Fears for 'dark sky' ambitions

Richard Saunders
Richard Saunders
The Dunedin City Council is pressing ahead with new 3000-Kelvin street lights for the city, despite concerns it might spell trouble for the city's ''dark sky'' ambitions.

A report to next week's infrastructure services and networks committee meeting shows the council has called for tenders to carry out the city's $13.1 million street-light upgrade.

That included the type of LED lights to be used, which would be 3000K in brightness - higher than the 2400K lights some submitters had argued for.

Council staff had previously assured councillors they would have the final say on the type of lights to be used, but the report offers no options, saying ''this is a report for noting only''.

Council transport group manager Richard Saunders said yesterday the decision was based on an earlier vote, in mid-2017, which authorised 3000K lights.

Staff were ''comfortable'' the current project, including the 2017 decision, would provide ''the best-balanced solution for our LED renewal'', he said.

Despite the ''for noting only'' recommendation, councillors could still opt for a different approach, he said.

''This report does give the councillors a chance to review that decision and they could resolve something different to the 2017 report.''

Dunedin Dark Skies Group member Kyra Xavia said while 3000K was better than 4000K, the group wanted a softer, amber LED light of 2700K for arterial routes and 2200K elsewhere.

The lower-temperature lights were increasingly becoming the ''standard'' overseas, as more was learned about problems associated with LED lights, including the impact on human and animal health, she said.

Fellow member Michael Broughton said the NZ Transport Agency had already funded 2200K lights in the Mackenzie district, which had an International Dark Sky Reserve, and there were similar aspirations for Dunedin.

To qualify, lights had to be a maximum of 3000K, but the International Dark-Sky Association was revising guidelines, down to a maximum of 2700K, he said.

The report to Monday's meeting noted the council's plan would adopt three key recommendations from the international association.

The association's recommendations were: lights of no more than 3000K; dimmers; and shielding to limit light pollution.

While 3000K lights would be a step towards dark sky accreditation in Dunedin, other light sources - including from residential and commercial buildings - would also need to comply, the report noted.

The 3000K lights would be slightly less cost-effective to buy and install, and slightly more expensive to operate, than 4000K lights.

However, both still offered significant savings - worth about $300,000 a year in reduced energy costs - compared with the city's ageing high-pressure sodium lights.

Tender documents also left room for future changes, including lights with lower colour temperatures in some parts of the city, Mr Saunders said.

The upgrade was due to begin next year and be completed in 2020-21, and 85% of the cost would be covered by an NZTA subsidy.



For pedestrians, diminished lighting in this town invites GBH, back of the nut with a crowbar.

So it'll take 50 years to recover the costs provided the money isn't borrowed. That's a very long time for an infant technology whose cost is dropping fast.

Good on Kyra for recognising the link to our well being on seeing the sky.

A note for the editor : Kelvin is a unit of colour in this case, not brightness. It's confusing, because it comes from a unit of temperature. The higher the number, the bluer the light, not necessarily the brighter.