Driving in sunglasses
What to wear and when: Sunglasses sold for general use can be too dark or unsuitable for driving
Blinding glare caused by a low sun, or by bright light reflecting off snow, puddles, the car in front, or even your own bonnet can be potentially lethal, particularly when driving at speed.
Glare is frequently cited as the cause of road traffic accidents, but the right pair of sunglasses can prevent it.
There is some confusion though about what sort of sunglasses you should wear when driving, so the AA has sought the advice of The Federation of Manufacturing Opticians, for guidance.
Clarity Of Vision
There are two essential requirements for lenses to be used for driving – vision must remain clear, and sufficient light to let you see properly must get to your eyes.
Sunglasses sold for general use can be too dark or unsuitable for driving.
Sun lenses for driving fall into two main categories – ‘fixed’ and ‘variable’ tint.
Fixed Tint Lenses
These remain the same darkness regardless of light conditions. Fixed tint sunglasses are readily available and a fixed tint can be added to prescription, or corrective, glasses too.
Polarised lenses normally have a fixed tint, but their inherent properties can significantly help to reduce glare. Their effect can be very evident on wet roads.
Variable Tint Lenses
Generally known as ‘photochromic’ lenses, these have the advantage of changing their tint density when exposed to certain kinds of light.
Lenses that only react to UV light are not suitable for driving because car windscreens filter out UV, slowing and limiting the reaction of the lenses – you could find yourself driving with lenses too light as a result.
For driving you need to look for lenses designed to react to visible light as well as to UV to ensure that they will adapt to the varying light conditions when driving. Check with your optician.
- Tinted lenses are graded according to the density of the tint, and all sunglasses should, by law, be labelled and show the filter category number.
- Lenses with light transmission less than 75% are unsuitable for night driving.
- Yellow tinted lenses are not recommended for night driving. The tint is likely to be unperceivable anyway if the lens has a light transmission factor of 75% or more to meet night driving requirements.
- Lenses with light transmission less than 8% are unsuitable for day or night driving.
- Due to the light levels within the car, filter category 2 lenses which transmit between 18% and 43% of light are recommended for daytime driving.
- Filter category 4 lenses only transmit between 3% and 8% of light and are not suitable for driving at any time. Sunglasses with these lenses should, by law, be labelled ‘Not suitable for driving and road use’.