Meet the brains behind one of the ILP’s latest key documents: PLG08 Guidance on the application of adaptive lighting within the public realm
Talk by Nigel Parry, ILP Technical Committee
6. Ultra-Efficient Lighting
(UEL)
The adaptive lighting approach will essentially look to
help enable you to apply the principles of Ultra-Efficient
Lighting (UEL) which is defined as:
“Providing the
• right light, in the
• right place at the
• right time
and controlled by the right system”.
#ILPSummit
7. BS5489-1:2013 for the five step design
process, the steps being as follows:
Step 1 Select lighting class
Step 2 Risk assessment
Step 3 Adjust lighting class
Step 4 Consider S/P ratio
Step 5 Consider adaptive lighting
BS5489-1:2013
#ILPSummit
8. Comparable lighting classes
based on BS5498-1, 2013
ME Class CE Class S Class Required
average
illuminance (lux)
% dimmed
compare to
above class
- CE0 or C0 - 50 -
ME1 or M1 CE1 or C1 - 30 40%
ME2 or M2 CE2 or C2 - 20 33%
ME3 or M3 CE3 or C3 S1 or P1 15 25%
ME4 or M4 CE4 or C4 S2 or P2 10 33%
ME5 or M5 CE5 or C5 S3 or P3 7.5 25%
ME6 or M6 - S4 or P4 5 33%
- - S5 or P5 3 33%
- - S6 or P6 2 33%
#ILPSummit
9. Adjusting the lighting class
The British and European Standards allow illumination
levels to be varied depending upon the category of
road and its usage. Therefore illumination levels could
be reduced when traffic flows are lower.
Lighting could also be increased as a crime reduction
measure, say outside night clubs for a defined period
after they close.
#ILPSummit
10. What is adaptive
lighting?
The term used do define the operation of the lighting during the
periods of darkness. It includes:
• Compensation for design maintenance factors
• Trimming
• Adjusting the lighting class based upon highway/area use or the
tasks being undertaken
– For highways this may be a reduction in lighting class
– For areas around entertainment venues this may be an
increase in lighting class when such venues close
• Part-night lighting or Switch off.
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11. Looking at Adaptive
Lighting
Compensation for design maintenance factors
is where the maintenance factor is simply designed out
through the application of constant light output across the
design maintained period
“Trimming”
is where currently the majority of public lighting switches on
when ambient light levels fall to 70lux and switches off when
the ambient level rises to 35lux. This was a standard
approach that allows time for lamps to ‘warm up’ and reach
their required operational output.
#ILPSummit
15. 15
Maximum
Average Hourly
Flow
Average
AADT
BS5489
Traffic
Flow
ADT
Correction
Factor
Traffic figure
trigger point
BS5489 Lighting
Classification
262 2429 Very Low <7000 ME5
436 4502 Very Low <7000 ME5
1276 14875
Low to
Moderate
7000 to 40000 ME3b
Very Low 7000 0.471 601 ME4a
384 3802 Very Low <7000 ME5
1642 20705
Low to
Moderate
7000 to 40000 ME4a
Very Low 7000 0.338 555 ME5
1478 19652
Low to
Moderate
7000 to 40000 ME4a
Very Low 7000 0.356 527 ME5
4576 61793
High to Very
High
40000 ME2
Low to Moderate 40000 0.647 2962 ME3b
Very Low 7000 0.113 518 ME4a
BS5489:2013 Table A2
Duel Carriageway High Density
BS5489:2013 Table A3
Single Carriageway
BS5489:2013 Table A3
Single Carriageway
BS5489:2013 Table A3
Single Carriageway
BS5489:2013 Table A2
Single Carriageway
Essex: A414 EDINBURGH WAY
E of A1019 Fifth Ave
Essex: FIRST AVENUE
HARLOW E of A1019 Fifth Ave
Essex: A127 RAYLEIGH - EAST
OF RAYLEIGH WEIR
113
114
115
116
117
118
49
No dimming possible as road is lit to the lowest possible level in accordance with BS
5489-1:2013
No dimming possible as road is lit to the lowest possible level in accordance with BS
5489-1:2013
ADT Classification
Site
Essex: RYE HILL ROAD
HARLOW 358m SE of Longwood
Essex: PARSLOE ROAD
HARLOW
Essex: WATER LANE HARLOW
Essex: HARLOW ROAD
ROYDON
BS5489:2013 Table A3
Single Carriageway
BS5489:2013 Table A3
Single Carriageway
Lighting Class reduction when
AADT reduces to
Lighting Class reduction when
AADT reduces to
Lighting Class reduction when
AADT reduces to
Lighting Class reduction when
AADT reduces to
No dimming possible as road is lit to the lowest possible level in accordance with BS
5489-1:2013
#ILPSummit
19. #ILPSummit
The graph below shows the daily and
7 day average ADT for a 52 week
sample of data on the A303 near to
Stonehenge
19
20. #ILPSummit
The following graph shows the daily and 7
day average ADT for a 1 week sample of
data on First Avenue, Harlow. First Avenue
is a two lane single carriageway with a
40mph speed limit.
20
21. #ILPSummit
The graph below shows the daily and 7 day average ADT
for a 2 week sample of data on First Avenue, Harlow. This
is a two lane duel carriageway with a 50 mph speed
limit.
21
23. #ILPSummit
What does it look like?
M1 J21 to 21a showing the centre reservation dimmed from 100%
down to 35% to show the maximum effect of dimming from
2cd/m2 to 0.7 cd/m2
24. #ILPSummit
Not all Light Sources
are the same
100.00%
20.00%
50.00%
10.00%
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
SOX SON CPO LED
Full
Max dim
25. #ILPSummit
Summary
For 95% of the roads
assessed, the lighting can
be reduced to the next
class at 22.00 hrs. each day
with the lighting being
increased back to full
output from 06.00 hrs.
25
The majority of roads
reviewed have shown that
only a reduction of one
lighting class is applicable
under BS 5489-1:2013
although in some instances
a reduction of two lighting
classes is achievable.
This is essentially considered a ‘safe rule of thumb’ and suits the
majority of cases looked at which statistically can be considered as
a representative sample across the UK.
Editor's Notes
Now, more than at any time in the recent past all Local Authorities are under pressure to reduce their energy bill and with many Local Authorities, Public lighting requirement representing at least a third of the their energy commitment and street lighting can be seen as an easy target.
To support the Lighting Industry in the application of good practice regarding the employment of energy reduction strategies and technologies.
A guidance to that will help Lighting Services to consider all of the implications that will be relevant when implementing various strategies.
This can be a good thing providing an injection of capital to apply innovative invest to save project however LA’s can be applying various strategies some born from a requirement to reduce revenue cost rather than aligning to the requirements of Ultra Efficient Lighting ’providing the right light, in the right place at the right time and controlled by the right system’.
BS5489-1, 2013 advises us of a 5 step strategy to help us understand
Step 1 – the tables within BS5489-1 make general assumptions about the environment and activities within which the road lies.
Step 2 – requires the area to be actually reviewed to determine the nature of the area and how the road is used
Step 3 – requires you to consider the finds of step 2 and through a risk assessment / appraisal adjust the lighting class in stage 1 to suit actual conditions
Step 4 – only applies to subsidiary roads, adjusting the level to suit the S/P ratio
Step 5 – this relates to this report and requires the designer to consider if the task changes during the night and thus can adaptive lighting be used, as such adaptive lighting is applicable to all forms of exterior lighting under Bs5489-1:2013.
It should be noted that at all times a defined lighting class must be achieved, this is stated within the Standard.
So we need to understand the lighting classes that are applicable to your design and the difference in classes and then ensure that you have the technologies to enable movement between them.
Stepped ballast, CMS controlled ballast/driver etc.
While this step is straight forward and your choice of equipment will largely depend on what you wish to achieve for your network within in whatever budget constraints you have, the major problem has been understanding who you can identify when you can adapt the lighting.
Adaptive lighting whereby lighting classes are set appropriately to meet the requirement for the conditions at a particular time of the night and thereby are applied according to street activity rather than remaining at a pre-determined level. This should reduce the energy bill yet still provide the required levels of illumination on the street, area or car park.
Varying lighting levels are based upon highway and / or area use by all users and include considerations for the following.
For highways this may be a reduction in one or more lighting classes.
For areas around entertainment venues this may be an increase in lighting class when for example such venues close.
And by now we are all aware of the benefits of light sources with Ra’s > 60 more info is available within TR29 and PLG03 (available at all good lighting institutions)
There is much evidence that shows that white light (defined as having a colour rendering index of Ra 60 or higher) improves perception and that if it is used then lighting levels could be reduced without perceptible impact on a person’s vision.
The research is summarised in the ILP Reports TR29 White Light and PLG 03 Lighting for Subsidiary Roads:
Lighting design has always been undertaken to address the worse case however the conditions of the worse case say 6 o'clock on a Decembers evening (rush hour) may only last for a couple of hours which effectively means that we could be over lighting the highway for 80+% of the time. In fact for most of the year the conditions that require the traditional design lighting level may not even exist within the hours of darkness. So applying the principles of UEL, if we can understand what the lighting class is at any time then the correct lighting solutions can be applied.
OK that great, but how do we know what the lighting class is at any give time?
Well the British and European Standards allow illumination levels to be varied depending upon the category of road and its usage. Therefore illumination levels could be reduced when traffic flows are lower, for example between midnight and 5am and still provide the right lighting for all road users. Lighting could also be increased as a crime reduction measure, say outside night clubs for a defined period after they close.
So maybe time to look at lighting design in a slightly different way.
BS 5489-1:2013, allows lighting during different periods of night to be classified differently.
Type of road
Traffic flow, either by flow rate or as a percentage of carriageway design capacity
Presence of conflict areas
Presence of traffic calming features (in general horizontal deflection)
Crime risk
Ambient luminance levels
Social and economic considerations
Security considerations
Adaptive Lighting is the term we are using to describe any change to a lighting solution whereby a lighting solution changes in it basic operational status throughout its operational period, this may be through
Compensation for design maintenance factors
Trimming
Adjusting the lighting class based upon highway/area use or the tasks being undertaken
For highways this may be a reduction in lighting class
For areas around entertainment venues this may be an increase in lighting class when such venues close
Part-night lighting
Switch off.
We now have access to the control equipment to cover all adaptive lighting scenarios from Switch off through to full dynamic adaptation.
We now have the technologies readily available to deliver almost any adaptive lighting strategy that may be appropriate.
From simple “Switch off” through to fully interactive dynamic solutions adapting to the environmental requirements at any given time.
Compensation for design maintenance factors we can look to ‘reverse engineer’ the project Maintenance Factor over the period of the lamp installation life (say, four years) effectively reducing the lamp by 25% at the outset of the installation and then over the lamp ( light source) installation life adjust lamp output to compensate for the reduction in light output and luminaire dirt build up. This will ensure that the correct lighting level is provided on the highway / public area and reduce the electrical load of the installation and allowing for performance tolerances by around 20%.
Trimming came around due to the need to save energy but also due to the awareness that modern lamp sources and control gear take less time to warm up to full output once switched on than older sources with magnetic control gear. Consideration was also given to “why do we turn all lights on at 70lux when for example the street is only required to be lit to 10 lux?” Essentially the lighting is up to full output before the ambient lighting levels have fallen to the level required by the artificial lighting installation.
Next Slide
Table A.2 of BS 5489-1:2013 and shows how the lighting class can be varied depending upon traffic flow
Where adaptive lighting is applied on main and principal routes it may be necessary to give due consideration to be able to override the switch off in the cases of:
Accidents
Road works (lane restrictions, diversions)
Events.
The footnote associated with Table 2, Traffic flows within BS 5489-2:2003 +A1:2008 Code of practice for the design of road lighting —Part 2: Lighting of tunnels enables the designer to undertake an assessment of peak hourly flow against daily traffic flow as follows.
The note states:
If the actual value is not known, peak hour traffic can be derived as follows. Average daily traffic (ADT, vehicles per day) is the most used concept in traffic planning and it is always known. Peak hour traffic (vehicles per hour) is in rural areas 10 % and in urban areas 12 % of ADT. On undivided roads, the number of vehicles per hour per lane can be calculated by dividing peak hour value by the total number of lanes.
The challenge facing the production of this guidance was to provide “simple clear guidance” , a year ago we appealed for traffic flow data and we did collect and collated a fair amount of this info
The panel look at the data and applied it to a “time and traffic flow” graph and these roads as do most we looked at have a similar profile which we considered could become a generic time profile for adaptation.
However this is not straight forward
The PLG08 panel has considered if a generic profiling assumption based upon sample data for a large range of roads for traffic use may be attainable and relevant
It should also be noted, as can be seen from the following charts, that the daily flows within a section of highway will also vary depending upon its place within the road hierarchy and the day of the week.
Monday evening to Friday morning traffic flows are in general very similar as weekday commuters travel to their place of work. On principal routes, higher traffic flows exist for longer on Friday and Sunday nights and to a lesser degree on Monday morning, due to long distance commuters as shown on the graph for the A303 below.
The traffic flow on local routes between Monday and Thursday are comparable with subtle variations on a Friday and Saturday night due to nightlife activities.
The weekend flows are generally different, with lower flows in the morning and evening and a peak flow during the middle of the day.
This permits a clearer view of the traffic flow and a more accurate assessment of when the variation in lighting classes can be applied. The same principles for the trigger points are used as before and follow the same application of the lighting classes.
The 7 day average ADT has been included to show the effect of combining the ADT for all 7 days has on the distribution. The traffic data provided for these sites are between whole hours, e.g. 01:00 till 02:00 therefore the data has been shown at the half hourly point. The yellow portion of the chart indicates mid-winter and the light blue mid-summer.
We are trying to ensure that we explain data like this where annual cycles are understood and the correct lighting classes applied for the task
The top graph indicates the peak flow rate is in the daylight hours trigger points for class variation is 7am and 8.30pm
&
The second graph traffic flow only reaches the intervention between 5 & 7pm
These are only snap shots of two particular sections of highway however we have hopes that the theory behind this can be employed to deliver a simplified approach.
Using the traffic data in a tabular form and applying conditional formatting it is possible to identify which lighting class may be applicable for each hour throughout the 24 hour period. However the information is of course primarily used to identify when the trigger point is reached.
The results show that generally for each road on a Monday to Friday the changes in lighting class can be applied at the same time. However, the times are different over the weekend with both Saturday and Sunday changing lighting classes at different times.
What can be seen from the tabular method of showing the times that lighting levels can be varied is that only hourly assessments can be made. Where there are subtle variations a better assessment can be made using graphs.
A point worth clarifying is that the correction figure is applied to the daily traffic flow figures which are used to work out the ADT. This is shown in the following graphs. The arrow points towards the peak corrected average ADT equivalent for 7,000 or 40,000 ADT respectively.
The graph for the A127 at Rayleigh shows that the lighting class may be varied by two classes. The first reduction in lighting occurs when the last traffic flow on a Friday crosses the trigger point at 19:30. The second reduction in lighting class occurs when the last traffic flow crosses the trigger point on a Sunday morning at 02:00. In reverse, the first earliest switching point where the lighting class should increase occurs when the first traffic flow crosses the trigger point on a Monday to Friday morning at 04:30. The second earliest switching point where the lighting class should increase occurs when the traffic flow crosses the trigger point on a Monday to Friday morning at 06:15.
During the long summer days the traffic flow is such that the full lighting class is not required during those months, also during the longest days the lighting is extinguished before it returns to its first reduction in lighting class. During the winter months the flow is such that the full lighting class is required
The application of adaptive public lighting and the application of a responsible energy management strategy according to road usage is clearly an energy saving approach that requires due consideration. The Standards permit the lighting levels within the public areas and highways to be changed depending upon use and the task to be lit. Therefore a system that ensures the right lighting levels are applied at the right times will bring about maximum energy savings whilst still providing the required level of service to the public without compromising safety. The following approach taken from Annex A of BS 5489-1:2013 should be followed when considering the application of lighting to any public area:
Step 1 Select the benchmark lighting class from the relevant BS 5489 table
Step 2 Carry out a risk assessment to identify specific lighting needs for the road
Step 3 If necessary, adjust the lighting class up or down based on the assessed risks
Step 4 Adjust the lighting level according to the light source being used (S/P ratio) when the light source has an Ra > 60 and is a subsidiary road only
Step 5 Assess the lighting requirements to judge whether different lighting classes are applicable at different times of the night due to changes in traffic or pedestrian use
In summary, the application of adaptive lighting should consider:
BS5489-1:2013 & BS EN 13201:2003 permit variable lighting levels by permitting a road or area to be classified depending upon the use of that road or area at any given time
Positive cost benefit required
Reduction in energy
Lighting for safety must be considered and it is imperative that the safety of the user is not unduly compromised
If there is any doubt, then full lighting should be maintained at all times
The risk of crime is unlikely to change as traffic flows change
Considerations for increasing lighting levels are defined times based upon crime risk e.g. outside nightclubs, pubs etc.
The panel has found through the analysis of the information previously described that for 95% of the roads assessed, the assigned main lighting Class can be reduced to the next class at 22.00 hrs. each day with the Class being increased back to full output from 06.00 hrs.
The majority of roads reviewed have shown that only a reduction of one lighting class is applicable under BS 5489-1:2013 although in some instances a reduction of two lighting classes is achievable.
This is essentially considered a ‘safe rule of thumb’ and suits the majority of cases looked at which statistically can be considered as a representative sample across the UK.