Driving in Sunglasses
What to wear and when
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 has to get to your eyes.
A visit to an optician for an eye examination will ensure that your vision is as good as it should be, and will tell you whether you need corrective lenses as well as helping you get the right sort of sunglasses.
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
As the name suggests, these remain the same darkness density regardless of the prevailing light conditions. Fixed tint sunglasses are readily available and a fixed tint can be added to prescription, or corrective, glasses too.
Graduated lenses are darker towards the top of the lens. Both options are available in a broad choice of colours.
Polarised lenses are normally fixed tints, but their inherent properties can significantly help to reduce glare. Their effect can be very evident on wet roads.
Variable Tint lenses
These are generally known as 'photochromic' lenses and have the advantage of changing their colour density when exposed to UV light (UV causes a change in the lens's chemical structure). When the UV source fades, the lenses revert to their previously clear state.
While these lenses are ideal for general wear, they are not suitable for driving because car windscreens filter out UV light and therefore slow down and limit the reaction of the photochromic lenses. You could find yourself driving with lenses too dark or too light for the prevailing conditions.
To overcome these problems several manufacturers have produced lenses - which can also be made to your prescription - which adapt to the varying light conditions when driving. Your optician will guide you to the best option for your needs.
Tint density
Tinted lenses are graded according to the density of the tint. Refer to the table below or ask your optician for advice. All sunglasses should, by law, be labelled and show the filter category number.
| Light transmission | Category | Use | Limitations |
| 80% to 100% | Class 0 (clear or lightly tinted lenses) |
Indoors/overcast day | None |
| 43% to 80% | Class 1 (lightly tinted lenses) |
Low sunlight | Not suitable for night driving |
| 18% to 43% | Class 2 (medium tinted lenses) |
Medium sunlight | Not suitable for night driving |
| 8% to 18% | Class 3 (dark lenses) |
Bright sunlight | Not suitable for night driving |
| 3% to 8% | Class 4 (very dark lenses) |
Exceptionally bright sunlight | Not suitable for day or night driving |
Lenses with light transmission less than 75% are unsuitable for night driving.
Yellow tinted lenses are not recommended for night driving. If the lens has a light transmission factor of 75% or more to meet night driving requirements then the tint is likely to be unperceivable anyway.
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'.
Graduated Lenses
Some drivers like the benefits of a graduated tint, as the top part of the lens in which you look out is darkest. The bottom part of the lens is generally lighter and this makes it easier to see the controls within the car.
Safety of the Lenses
All sunglasses should carry the CE mark and meet the European Standard BS EN 1836:2005. They must be able to withstand a load of 100 Newtons applied by a 22mm steel ball for around ten seconds.
A good quality anti-reflection coating is recommended, along with a hard coating to protect the lenses from scratches.
Sunglasses with deep side arms should not be worn for driving as this can block side, or peripheral, vision.
Summary
- Have a thorough eye examination every two years to find out if you need prescription lenses within your sunglasses
- Discuss the options for sun and glare protection with your optician
- Consider a specialist driving lens or tint
- Be aware that your every day sunglasses might not be suitable for driving
- Always keep a spare pair of driving sunglasses in the car
- Remember, the onus is on you to have good vision and failing to have your vision corrected and protected from the sun could invalidate your insurance if you are involved in a road traffic accident.
3 June 2010