Lighting : LIGHTING-June-July-2017
June/July 2017 | LIGHTING MAGAZINE 11 10 LIGHTING MAGAZINE | June/July 2017 Even if a path is not populated, if the lighting means that someone using the path is visible from a distance then there is an inherent natural surveillance and the risk to the criminal is increased. The lighting of a space may relocate the crime to another location but it does establish a safer option for people to meet and travel. Conversely, if a path leads to an area where there is no natural surveillance, for example a path between two high walls or a valley in a park, then it is probably better to not light the path. In this instance it can lead someone into an unsafe area, giving them a false sense of security, and in this situation the lighting probably only serves to assist the criminal to better select their victim. The second purpose is to assist the sense of personal safety. If the lighting of a path provides vertical illumination of people’s faces, a person has the opportunity to assess whether that person is friend or foe while there is still time to take evasive action. It is important that not just the path is lit but the surrounding area as this can reveal other people in the area. This can often be effectively achieved by under lighting of trees and the lighting of walls. This reduces the shadows and reveals the presence of people in the area without the need to blanket light the space. Selective lighting of primary routes encourages people to use the same route and therefore increases the natural surveillance. The quality of the lighting is just as important as the illumination levels. Unfortunately it is hard to specify quality in a standard. The greatest problem with public lighting is glare. Glare reduces the effectiveness of the lighting. As a result the space appears dark even though it is has adequate illumination. A common reaction is to increase the illumination, often compounding the glare. When glare is controlled distant views are improved and therefore the perception of security is increased while maintaining modest illumination levels. With modern outdoor lighting there is no reason why path lights should emit any light above the horizontal plane. Although glare control tends to reduce the spacing of the fittings it is well worth it in terms of increased visual performance. Security lighting is a much more difficult situation. There are no standards that specifically cover it. It comes under the scope of AS4282: Control of the obtrusive effects of outdoor lighting and may come under AS1680.5: Outdoor workplace lighting. Neither standard however give any guidance as to what is an appropriate level for security lighting. In 1997, the first edition of AS4282 was published. This has had a significant impact on the waste light and spill light into the sky. This is ongoing as refurbished installations are upgraded to comply. The standard is currently in revision and will address some of the shortcomings of the previous edition. We can all cite situations where public lighting has been installed without a thorough understanding of the issues. We can also quote isolated instances where, for various reasons, the lighting may have had a negative effect on the safety of people, but these are exceptions rather than rules. To draw the conclusion that “Until the lighting and crime issue is better understood and qualified, no more security lighting and other lighting supposedly for crime prevention should be installed” is an overreaction. The relationship between lighting and crime prevention is very complex and it is unlikely that there will ever be definitive study. The way forward is to use competent lighting designers that understand the interplay between light and people and to educate clients to have realistic requirements and expectations. Peter McLean, LFIES Chair, Standards Australia Committee LG-010 (Obtrusive Effects of Outdoor Lighting) Peter, Whenever articles are published on the real or perceived threats to safety in public spaces and the role of lighting, there is always controversy. Thank you for clarifying the issues involved and the difficulties involved in producing lighting Standards to “solve” the problems. I agree with the points you make about revealing not only, say, a footpath but the surrounds to the footpath and that crucial to success is the minimisation of glare to achieve good seeing conditions. I welcome other contributions on this important aspect of public lighting. Warren. Christchurch pedestrian crossing lighting upgrade I am writing regarding the article on the relighting of the pedestrian crossing in Christchurch in the April/ May issue (pp 44-50). This caused me to wonder if anyone ever reads the lighting research literature apart from the people who are employed to produce it. There have been a number of papers on the lighting of pedestrian crossings which indicate that the position of the luminaire is an important factor in making the pedestrian visible. In this case the designer was forced to use the existing columns so an opportunity to improve the lighting further was missed. The way to improve the visibility of pedestrians on a crossing is to increase the contrast of the pedestrian against the road. Bollard lighting can be designed to do this very effectively by increasing the vertical illuminance on the pedestrian without adding much to the luminance of the part of the road against which the pedestrian is seen by an approaching driver. Of course, lighting can only do so much. The most effective way to enhance the visibility of pedestrians on a crossing is to get them to wear light coloured clothing. Best wishes Peter Boyce, PhD, FSSL, FIESNA United Kingdom Peter,Thankyouforyourcomments,especiallywith regard to the retrofitting of LED luminaires on existing lighting columns. Higher glare often results, when using existing column spacings, because very high intensities, at high angles, are required to achieve the required road luminances. Pedestrian crossing lighting in New Zealand (and Australia) is illuminance based, often using floodlights mounted on outreach arms, directed from each approach side of the crossing, to increase pedestrian visibility. Your last point regarding pedestrians’ reflectances is not only important but interesting. It is surprising how dark most people’s night-time attire is compared with their daywear, in both winter and summer. It is often difficult to see pedestrians until they are on the crossing, so there can be little warning of danger. The problem is exacerbated by those who walk the streets, zombie like, staring at social media on their phones. Warren. 44 LI GH TI NG M AGA ZI N E| A p r il/May 20 1 7 A p r il/May 20 1 7|LI GH TI NG M AGA ZI N E45 TE CHNICAL FE A T U REC h r i stc h urc h pedestr ian cross in g li g h t in gupgr a de B y Yun y uZhu–L i ght i ng D e si gn Eng i neer, Connet i c s Ltd, N Z I N T RODUC TI ON In July 20 1 5, Christchurch City C o uncil d eci d e d t o carry o uta li g htin g u pg ra d e p r o ject, t o re p lace the 1 25W mercury va po ur (MV) an d s o me 1 50W metal hali d e (MH) luminaires with new L E D luminaires, at 23 p e d estrian cr o ssin g s.Asac o st e ff ective a pp r o ach, existin g c o lumns an d ca b le po siti o ns were t ob e utilise d . Determinin gf act o rs fo r the li g htin g u pg ra d e were: l S a f ety c o nsi d erati o n E xistin g MV an d MH luminaires f aile d t o achieve re q uire dp e d estrian cr o ssin g li g htin g stan d ar d s, which lea d t opo tential risk t od rivers an dp e d estrians usin g the cr o ssin gpo ints. l E ner g ye ff iciency an d maintenance c o nsi d erati o n E xistin g luminaires were i d enti f ie d as unec o n o mic t oop erate an d maintain, d uet o a g e an d ener g yc o nsum p ti o n,c o m p are d with m o ree ff icient L E D p r od ucts availa b le an d a ffo r d a b le in the market; als o ,MVlam p s are b ec o min gob s o lete which makes it una b le t o maintain them in the f uture. D ESI GN CR ITE R I A T he p e d estrian cr o ssin g s were o n Cate go ryVr o a d s o r b usy Cate go ry P r o a d s, there fo re in acc o r d ance with A S / N ZS11 58, P art 4 :li g htin gofp e d estrian cr o ssin g s, “X 1 ” was selecte d as the a pp lica b le li g htin g stan d ar dfo r this d esi g n1. T he re q uire d illuminance values are sh o wn in T a b le 1 (an excer p t of ta b le 3.5 f r o mA S /N ZS11 58, P art 4 ). PE D EST R I AN CRO SSI NG LAYOU T Instea dof ase p arate d esi g n fo r each cr o ssin g ,theC o uncil re q ueste d the use of three m od els t o re p resent all cr o ssin g s, d uet o the f act that all cr o ssin g s f ell int oo ne of the fo ll o win gd imensi o n g r o u p : 11 m (len g th)x5m(wi d th) 1 0m (len g th)x5m(wi d th) 7m (len g th)x5m(wi d th) D ESI GN ANALY SISI lluminance calculati o ns In o r d ert op r o vi d e a clear p resentati o n, h o riz o ntal an d vertical calculati o ns ex po rte df r o mli g htin gd esi g n s of tware, AGI32 (versi o n 16 .3. 1 3), are sh o wn in d ivi d ually in the p lan an d si d e views sh o wn in F i g ures 2 an d 3. T he values are maintaine d illuminances. All the values sh o wn in F i g ure2an d 3in d icate the cr o ssin g isc o m p liant with the S tan d ar d ’s re q uirements fo r S u b cate go ryX 1 . E ner g y savin g s As the result of the c o m b ine d li g htin g u pg ra d es,are d ucti o nin ener g yc o nsum p ti o n of 55% was achieve d (see T a b le 2). T his w o ul d save 1 2,775 kWh of ener g y annually, which w o ul d a dd u p t o 255,5 1 0 kWh o ver twenty years’ time — the luminaire li f eex p ectancy. O T H E R CON SI D E RA TI ON S Glare c o ntr o lan d U p war d Waste Li g ht Rati o (UWLR) As p art of luminaire assessment p r o cess, g lare c o ntr o lan d UWLR were im po rtant c o nsi d erati o ns, a dd resse db ym o untin g the luminaires at zer od e g rees an d selectin g luminaires with s p ecial op tics d esi g ne dfo r p e d estrian cr o ssin g s. Table 1 . Values o fli g ht technical p ara m eters (L TP )f o r New Zealan dP e d estrian Cr o ssin g s2 Li g htin g su b cate go ry Po int h o riz o ntal illuminance – Marke d cr o ssin g ( E ph) Po int h o riz o ntal illuminance – S urr o un d s( E ph) Po int vertical illuminance – Marke d cr o ssin g ( E pv) Glare c o ntr o l an d UWLR X 1 30 lux (measure do nr o a d sur f ace) 1 0 lux (measure do n p athway sur f ace) 20 lux (measure d1 m a bo ver o a d sur f ace) S ee Clause 3.3.5 Figu r e 1 . Typical pedest r ian c r ossing layout. ( N ote: d r awing is not to scale.) Figu r e 2. Within the ma r ked c r ossing a r ea ( 1 0m×5m),alltheho r izontal illuminances we r eg r eate r than 30 lux while within the su rr ounding a r eas (5m × 3m), all values we r e g r eate r than 20 lux. Figu r e3. V e r tical illuminance calculations. The magenta a rr ow indicates calculation point di r ection. A t each calculation point ( 1 m above r oad su r face) on the ve r tical plane ( 1 0m× 1 m), all ve r tical illuminances we r e above 20 lux, with the lowest calculated value being 20.6 lux occu rr ing at the mid-point of the c r ossing (fu r thest f r om the light sou r ce) which was expected.
LIGHTING August-September 2017