motor vehicle owned or leased by a federal, state, or local law enforcement agency when the operation is part of the person's official duties.

Tint is checked at the roadside, not in an inspection lane. 476 to stop a motor vehicle or trailer for weighing and inspection to enforce registration, size, weight, and load. 5(1). 8A, subsection 3, paragraph "ai", carrying a fine of $70. Because it is charged by citation in lieu of arrest, the usual route is to pay the scheduled fine or to plead not guilty and contest the meter reading in the district court for the county where the stop occurred. 438.