Over the years, we've written a lot on the banning of incandescent (and now halogen) light bulbs for general service use. CFL bulbs never really caught on with consumers, but LEDs are more energy efficient than ever and can offer similar color rendering to incandescents.

But despite being "banned," the regular old 60 watt incandescent lamp is nearly as popular and available as ever, for those who know where to look.

This is because they're still used in traffic signal fixtures around the country. But these traffic signal bulbs have some significant differences.

Traffic Signal vs. General Service

The main differences between regular 60 watt incandescent bulbs and the type used in traffic signals relate to design, durability, and functionality. Here are the key points.

Design and Construction

Traffic signal bulbs are often built into a more rugged and durable casing to withstand harsh environmental conditions. They are exposed to more varied weather conditions, vibrations from wind and vehicle traffic, and exposure to the elements like rain or snow.

Traffic signal lamps are designed to operate in a way that manages heat more effectively because traffic signals can be exposed to high levels of sunlight and extreme temperatures, as well as sub-zero temperatures. The high heat generated by the lamp can prevent the fixtures from freezing over with ice in the winter.

(As an aside, LEDs also work great in cold temperatures, but they do not generate enough heat to melt snow and ice efficiently. Some manufacturers like GE produce LED traffic signals with separate heat units to overcome this limitation.)

These bulbs may have specific coatings or materials to create specific colors (red, yellow, green) with better light distribution, ensuring visibility from a long distance.

By contrast, regular general service bulbs have a standard construction with clear or frosted coatings suited for household use in more controlled environments. The filament and the bulb itself are designed for moderate heat dissipation and general illumination, without the need for high durability or efficient thermal management.

Durability and Longevity

Designed to have a much longer lifespan due to the need for continuous operation in a variety of weather conditions, traffic signal bulbs are built to handle constant use and often more extreme environments.

The filament is constructed to be more resistant to vibrations from traffic and external forces, making them more suitable for the constant movement of vehicles and adverse conditions. This also contributes to the longer expected life of traffic signal lamps, which may last 6,000-8,000 hours.

Standard incandescent bulbs have a much shorter lifespan compared to those used in traffic signals. They're typically designed for shorter usage periods, such as hours of use in a home or office, rather than constant 24/7 operation. They may last 1,000-2,500 hours at the most.

Power and Efficiency

Though they may also be 60 watts, the power used by traffic signal bulbs is often optimized for their specific function, ensuring they provide the right amount of brightness and visibility at different distances.

Traffic signal bulbs are often designed to be more energy efficient for long-term operation, but the technology used is meant for maximizing visibility rather than efficiency.

In fact, the Sylvania SuperSaver traffic signal bulbs (PDF brochure) are about 10% more efficient than standard incandescent, where a 54W bulb gives about the same lumen output as a 60W version that is not energy efficient. This is not nearly as efficient as switching to CFL or LED, but is adds up for municipalities utilizing incandescent traffic signal lamps.

Near the end of their production lives, incandescent bulbs also got more efficient in general, which includes the traffic signal bulbs and general service lights.

Regular incandescent bulbs are not optimized for long-term, high-visibility use. They were primarily focused on home lighting, so the energy efficiency was not as critical in the design (though there are energy-saving alternatives like LED bulbs now).

Cost

Due to their more rugged design, incandescent traffic signal lamps tend to be more expensive because of their specialized features, longevity, and environmental considerations. They are also often sold in bulk for municipal or commercial applications that may need dozens or thousands at a time.

Standard incandescent bulbs were cheaper and mass-produced for general use in homes and businesses. For many years, picking up pack of 6 or 12 bulbs was extremely inexpensive, until government efficiency standards did away with them almost completely.

Summary

Overall, the incandescent bulbs used in traffic signals are specifically engineered to withstand continuous use, provide visibility in different lighting and weather conditions, and have a longer lifespan.

Regular household incandescent bulbs, on the other hand, were designed primarily for indoor illumination and were not built to meet the demanding requirements of traffic management.