Driving in sunglasses

What to wear and when

Sunglasses sold for general use can be too dark or unsuitable for driving

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 colour density when exposed to UV light. When the UV source fades, the lenses revert to their previously clear state.

While ideal for general wear, photochromic lenses are not suitable for driving because car windscreens filter out UV light which both slows and limits the reaction of the lenses - you could find yourself driving with lenses too dark or too light as a result.

Several manufacturers produce lenses (which can also be made to your prescription) designed to adapt to the varying light conditions when driving.  Check with your optician.

Tint density

  • 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'.

 

Light transmission Category Use Limitations
 80%-100% (clear)
 Class 0
 indoors/overcast day
 none
 43%-80% (light tint)
 Class 1
 low sunlight
 not for night driving
 18%-43% (mediium tint)
 Class 2
 medium sunlight
 not for night driving
 8%-18% (dark)
 Class 3
 bright sunlight
 not for night driving
 3%-8% (very dark)
 Class 4
 exceptionally bright sunlight
 not for day or night driving

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.

A good quality anti-reflection coating is recommended, along with a hard coating to protect the lenses from scratches.

Sunglasses with deep side arms can block side, or peripheral, vision and are  not recommended for driving.

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 - failing to have your vision corrected and protected from the sun could invalidate your insurance if you are involved in a road traffic accident.

(15 October 2012)