Light emitting diodes (LEDs) are the latest innovation in road lighting technology and are brightening the nation with the help of the Transport Agency.
The transition to LED road lighting from sodium lighting and other sources throughout New Zealand has been slowly implemented over the last 10 years.
The benefits of LED lights include:
LED road lighting is proving to be the lowest whole of life cost lighting option in almost all situations – for new and renewal of existing installations.
The LED lights we most often use are 4000K* (a neutral white light) as current research into light and road safety indicates this is the best and safest colour temperature for object recognition for drivers and pedestrians.
The specifications for road lighting in New Zealand are outlined in the M30 Specification and guidelines for road lighting design.
The Transport Agency therefore expects LEDs will be an included option in all future road lighting investment proposals. In the Transport Agency’s economic evaluation terms, LEDs generally prove to be the ‘do-minimum’ option in most circumstances.
*Note – LED lighting is generally referenced in terms of colour temperature, expressed in Kelvin (K).
The Transport Agency is encouraging road controlling authorities (RCAs) to transition to LED lights by offering funding assistance.
LED lighting for councils is funded through the funding assistance rate (FAR), which is as much as 85 percent of the total cost of activity to be paid from the National Land Transport Fund (NLTF).
Councils will then be able to invest the money they would have spent on LED lighting on other transport projects within their communities.
For new build projects, the adoption of LED road lighting is a relatively straightforward exercise, but the Transport Agency has also been assessing the economics of accelerated LED replacement programmes for existing infrastructure.
LED lights are much cheaper to run, require less maintenance and have a much longer life time (typically 20 years compared to four years for high pressure sodium (HPS) lamps). International studies have found that LED lights help reduce urban road accident rates due to increased luminance from white lights, compared to the yellow light from HPS lights.
Converting to LED lighting has the potential to save up to 60% of the electricity consumed by conventional HPS lights. When these lighting assets are adaptively controlled through a centralised management system, for example through dimming, total energy savings can be up to 70%.
A present value calculation for the Tauranga Eastern Link estimates a payback period for LED lights of approximately 11 years. As a result, LED lights are the preferred technology for new installations on Transport Agency state highway projects.
We’re still learning about any potential risks LEDs may bring. Some articles published internationally have resulted in a number of misconceptions about blue light in relation to road lighting. Blue light is often spoken about in terms of exposure from sources such mobile phones, computers and television.
There is currently very limited evidence to demonstrate a significant health risk for road lighting from LED sources in relation to road lighting. A 2016 study by Public Health England has indicated reaching unsafe exposure limits for blue light risk would require someone to stare into a streetlight for 2.5 hours from a distance of two metres. Therefore, road users and pedestrians are unlikely to reach such exposure limits from LED streetlights.
There has also been some concern about increased light pollution – which is commonly referred to as ‘sky glow’ - in towns around New Zealand because of the switch to LED lighting.
The new technology will thus limit the amount of upward waste light we produce overall. Our target for design of less than one percent waste light is significantly less than the current Australian/New Zealand standard of up to three percent.
The Transport Agency’s goals align with the direction of many other organisations in regard to limiting light pollution, however these are not the agency’s core goal. The key reason we light our roads is for the safety of our customers – those people using the road network for personal and business travel - we don’t have the sole goal of providing dark skies.
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