từ google đây cụ
http://www.ehow.com/how_2083903_obey-laws-window-tint.html
cụ có trình độ anh ngữ dịch giùm em chổ này cái:
Step1
Check federal, state and local laws carefully before having window tinting applied to your vehicle. The U.S. Department of Transportation requires a basic 70% visible light transmission (VLT) on windshields and both front windows. This requirement is identified as FMVSS 205 on window tinting law charts and is the typical factory standard on new cars. However, the U.S. government has allowed each state to define their own
window tint regulations which often allow darker shading. Some city governments and police departments also enforce their own local standards.