Whitepaper – How Solar Reflection Location Impacts a Road User

Pager Power’s whitepaper ‘Evaluating the Field of View: Quantifying How the Location of a Solar Reflection Impacts a Road User’ has now been published. The Whitepaper will now be a supporting document to Pager Power’s Glint and Glare Guidance document and informs the methodology when assessing the effects of glint and glare from solar photovoltaic (PV) developments upon road users.

Download the Whitepaper PDF here to read it in full.

Whitepaper Purpose

When determining the impact significance of a visible solar reflection upon a road user and the mitigation requirement, the direction of the reflection panel relative to a road user’s main field of view (FOV) should be determined because any solar reflections that are outside of the road users’ main FOV are considered of less significance than those that are within. However, there is currently a clear lack of guidance and resources pertaining to the effect of glare at different locations relative to a road user, and ultimately evaluating the main FOV. 

The purpose of the white paper was therefore to review relevant guidance and resources from related sectors, such as railway and aviation, to evaluate the specific location of a solar reflection that is considered outside the main FOV so that the impact significance upon a road user can be consistently determined.

Conclusions

The two most relevant resources relating to this topic were the ‘Evaluation of the of Glare as a Hazard for General Aviation Pilots on Final Approach’ report sponsored by the FAA and undertaken by Sandia National Laboratories, and the ‘Signal Sighting Assessment Requirements’ document produced by Network Rail. 

These resources did not conclusively agree as to what should be considered outside the main FOV, with one guidance stating 30 degrees (Network Rail) and the other stating 50 degrees (FAA). Therefore, to determine a nominal value that is consistent with reputable guidance on the topic, professional judgement, evaluation of both literature, and a comparison to the real world application with respect to a road user had to be applied. 

A visual representation of 30 degrees and 50 degrees relative to a road user’s direction of travel are shown in Figure 1 below. Figure 1: 30deg and 50deg relative to a road user’s direction of travel.

Following further consideration, the whitepaper concluded that glare experienced outside of 50 degrees either side of the direction of travel should be considered outside the main FOV and of less significance to a road user. This is based on a conservative approach because there was not sufficient evidence within the current guidance and studies to reduce the location closer to the central axis (0 degrees).

The resulting main FOV that is considered appropriate for a road user is 100 degrees centred on the direction of travel (50 degrees either side of straight ahead).

About Pager Power

Pager Power has undertaken over 750 glint and glare assessments in 51 countries around the world including Europe, India, Australia, and South Africa. For more information about what we do, please get in touch.

References

Thumbnail image accreditation: Kindell Media (Oct, 2021). Last accessed 10 Dec 2021 from Pexels.com. Available at: https://www.pexels.com/photo/industry-technology-usa-reflection-9800003/