One of the most complained-about factors on the roads in Great Britain is glare from vehicle headlamps. Numerous public surveys and data from membership organisations point to this being perceived as a growing problem, with drivers often reporting that specific types of headlamps (LEDs) and specific models of vehicle are to blame, and that headlamps in general are getting brighter.

Although glare from headlamps is not often identified in collision statistics, it is plausibly a factor in collisions in which drivers were unaware that their vision was affected (so-called 'disability' glare is not always recognised by drivers). Glare can also cause drivers to avoid driving because of the unpleasant sensation, even in the absence of a performance deficit (so-called 'discomfort' glare).

This project, funded by the Department for Transport, used an instrumented vehicle to gather data on luminance, ambient lighting conditions, vehicle inclination, and subjective ratings of glare from driving in dusk and dark conditions on various types of roads and in varying traffic conditions. The measurements were analysed to understand those factors associated with levels of luminance likely to be associated with high levels of perceived glare in oncoming drivers. The findings will be used to inform lighting regulations, and advice to drivers on how to avoid high risk glare situations.

Dr Shaun Helman, Chief Scientist, TRL