A CAA-Quebec study shows that automobile headlight lenses damaged by harsh weather, abrasives and debris become so opaque that they can reduce lighting effectiveness to half that of headlights in good condition. Tests conducted on a closed track confirm this: a motorist travelling 50 km/h at night will have four more seconds to react to an emergency if the headlights are in good condition and undamaged.

View A CAA-Quebec studyPDF file – 243 KB

A widespread problem

To study the damaged-headlight phenomenon, CAA-Quebec first sent its experts to various public parking lots to look at a representative sample of Quebec’s vehicles. This exercise concluded that 30% of vehicles checked showed obvious signs of headlight opacity, and the problems were very serious in nearly 15% of cases.

Results in a controlled environment …

Using a luxmeter, CAA-Quebec measured illumination (in other words, the quantity of light received by the object being illuminated) before and after the refurbishment of headlight lenses. The results of these tests, conducted in a closed room with no light source, are surprising. They show a difference in illumination of up to 525% lux or 6 times more.

… and on a closed track

Other tests, conducted on a road circuit, also enabled the measurement of the impact of headlight lens opacity on visibility. Black panels of various dimensions were placed at different distances. The results show that the driver of a vehicle with headlights in good condition could see the panels 60 metres sooner than someone driving a vehicle with damaged lenses. The improvement in visibility varied from 92% to 1,200%. For full results of this study, view our video.

“When you are driving at night – especially at this time of year with darkness coming earlier – it is essential to see as far ahead as possible in order to be prepared for any eventuality,” says Sophie Gagnon, CAA-Quebec’s Senior Director, Public and Government Relations. “Considering that more than 90% of the information needed when driving a car comes from visual searching, it is fundamental to have optimal vision, especially at the time of year when many children will be walking on our streets for Halloween.”

The CAA-Quebec tests were conducted when weather conditions were favourable to driver visibility. It could be even more difficult, for example, to notice a pedestrian who is farther away and at the side of the road when it is snowing or raining heavily.

Causes of headlight deterioration

Although headlight opacity is more widespread among vehicles that are more than five years old, CAA-Quebec has observed that it can occur in the earlier years of a vehicle’s life. More than age, the material used to make lenses is at issue. Thus, glass headlights on a vehicle that is more than 10 years old may be found to be in excellent shape, whereas headlights made of polycarbonate are more easily damaged by abrasives and debris such as sand, calcium or salt, as well as by sunlight and rain.

Low-cost corrective measures

To restore headlights to like-new condition, CAA-Quebec recommends dealing with a specialized company that renews lenses completely and sustainably, using a polishing technique. A number of products are sold, but their results are not always long-lasting. “Treatments are available to remedy headlight opacity, and they are not expensive,” Ms. Gagnon says. “There is therefore no excuse for tolerating headlights that fail to illuminate the road sufficiently. All drivers win by having better visibility.”