Timpanaro, A., Moody, C., Richardson, W., Reckamp, B. et al., "Quantification of Headlamp Degradation Due to Exposure to the Elements," SAE Technical Paper 2016-01-1471, 2016, doi:10.4271/2016-01-1471.
It is well known that older vehicles’ headlight assemblies degrade with exposure to the elements and can become cloudy or crazed. It is also known that the degradation decreases the amount of useful light projected forward, which can drastically reduce night time or down-road visibility. Testing has been performed to measure the available light projected by old degraded headlamp assemblies and new replacement assemblies, to quantify the decrease in emitted light caused by the degradation. The work has been extended to quantify the improvement in available light when the degraded lenses are treated with commercially available restoration products. Five different vehicle headlamp assemblies representing four different manufacturers were tested measuring the illumination at a given distance with a modified Extech® illuminance meter. The illuminance was mapped at various points spanning plus or minus 24 degrees horizontally and plus or minus 4 degrees vertically to examine the effect of degradation in the overall lighting pattern as well as the intensity. This paper compares illuminance measurements from three types of vehicle headlight assemblies from each model vehicle: new replacement assembly, old degraded assembly, and old assembly with professionally restored lens.