The basic mechanics of how LEDs create light are very different than that of incandescent lights used in traditional traffic signal operations. As described below, efficiency can be measured by the amount of useable energy.
Efficiency of Incandescent Lights
A standard light bulb relies upon electrically heating an element to emit visible light. Light emission requires a significant amount of power to occur. This process is called incandescence. Approximately 2% of the emitted energy from an incandescent source is useable visible light with the remaining 98% being wasted heat. Incandescent bulbs are likely to burn out frequently and require replacement each year.
Efficiency of LED Lights
In contrast, LEDs are much more efficient and last longer. That’s because LEDs emit light by using an electrical current to create a bond between positive and negative charges. This process is called electroluminescence. This is much more efficient, as nearly 100% of the emitted energy from an LED source is useable visible light. Due to varying energy use, LED traffic lights are known to last approximately 10 times longer than incandescent traffic lights. LED traffic lights usually have a replacement warranty of 5 years, but are expected to last longer.
Diffused vs. Direct Light
Standard incandescent light is diffused light, which basically means the light spreads out when in operation. Standard LEDs produce direct light but can be manipulated to diffuse, or spread out, so the light is visible at different angles. This can be controlled by altering the size, shape and location of some of the LED components that make up an LED traffic light.