Getting driving glasses that tint when sun is bright?

I would recommend Transitions Xtractive Polarised lenses. These will darken and polarise behind the windscreen. However, they will never be as dark as permanently tinted lenses.

If you really want to invest in a fantastic pair of sunglasses, then I would recommend Serengeti drivers but they are expensive in prescription!

Regular transitions dont work behind car windscreens as they filter out the light which the glasses react to. I believe there are some that do specifically work in a car but last time i looked they were insanely expensive. I'd love to have a reactive par of prescription glasses but havent been able to find any affordable ones.

I've had a couple of pairs of expensive transitions over the years. Transition glasses only fully tint when under direct sunlight, when sitting in a car there's some light that's refracted through the windscreen which hit's your lenses but it's not intense light when compared to standing outside, so your transitions will only mildly tint.

You'll get the best results with prescription polarised sunglasses which stay constantly a dark tint. I moved to contact lenses and Oakley polarised sunglasses, also have Decathlon polarised sunglasses and there's a minimal difference if any between them. Both are excellent.

Maybe your car has a sunroof or you bought the more expensive drivewear ones perhaps?

https://www.onlineopticiansuk.com/photochromic-lenses-explained-i149 "Standard photochromic lenses do not work inside a car due to the windscreen blocking out the UV rays which are needed to active the chemical process which causes the lens to darken.

A new lens has been brought to the market that can react inside a car or behind the windscreen without UV rays and uses daylight alone to trigger the reaction. These lenses are known as 'transition drivewear lenses' which combine both photochromic and polarisation technology."