Why are traditional streetlights being phased out?
Traditional streetlights primarily refer to high-pressure sodium (HPS) lamps, mercury lamps, and some metal-halide lamps. There are compelling reasons for phasing them out:
First, low energy efficiency: HPS lamps have a luminous efficacy of approximately 80–120 lm/W, and mercury lamps only 40–60 lm/W—far below the 150+ lm/W achieved by modern LEDs. This means traditional streetlights consume more electricity while producing less light.
Second, short lifespan: The average lifespan of an HPS bulb is 15,000–20,000 hours, and a mercury lamp's is about 10,000 hours, whereas LED streetlights can last 50,000–100,000 hours. Frequent bulb replacements result in high maintenance costs and traffic disruptions.
Third, poor light quality: HPS lamps emit an orange-yellow light (color temperature around 1900K–2100K) with a very low Color Rendering Index (CRI ≈ 20), causing severe color distortion. During night driving, it is difficult for drivers to distinguish oil stains, puddles, or the color of pedestrians' clothing, posing safety risks.
Fourth, slow startup: HPS lamps require a 3–10 minute warm-up period to reach full brightness and cannot be illuminated instantly; if power is interrupted, they must cool down before restarting, which is extremely inconvenient.
Fifth, presence of hazardous substances: Both HPS and mercury lamps contain mercury; breakage causes environmental pollution, and disposal requires special handling.
Sixth, difficulty in dimming: Dimming traditional streetlights requires expensive dimmable ballasts, and the dimming process significantly shortens bulb lifespan. Consequently, most cities cannot implement power reduction for energy savings during the late-night hours.
Seventh, hazardous maintenance: Frequent bulb replacement requires aerial work platforms, increasing the risk of electric shock and falls for workers.
Given these drawbacks, over 100 countries and regions worldwide have established timetables to phase out inefficient streetlights. China is also promoting the replacement of traditional streetlights with LED versions through its "Urban Lighting Energy-Saving Retrofit" program.
