Motor Vehicles first used before 1 April 1985:
The windscreen and front side windows must allow at least 70% of
light to be transmitted through them.
Motor Vehicles first used on or after 1 April 1985:
The light transmitted through the windscreen must be at least 75%.
The front side windows must allow at least 70% of light to be
transmitted through them.
If the glass is tinted to a point whereby it lets through less light,
then the vehicle does not meet legal requirements.