Measurement of the reflection properties of road surfaces to improve the safety and sustainability of road lighting

This study reports on a New Zealand-wide evaluation of road surfaces for reflection properties relevant to road lighting design. The sections of road to be surveyed were chosen from the national Road Assessment and Maintenance Management database (RAMM) on the basis of location, age and surfacing material. The measurement device was the portable reflectometer known as ‘Memphis’. Road lighting for safety in New Zealand is currently based on the Australian and New Zealand standards AS/NZS 1158.1.1:2005 and AS/NZS 1158.2:2005, and use modified CIE tables of pavement reflectance based on New Zealand measurements made in 1982. The study measured 140 sites, from Auckland to Christchurch, over a 6-week period from October to December 2008. It found an average luminance co-efficient of 0.050 and an average specular factor of 0.57, which are significantly different to the values being used in design today. The low average luminance co-efficient value (44 per cent below the current design value) means that New Zealand lighting designs will be darker than expected and often produce high levels of glare. If adopted in full, the new design figures are likely to increase the capital and operating costs of new traffic route lighting by around 50 per cent. This figure may reduce in time as luminaire optics better align with the new road surface design figures. (a)