The influence of automobile windscreen rake on effective light transmittance

The theoretical transmittances at the installation angle of the windscreens of the ten best-selling cars in the UK in 2008 are investigated. The data show that the ten most popular cars on the UK roads have a windscreen rake that reduces transmittance to a value close to or below that specified in International Standards for normal incidence. British and International Standards for windscreen transmittance should be revisited by the relevant authorities in the light of the high rake angles that have become widespread in recent years. The problem is worsened considerably by tinted windscreens having become the default option in many models. It is also suggested that there may be good reason for all spectacles supplied to drivers for low light level driving to be untinted and anti-reflection coated.