By Paul Abelson
Industry experts have long understood that attributes of light-emitting diodes (LEDs) would hold great potential for the future of trucking. In fact, two decades ago, the Truck Writers of North America paid heed to Grote Industries for introducing LED clearance/ marker lights. (See grey text.)
At the 2011 Mid-America Trucking Show, the Truck Writers of North America awarded the Grote Trophy for the 20th time. The annual award honors technical achievement in design and development of commercial vehicles and their maintenance. It was first awarded to Grote Industries for introducing light-emitting diode (LED) clearance/marker lights. Since then, Grote has endowed the award and added subsequent winners' names to the original trophy.
Although early LED models initially cost as much as 20 times the bulb assemblies they replaced, they were virtually indestructible, offering the promise of huge savings over the life of a truck. Their primary advantages are long life and low current draw — the benefits that make them a popular choice for safety lighting.
Early LED stop/turn/tail (STT) lamps needed as many as 96 diodes to meet DOT brightness requirements. By 2009, Truck-Lite had developed a single-diode STT lamp that did the job. Since they don't look like today's typical six-to ten-diode LED lamps, they are less prone to theft and still popular with some fleets.
LED technology has had a significant impact on maintenance budgets and helped fleet managers meet standards such as the Federal Motor Carrier Safety Administration's FMVSS108, which specifies minimum safety lighting required for a truck, and 49 CFR 393.11 in the Code of Federal Regulations, requiring all lamps to be in operable condition.
Twenty years ago, surveys of maintenance costs done by The Maintenance Council of the American Trucking Associations indicated that lighting represented the highest maintenance expense for fleets. That included parts and labor, fines for violations, and workers' compensation claims for falls from ladders while changing upper clearance/ marker lamps. Today, lamp maintenance doesn't even make the top 20 list.
Converting to LEDs also saves fuel. That's why automobile manufacturers, faced with increasingly stringent fuel-economy requirements, are turning to LEDs for interior and safety lighting. Newer luxury vehicles and hybrids alike use them, and they are either standard or available on all commercial vehicles.
Traditional lamps generate heat (see sidebar, next page), but the heat energy is wasted. This relates directly to fuel consumption — the hotter a light source gets, the more fuel is wasted. LEDs draw less current and remain cool, resulting in better mileage.
Since the current draw is low, operators can specify smaller, lighter alternators. Even standard alternators tend to last longer while operating under less of a load. Lower current consumption also translates to longer work time in hybrid trucks.
This cooler operation caused the U.S. Army to investigate LED headlights. A low heat signature is invaluable when an enemy is using heat-seeking missiles. Truck-Lite developed a 7-inch round LED configuration that fits in a standard headlamp mounting. It is now being used in several military vehicles, including M-ATV and other mine-resistant ambush-protected vehicles, heavy expanded mobility tactical trucks, and HMWWVs — better known as Humvees.
Because the Army, Marines, and Air Force have purchased tens of thousands, LED prices in the civilian market have dropped significantly. We are now at the point where specifying these headlamps could be cost-effective for many long-life civilian applications. Truck-Lite is now developing designs for trucks with aerodynamic headlight assemblies.
For work truck auxiliary lighting, LEDs are growing in popularity. But in addition to just flood- and spotlights, the lamps can be tailored to provide various patterns of coverage. All lighting manufacturers now have LED work lights in their catalogs.
While LED headlamps may be a few years away from being practical for all, safety lighting and work lamps are well established. If your fleet hasn't made the switch, what are you waiting for?
— Paul Abelson (firstname.lastname@example.org) is a former director of the Technology and Maintenance Council (TMC) of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.
WHAT'S THE DIFFERENCE?
Traditional headlights vs. LEDs
Traditional lamps use incandescent bulbs and reflectors. The bulbs have filaments that heat up to glow bright white. Their color is determined by their lens, which filters out colors other than the one needed. The heated filaments are weak and susceptible to breakage.
LEDs create light by emitting photons directly when electric current passes through them. By altering the surface composition of the diode, it can be tailored to emit a very narrow range of color frequencies, yielding an almost pure color. In fact, a red LED seen through another color lens will still look red. The same holds true for any other color diode but white.
White LEDs emit a broad spectrum of frequencies. Arrayed in specific patterns with purpose-designed reflectors, they can be tailored for a variety of tasks.