Helsinki Case Study

Human Centric Road Lighting Installation.

With the impact of the colour temperature of white light effects on the human system, the City of Helsinki, Finland has recently installed nearly 2klm of LED streetlights that change colour temperature during the night to address this concern.


The City of Helsinki organised the ‘Lights over Kruunuvurenranta’ design competition for the artistic lighting of the new Kruunuvurenranta residential area. The competition was part of the World \design Capital Helsinki 2012 programme which aimed to promote the cities development through design. On 10 October 2012 West8 with Speirs and Major designers working with light had been announced the winner of the Lighting Master Plan for the future Urban development Kruunuvurenranta in Helsinki.

On the site of a former Oil harbour, a new residential development with some 10,000 dwellings will be constructed. The Lighting master plan will give guidance to the development of Kruunuvurenranta by creating a functional lighting plan and introducing an attractive nightscape seen from a distance.  Both the proposed landscape and illumination plan anticipate on the natural sources in terms of quality of darkness, use of local materials and site heritage.

By emphasising the natural scenery, a strong sensation of being in Kruunuvurenranta will be created. The water surface provides a highly reflective foreground which when fluid will create a broken, animated reflection of the lit image of the waterfront – in effect almost doubling the perceived quality of light present when viewed from across the water. Light will therefore be minimised and be used sensitively to reveal gateways, heritage features and selected neighbourhood lantern pegs.

The plan also referred to the appropriate colour temperature of the light source during the darkness of the long winter nights and how this can affect our activities, moods and behaviour. The City of Helsinki had been looking to try out this innovative approach and worked with OrangeTeK to develop a luminaire that could adequately light the highways and footpaths on the island to provide a change in the colour temperature during the night.

Circadian Rhythms.

Professor Russell Foster, who led the pioneering team at Oxford University which discovered the eye’s third photosensitive cells has explained that that the non-visual receptor or the intrinsically photosensitive Retinal Ganglion Receptor (ipRGC) is responsible for melatonin release from the pineal gland,

In undertaking his research Prof Foster and his team at Oxford were following up on a discovery back in 1923 that the pupils of blind mice still responded to the presence of light.

The idea that, if the rods and cones weren’t doing the work, something else must be, led the team to the discovery of the ipRGC which, in turn, led to the linkage between light and the effect that it has on our body clock – what we now all know as the circadian rhythm.

Further study went on to identify the light conditions that are necessary to trigger the ‘melanopic response’ within the pineal gland and that Blue light, as we get on a bright summer morning is key to resetting our body clocks and ‘kick’ starting the day

Much work has been done on this for interior lighting, but this project takes the approach to the outdoor highways environment for the first time.

Technical Solution.

The location is a busy arterial route to the island suburb and has the usual two-lane highway, running parallel to a mixed foot-path and cycle-path. Helsinki required a minimum average of 1cd/m2 (EN13201-M3) on the highway and 7.5lux(P3) on the cycle/footpath to be achieved at any given colour temperature from 3000K to 5000k. The existing 10meter high columns were positioned about 35metre apart single sided on the non-footpath side of the roadway.


Roadway Lighting – M3 Initial design

CAT Required 3000k 5000k

















Uo W





Foot/Cycleway P3 Initial design

CAT Required 3000k 5000k









E min/max





To achieve this performance some additional work to a standard Ignis2 luminaire was required.

Firstly, we had to be able to deliver the lighting performance using just the warmer (slightly less efficient) 3000K chips, so do this we used the Osram Square chip with its very high lumen per watt and extremely good lumen depreciation rate even at higher operating temperatures.

A solution of 72 LEDs driven up to 700mA would provide the lumen package. The same arrangement for the 5000k would work even better.

This would require a total of 144 leds with lens to be housed with twin drivers. To achieve this in a reasonably lightweight, compact lantern we chose the double up the LEDs per lens, to have a twin set arrangement. Thus, a new lens was required to accommodate the twin LED chips and provide the lighting as required.

In addition to the unique configuration and colour change, dimming was also required during the night when traffic is very low and thus make energy savings beyond that achieved by changing from the existing from 250watt high pressure sodium lamps.

The configuration agreed for the first installation follows with options for dimming levels and times:

Street scene

Yearly night

23:00-00:00 is 25%


01:00-05:00 is 50%

Early morning

05:00-07:00 is 25%

Light traffic

Late evening

23:00-00:00 is 40%


1:00-05:00 is 60%

Early morning

05:00-07:00 is 40%

With the following colour temperatures during the hours

Early afternoon

14:30-17:00 is 5000K

Late afternoon

17:00-17:30 gradually shifting to 3000K

Early evening

17:00-17:30 gradually shifting to 3000K


21:00-21:30 gradually shifting to 4000K

Late evening

21:30-23:00 is 4000K

Yearly night

23:00-23:30 gradually shifting to 5000K


23:30-05:30 is 5000K

Early morning

05:30-06:30 gradually shifting to 4000K


06:30-08:00 is 4000K

Late morning

08:00-10:00 gradually shifting to 5000K

When running the design simulations is was noted that the 5000k option, slightly over lit the road when compared to the 3000k and thus the 5000k driver maximum output was choked back by about 5% to keep the light levels similar.

Initial approach was to have the control pre-set and to run the same every night. However, as the development progressed a more flexible approach was sought and to be able to deliver this, wireless control was deemed the best solution. The C2Smartnode was already the choice for Helsinki and thus utilised for the lantern.  Although the Smart node usually only has one Dali output, it to control two Dali drivers. Thus, the answer was to have two separate Dali addresses controlled from the single C2 output. Some off-site testing was carried out to ensure the functionality was comprehensive to have easy control.

The lights were installed earlier this year. together with the C2 CMS system onto the existing lighting infrastructure. The installation and testing was easy and straightforward with the shifting colour temperatures seamlessly blending to the required outputs. As the nights are still short, the real test will be the first winter, when the lucky residents will be some of the first people in the world to benefit from this human centric approach.



Colour temperature.