As street lighting is reinvented through modern outdoor LED lighting technology, the industry should also re-evaluate the performance indicators used to compare street lighting technologies.
Purchasers of LED products, including those for outdoor lighting, often request that LED manufacturers provide direct lighting replacements based on existing street light output rather than the actual performance at the road surface. This approach can inhibit customers from accurately comparing the savings possible through the implementation of LED Street Lights.
A common mistake is to make a direct lumen comparison when specifying retrofits. The comparison of lumens provided by typical HID lighting and LED Street lighting technologies is often inaccurate, due to the enhanced individual aiming and distribution capabilities of street LED lighting. With Street LED light technology, lumens are precisely controlled to minimize over-lighting or hot spots, and ensure sufficient lighting throughout the intended distribution area. Light waste is also minimized or eliminated, often without the use of external shielding.
Therefore, when evaluating performance at the road surface, illuminate (foot-candles delivered to the road surface) or luminescence (candela/square meter reflected from the road surface) should be used to determine the quality of a roadway LED lighting design.
Photo metric applications or layouts can also be performed to make sure the street light levels meet requirements.