On the road: headlight glare study published

New research into headlight glare has provided a series of considerations for the Department for Transport (DfT).

Independent research consultancy, Transport Research Laboratory (TRL), launched a project last year to explore the issue of headlight glare through a survey of drivers and an on-road data collection study.

The survey of 1850 UK drivers found that drivers “perceive glare from vehicle headlamps to be an important and widespread issue when driving at night.”

More than half of drivers surveyed reported having stopped or reduced driving at night, or said they would if they could, due to headlamp glare.

Headlamps with more of a white hue were generally perceived to be particularly problematic for causing glare.

TLR used an instrumented left-hand drive car to collect luminance data from the usual driver eye position. This was driven on routes through several types of roads and locations, with sensors to measure luminance and characteristics of the driving environment – such as the pitch and roll of the car and other vehicles.

An observer present in the car also recorded subjective observations by pressing a button when they experienced glare that they felt might interfere with their driving. Machine learning analysis was then used to look for patterns in the data.

Analysis from the on-road data collection project indicated that higher levels of luminance (brightness) were associated with an increased likelihood of glare being experienced by the on-board observer, with researchers noting: “This suggests that brighter headlamps are more likely to cause glare.”

The pitch and roll of the test vehicle and locations were also found to influence the likelihood of glare being experienced by the observer. This included driving uphill, or around bends in the road.

The researchers found that vehicle type was important in influencing glare – but noted that future research should seek to expand on this area.

The research aimed to provide information that the DfT could use to reduce the likelihood of drivers experiencing glare on UK roads.

The TLR set out five considerations for the DfT based on the findings of its research.

The first consideration was to improve the understanding of road users’ experience of glare, such as through annual surveys from representative samples. Running public information campaigns on the situations in which drivers might be more likely to experience, or cause, glare was also put forward.

Further research into vehicle design parameters resulting in glare was identified as a further consideration. Researchers suggested that the project provided some data suggesting LED lighting and vehicle height might be important factors, but noted that further research is needed to confirm this.

The final considerations encouraged improving lighting regulations to reduce glare, and to conduct additional research to support further understanding of glare in driving.

TRL researchers noted that manufacturers currently test against luminous intensity – how much light is coming out of a headlamp in a particular direction – suggesting instead that the measurements taken should be how bright the light appears to the observer.

Rod Dennis, senior policy officer for the RAC, commented on the publication of the report: “Having campaigned hard for this study, we welcome its findings which independently confirm what drivers have been telling us – that rather than being an imagined phenomenon, some bright headlights do cause a glare problem.”

Dennis identified a need for “balance” between high-performing headlights and reducing the effects of dazzle.

He said: “We don’t yet have all the answers, but this report undoubtedly helps move us towards tackling the complex problem of glare from vehicle headlights. It’s vital the report and its considerations are now reviewed carefully to put us on a path towards changes that ultimately benefit all road users.”

The RAC has completed its own research into the opinions of drivers on headlight glare, finding that 82% of drivers are concerned about being dazzled by vehicle headlights as the evenings get darker.

Adam Sampson, chief executive of the AOP, welcomed the report, sharing: “We know that many drivers worry about the effects of being dazzled by headlights, and are deeply concerned about the impact of new LED lights on their driving experience and want to see change in this area.”

“This report helps to further the understanding of how glare and how our vision interact – identifying the factors that worsen symptoms and those people who are particularly affected,” he said.

Sampson continued: “As advocates on vision and driving in the UK, we believe the Government and DfT should be taking every step to ensure they are keeping pace with the technological changes in modern headlights and providing evidence-based regulatory updates, where needed, to maintain safety for all road users.”