Roadway Lighting: From Candle to LED
Roadway Lighting: From Candle to LED
Can you imagine, that back before we even had vehicles, we had need to light the roadways? From the earliest civilizations, fire lit our way. As civilization came into the Preindustrial Era and moved onto the Modern Era, the way we have brought light to our path has drastically changed! Many people assume that the invention of the light bulb was the best thing to happen to lighting (Thanks Edison!!), and it definitely is one of the great inventions. Yet, as technology advances, LED, or light emitting diode, are revolutionizing the way we now light our world, and more importantly, how we light the roads we take.
Let’s go back for a moment, when candles and oils were the best source of light that we could find. The Greeks and the Romans began the use of what we call street lights. Above the heads of the citizens stood tall posts that contained a lantern, usually filled with an oil of some kind. This was done for the purpose to security; to light the path of a traveler or a wanderer, and deter possible thieves. At dusk, it was the responsibility of slaves to walk around the cities and light the lanterns. This method was utilized for thousands of years.
In the streets of Paris in the 16th century, following the invention of lanterns with glass windows, the quality of lighting was improved in, what was then called street lamps. It was the responsibility of the police officers in Paris to light these lanterns each evening at dusk. This was the reason that the police would change shifts at dusks. The officers would walk around lighting the city as their first task of their shift, while the early shift would finish their patrols. This overlap of the shifts at dusk is utilized even to this day by law enforcement officers.
Over 150 years before the invention of incandescent light bulbs, cities found the need for more practical lighting solutions than candles and lanterns with coal. In the early 1700’s gas lamp lighting systems began to be developed, and in 1807, Pall Mall, London was the first public streets to be lit by this gas lamp system. This system was widely used in Europe, and in 1813, the Westminster Bridge was lit with by gas. In 1816 Baltimore became the first US city to be illuminated with gas streetlights, and by the mid 1800’s kerosene was used primarily, as the safest fuel source for these lighting systems.
Only a couple of decades after they had perfected the gas lighting systems, arc lamps were invented. Originally known as an “Electric Candle,” these lamps where the first electric street lights. These were a carbon arc lamp using alternating current, consuming electrodes at an equal rate, providing consistent light.
Before the use of incandescent lighting solutions, arc lighting was the most popular method for lighting city streets. As metropoleis grew around the world, the major disadvantages of arc lighting became evident. Maintenance became an issue, as carbon electrodes would burn out quickly. The light the was emitted was intense. There was no way to filter the light, or have any variant in light output, known as lumens.
In the same year that Thomas Edison patented the incandescent light bulb, Cleveland, Ohio was the first US city to adapt an incandescent lighting system, second in the entire world. Incandescent lighting was used for street lights until the arrival of HIDs, or high-intensity discharge lamps. The popularity of this HID lighting system grew throughout the decades because the higher voltage in these circuits produced more light per watt consumed, making them more energy efficient than previous lighting systems. Before the invention of controls, a single switch or timing mechanism could be used to control all the lights in the entire area. Maintenance issues lessened, as transformers allowed a current to pass across the unit whether the bulb worked or not.
At that time, HID lighting seemed to solve most of the problems encountered over the centuries. However, advancement was inevitable. HPS, or high pressure sodium lamps, provided the best photopic illumination with the least consumption of energy. Both lights are efficient, and studies have shown that at equal light levels, HID provide the best illumination. Providing better peripheral vision at night; lowering accident rates, and increase pedestrian safety.
Never willing to settle, scientists have been working on the advancement of LED lighting, and their application in street lights. As LED technology continues to advance, photovoltaic-powered LED luminaires are gaining acceptance by municipalities and street departments, and city by city across the United States have been switching to these LED street lights.
LED luminaires used for street lights provide the ability to not only control when the light will illuminate, but also how bright of a light it will emit. These lights increase and decrease the intensity of the light based on the lunar light. Whether changes, full moon, or a light emitting event, like an outdoor concert, can all create a variance in the need for lighting. These features can make LED street lights the most energy-efficient, maintenance cost decrease, and overall increase in the quality of light.
Street lamps have made quite the transformation throughout the years. From candles, to coal and oil burning lamps, to gas, to arc lamps, to bulbs, and now on to LEDs: The future of lighting has yet to find the ultimate solution. The need for lighting our streets has been around for millennia, for keeping citizens safe. As technology advances, it is exciting to think were the future of lighting may take us.