LED retrofit of 1,240 public lighting points with a road lighting design

Swapping the lamp is not a design

The contract carried 1,240 identical LED luminaires, mounted on existing brackets over existing poles. A night survey with a lux meter showed what the purchase specification did not: two avenues with poles every 22 m already ran above the required level, while one neighbourhood stretch had twisted brackets, a 6.8 m mounting height and luminaires aimed at the facades rather than at the road.

Classify before choosing

• Every stretch classified by road family under NBR ISO/CIE 8995-2, with speed and pedestrian flow stated
• Night measurement of mean illuminance and uniformity at 46 points, at the same hour, with no traffic
• An inventory of the control circuits: mercury-welded contactors, relays that never dropped out and two boards with no RCD
• Checking the earthing of brackets and control boards, with continuity measured pole by pole on the pilot stretch

The outcome was not uniform: where there was excess, the old luminaire stayed until the end of its service life and only the control circuit changed; where light was missing, power went up and the aim was corrected. After two bills on the pilot stretch, metered energy had fallen 46% and the mandatory levels were met at all 46 reassessed points. The report became a contract annex and the design, the basis for enforcement metering.

Cost-effective public lighting is not the cheapest luminaire in the tender: it is the one that lights the pavement that needs it, and not the window of whoever lives below.