Across the United States, there has been a rise in the phenomenon of purple streetlights. These purple streetlights, observed in cities like Tampa, Vancouver, Wichita, Boston, and Albuquerque, are actually blue LED lights with a phosphor conversion. The phosphor coating on the LEDs is responsible for creating a high-quality white light ideal for street lighting. However, in some cases, the phosphor has failed or come off, resulting in the lights emitting a deep blue spectrum, which appears purple to human eyes. The majority of LED street lighting in North America is manufactured by Acuity Brands, and starting around 2017, they began manufacturing defective lights. The exact cause of the defect is unknown, but it leads to the abrupt failure of the phosphor after approximately five years, resulting in the purple streets we see today. Acuity Brands is offering replacements for these defective lights, but the process of identifying and replacing them is lengthy and requires coordination with street lighting operators. While there is speculation about a blacklight surveillance network, the more likely explanation is the failure of the phosphor on the LED streetlights. Cities and electrical utilities are advised to report and replace these purple lights. Additionally, outdoor LED lighting is prone to other failure modes, such as flashing, which can be caused by driver issues. Overall, the rise of purple streetlights highlights the importance of quality control and maintenance in LED street lighting systems.
| Signal | Change | 10y horizon | Driving force |
|---|---|---|---|
| Purple streetlights appearing in cities across the US | Technological and aesthetic change | More advanced and efficient LED streetlights, improved color rendering, better durability | Technological advancements in LED lighting |
| Increase in the use of phosphor-coated LED lights | Technological change | Widespread use of phosphor-conversion white LEDs for street lighting, improved quality and energy efficiency | Cost-effectiveness and energy efficiency of LED lighting |
| Failure of phosphor coating in LED streetlights | Technical failure | Improved manufacturing processes to prevent phosphor delamination and failure | Lack of quality control in the manufacturing process |
| Monopolization of LED street lighting by Acuity Brands | Economic and market-driven change | More competition and diversification in the LED street lighting market | Acquisition and consolidation of lighting companies |
| Use of smart streetlighting solutions to monitor and detect failures | Technological change | More efficient and accurate detection and replacement of faulty lights | Adoption of smart city technologies |
| Flashing and cycling failures in LED outdoor lighting | Technical failure | Improved design and durability of LED lighting drivers | Prevention of driver malfunctions and failures |