Many people jump into lighting design software without considering the road or street user needs. This webinar describes considerations the designer needs to accommodate, prior to opening the software or situation analysis as it has been referred too, but also review some of the issues that occur in the design process. Changes in the recently released BS5489-1:2020 will also be discussed in a Question and Answer session hosted by ILP Birmingham at the end of the webinar.
This webinar is a precursor to the launch of the ILP online training course ‘Good Practice in Lighting Design’ and follows on from the previous BS5489 launch webinar in June of this year. The course will be available from the ILP training platform soon, with discounts for ILP members. It should be noted, this will not be a software training course that Nick usually delivers.
Speaker: Nick Smith FILP IEng MIES, Nick Smith Associates Limited
Hosted by: Kieron Jarvis, Vice Chair and Ryan Parry EngTech AMILP, Education Representative for ILP Birmingham
Q&As
| Question | Answer |
| Is tilt the same as uplift? | Yes, though tilt often refers to the lantern whereas uplift tends to refer to the bracket arm. Tilt should, therefore be the overall effect of the bracket and lantern. |
Would you need to use tilt on a luminaire on steep hills? | On steep hills, you could consider rotation of the lantern rather than tilt. However, in practice, this would need to be very steep to be considered. |
With the acute cut off of LED’s a small tilt is often required to save using a high output, is there another option to get round this issue? | Any uplift of a LED lantern is likely to cause significant problems with glare and obtrusive light. LED lanterns are available in a vast variety of settings so an alternative setting to overcome this should be available. |
Will Lighting Reality ever be updated to the point 3D obstructions can be built into the software within area calcs (e.g., Houses, buildings) and also incorporate the ability to use vertical masking? | Sorry, we can’t comment on this. Please contact Lighting Reality. |
| If variable lighting is used what percentage dimming is best to use? | The dimming should always be based on known outcomes rather than an arbitrary value so the dimmed amount should relate to a lighting class reduction. |
Is there a preferred colour temperature for lighting in ecologically sensitive areas? | Research suggests warmer colour temperatures are less damaging. Colour temperatures of less than 3,000K are now being used, with 2,700K and event 2,400K becoming more common. |
| If street lighting is exempt as a statutory nuisance, why is the protection of bats protection different? | Local authorities have some power to regulate light emissions. Technically street lighting is no exempt as a statutory nuisance but it would be difficult to enforce. However, in order to amount to a statutory nuisance, the emission must be ‘‘prejudicial to health, or a nuisance’’. This sets a high threshold, and one that is focussed on the impact of light emissions on humans, rather than the environment. Bats are protected by UK and European laws that protect them from intentional or reckless disturbance something that is easier to enforce. |
Street lighting road parameters needed to be justified as the standards like the M4 with the spacing between the pole and height of mounting, where we are replacing the LED from normal lighting, so we can do the tilting the fixture to 5 degree to justify the road standards? | The Standards are only recommendations, departure from these need to be considered by a competent professional and a judgement made. Uplifting a lantern will cause more glare and in a traffic route situation is likely to exceed the Threshold Increment parameters. |
Do you discuss the justification for lighting in the course? | The course does not discuss the justification for lighting but does discuss variable lighting and part night lighting techniques. |
What are the implications of the revised BS and how may this affect a Local Authorities lighting levels? | The revised BS5489 will not necessarily affect local authority specifications. The risk assessment process allows flexibility for the lighting professional to use their judgement to suit the site conditions. |
How can we educate the clients for the necessity of control for outdoor lighting? We have proposed recently outdoor lighting with astronomical clock and DALI dimming but the client is reluctant to implement any control because of the additional cost. | Tighter controls through planning and enforcement, better education of the general public and product information relating to product selection and installation are essential. |
What software do you use for external lighting other than Relux and DIALux? | There are many lighting design software packages available, the choice depends on the application and the extent of the sophistication needed. |
What measures is the industry undertaking to ensure that Best Practice is adopted? | Best practice will depend on education of products, standards, guidance and technical reports. Mainly, it will be determined by clients knowing what the levels of competence to insist on. |
| For lighting class determination, what justification could be used for levels lower that prescribed in the Standard? | There is no justification for an arbitrary use of lower lighting requirements than the Standards prescribe. However, a lighting professional after undertaking a risk assessment or situational analysis, may conclude, using their engineering judgement, that there is evidence to justify reduction in lighting levels. |
| What is the impact from the revised BS on the future pedestrian and cycling infrastructure? | The need for lighting should be assessed and PLG23, produced by ILP, should be used in conjunction with BS5489 to determine the appropriate lighting requirements, having taken account of the user groups, the environment and the complexity of their visual task. |
What distance should there be between conflict areas to prevent creep? | There is no hard and fast rule here. I would look at the 5 second rule distances described in PLG01 and PLG 02 as a starting point and their frequency. |
How come there is no differentiation between Normal and Quiet roads in Table A.5, like there is between Busy and Normal roads? There were different classes for Normal/Quiet in the 2013 code? | The designer needs to consider the usage of the area and carry out a risk assessment based on their knowledge of the area. If the designer does not think this is right then the class can be changed and reasons documented. |
| Why don’t you use just one big calculation grid for a whole estate? | Using one big calculation grid can distort the uniformity of lighting distribution. When calculations are made the lowest levels are highlighted but other similarly low lighting levels will not necessarily be indicated. As a result, one part of the grid area may have a much lower average than another part. |
Is it permissible to illuminate the underpass or under bridge areas with the RGB uplighters or wall washers ? | Account would need to be taken of the visual task and ensuring those needs are satisfied with this approach and that issues such as glare are accommodated. |
| What is the impact on energy with the removal if S/P ratios? | The change in the use of S/P ratios should not make a big difference as there is more scope for a risk assessment or scheme situational analysis to be carried out by a competent lighting professional. |
| Would unified glare rating (UGR) by a good measure for subsidiary road lighting glare control? | Unified glare rating are normally associated with interior design but there is a similar option available that is often used in sports and area lighting called glare ratings (GR). In theory it could be used in residential lighting but simply considering the TI% in the roadway design, normally this just a question of ticking a box to include it in most software, or the luminous intensity class if TI% cannot be calculated, but it can! Why would you not want to know what you are about to install? |
| How feasible is it to calculate TI for a residential road? | In road lighting design software, it is usually possible for TI to be included in the subsidiary road lighting report simply by selecting the TI tick box. This will give an added parameter to assess the impact of the scheme, so why wouldn’t you? |
The Lighting class selection process and table A.5 are based upon the light source having an S/P ratio more than or equal to 1.0. for any such source, the updated guidance is not to make an adjustment for S/P ratio. using the new standards is S/P required? less than 1 | Where the light source S/P ratio is equal to or greater than 1, no adjustment is needed in the current version of BS5489. However, where the S/P ratio is less than 1, the lighting requirements need to be increased to accommodate the reduction in vision. |
| Isn’t light intrusion subjective to an individual and/or groups of people age related? | It is true that light sensitivity changes with age. The Standards tend to be based on the vision of a relatively young person meaning getting the lighting right is so important and shouldn’t be based on anything other than sound engineering judgement. |
| Do you include a spill light zone in your grid to ensure the spill is minimised? | Spill light is used in luminance design used for traffic routes; this is known as Edge Illuminance Ratio (formerly surround ratio). These designs use a grid taken from kerb to kerb so the footways are accommodated by the EIR. For illuminance grids used for subsidiary roads the grid is taken from the edges of the area to be lit. An overview is covered on the course. |
| How important is uniformity of the light to reduce light dark light dark stripes and are the values provided? | Uniformity is very important to our vision. The four elements we need to see are brightness of the object, size of the object, time to see it and contrast. Contrast is the same as uniformity if this is too great the eye may not adapt and therefore you may not be able to see. |