well depending on the film you choose you can get about 70-85% glare reduction during the daytime. will have to check on night time visibility specs for you. The one above is the black pearl series which is dark and may be a problem with the cops. interior visibility even in the darkest 5% VLT shade is excellent, with very low interior reflectivity. basically you can see out clearly.
The signature series film we install.. (posting some pics shortly), gives a frozen reflective look, available in 60, 45, 35 & 20 VLT (visible light transmission) it doesn't look black so the cops don't spot it as such.. probably think its a really clean windscreen. we've used it on many a windscreens and no complaints and no one has ever had one taken off. i have it installed on my car as well, night time glare from incoming headlights is greatly reduced but can still be annoying. the car looks very cool though 
hope this helps
