NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

Which HID lamp is commonly used for street lighting?

1. Metal Halide

2. High-pressure sodium

3. Incandescent

4. Fluorescent

The correct answer is: High-pressure sodium

High-pressure sodium (HPS) lamps are commonly used for street lighting due to several advantageous properties. One of the primary reasons for their widespread use is their efficiency in converting electrical energy into visible light. HPS lamps produce a significant amount of light output while consuming relatively low amounts of electricity compared to other types of lamps. Additionally, HPS lamps have a long lifespan, often exceeding 24,000 hours, which reduces the frequency and cost of replacements. They emit a yellow-orange light that penetrates fog and rain better than many other colors of light, improving visibility for drivers and pedestrians at night. This color temperature is typically perceived as less attractive, which also serves as a deterrent for potential criminal activity in poorly lit areas. Metal halide lamps, while also used in some outdoor applications, do not have the same efficiency or lifespan as HPS lamps, making them less favorable for street lighting. Incandescent and fluorescent lamps are rarely used for street lighting due to their shorter lifespans and lower energy efficiency, as well as their inability to provide the necessary illumination levels required for safe street lighting.