<pre> 547.613. RESTRICTIONS ON WINDOWS. (a) Except as
provided by Subsection (b), a person commits an offense that is a
misdemeanor:
(1) if the person operates a motor vehicle that has an
object or material that is placed on or attached to the windshield
or side or rear window and that obstructs or reduces the operator's
clear view; or
(2) if a person, including an installer or
manufacturer, places on or attaches to the windshield or side or
rear window of a motor vehicle a transparent material that alters
the color or reduces the light transmission.
(b) This section does not apply to:
(1) a windshield that has a sunscreening device that:
(A) in combination with the windshield has a
light transmission of 25 percent or more;
(B) in combination with the windshield has a
luminous reflectance of 25 percent or less;
(C) is not red, blue, or amber; and
(D) does not extend downward beyond the AS-1 line
or more than five inches from the top of the windshield, whichever
is closer to the top of the windshield;
(2) a wing vent or a window other than a windshield if
the vent or window has a sunscreening device that in combination
with the vent or window has:
(A) a light transmission of 25 percent or more;
and
(B) a luminous reflectance of 25 percent or less;
(3) a rear window, if the motor vehicle is equipped
with an outside mirror on each side of the vehicle that reflects to
the vehicle operator a view of the highway for a distance of at
least 200 feet from the rear;
(4) a rearview mirror;
(5) an adjustable nontransparent sun visor that is
mounted in front of a side window and not attached to the glass;
(6) a direction, destination, or termination sign on a
passenger common carrier motor vehicle, if the sign does not
interfere with the vehicle operator's view of approaching traffic;
(7) a rear window wiper motor;
(8) a rear trunk lid handle or hinge;
(9) a luggage rack attached to the rear trunk;
(10) a side window that is to the rear of the vehicle
operator on a multipurpose vehicle;
(11) a window that has a United States, state, or local
certificate placed on or attached to it as required by law;
(12) a motor vehicle that is not registered in this
state;
(13) a window that complies with federal standards for
window materials, including a factory-tinted or a pretinted window
installed by the vehicle manufacturer, or a replacement window
meeting the specifications required by the vehicle manufacturer;
(14) a vehicle that is:
(A) used regularly to transport passengers for a
fee; and
(B) authorized to operate under license or permit
by a local authority; or
(15) a vehicle that is maintained by a law enforcement
agency and used for law enforcement purposes.
(c) A manufacturer shall certify to the department that the
sunscreening device made or assembled by the manufacturer complies
with the light transmission and luminous reflectance
specifications established by Subsection (b) for sunscreening
devices in combination with a window.
(d) The department may determine that a window that has a
sunscreening device is exempt under Subsection (b)(2) if the light
transmission or luminous reflectance varies by no more than three
percent from the standard established in that subsection.
(e) It is a defense to prosecution under this section that
the defendant or a passenger in the vehicle at the time of the
violation is required for a medical reason to be shielded from
direct rays of the sun.
(f) It is not an offense under this section for a person to
offer for sale or sell a motor vehicle with a windshield or window
that does not comply with this section.
(g) In this section:
(1) "Installer" means a person who fabricates,
laminates, or tempers a safety glazing material to incorporate,
during the installation process, the capacity to reflect light or
reduce light transmission.
(2) "Manufacturer" means a person who:
(A) manufactures or assembles a sunscreening
device; or
(B) fabricates, laminates, or tempers safety
glazing material to incorporate, during the manufacturing process,
the capacity to reflect light or reduce light transmission.
Acts 1995, 74th Leg., ch. 165, 1, eff. Sept. 1, 1995. Amended
by Acts 1997, 75th Leg., ch. 165, 30.118(a), eff. Sept. 1,
1997; Acts 2003, 78th Leg., ch. 136, 1, eff. Sept. 1, 2003.</pre>
http://www.capitol.state.tx.us/statutes/docs/TN/content/htm/tn.007.00.000547.00.htm#547.613.00
It's not too clear since about the rest of the windows (rear passengers and rear glass) since it's all "legalese", but it does reiterate the fact that 30%, or technically 25%, is the lowest for the front.
