In the case of HID headlamps, that translates into a larger and deeper field of vision for the driver; the more you see ahead of you at night, the safer you’ll be. It also reduces the driver’s eye strain, hence reducing fatigue and keeping the driver more alert and aware.
“The sleep cycle of a human being is defined by the melatonin secretions in the brain,” Dassanayake explains. “In literature, people have found that certain wavelengths of light help better secretion of melatonin, and it keeps (drivers) awake and alert... and helps keep their attention and reduce their fatigue.
“Fatigue comes from the amount of work you have to do to be in control and be aware; in other words, it’s tied to the cognitive loading that someone has to go through,” he says. “So, the visible input is one aspect of that cognitive loading. The visible aspect can be impacted by proper lighting with the correct spectral content.”
Indeed, a study conducted on German drivers by TÜVRheinland®Group, a global compliance and testing company, finds that the number of new cars in Germany with HID lighting has been increasing dramatically, and suggests that there may have been up to 18 percent fewer fatalities on German roads as a result of the increased use of Xenon (HID) car lighting. The study also finds that up to 1,200 road fatalities in Germany could be avoided every year if all cars had Xenon lighting.
“You get a lot more light down the road in a wider beam pattern with HID, so he’s able to see more area,” says Ryan. “Then there’s also color temperature: HID is perceived as a whiter light, and it more closely resembles daylight than its halogen counterparts. So, it’s more natural for the eyes to see in this environment, there’s less strain on the eyes, which can result in less fatigue for the driver.”
The safety factor extends to the rear of the vehicle as well. Cars and trucks equipped with LED brake lights have a clear safety advantage over vehicles with incandescent brake lamps.
“Tail lamps with LEDs come on very fast, (in) twelve nanoseconds; for halogen or incandescent it’s about 200 milliseconds,” Dassanayake says. “So, with LED it comes on immediately... and that instantaneous change triggers your direct view and your peripheral view. If you’re driving at about 60 mph, it’s a good nine or 10-foot advantage.”
So far, LED headlamps have barely registered in the marketplace, but that may soon be changing, according to GM’s Larsen.
“Lexus now has an LED headlamp, and we’ve announced that we’re going to have an LED headlamp on the Escalade by the end of this year,” he explains.
“The LED headlights have a few things going for them,” he says. “One is styling; our stylists always want to set our vehicles apart, and LEDs give you that opportunity. The second benefit is that very soon, within the next couple years, power consumption of LED headlamps is going to be the same as or lower than halogen (55 watts) or even HID (35 watts). LEDs could be down to 25, 20, maybe even 15 watts, and with fuel prices the way they are in America, that’s becoming a big issue, as LEDs may be a big fuel-saver.”
LED headlights also take the “quality of light” issue a quantum leap ahead of HID headlights, which are already pretty good.
HID headlights already put out more light, and a whiter light, than halogen bulbs, Larsen explains, “So you get that perceived benefit of a lot more light.”
The step up from HID to LED headlights will offer that same perceived benefit, in spades. “LED headlights will offer performance equivalent to an HID, but the light from an LED headlamp is going to be a lot whiter, more like sunlight,” Larsen says. “So, your perception of the light output when you go to LED is that it’s even more light than an HID, even though it’s the same.”
PROS & CONS
Of course, as with any maturing technology, it’s not all sunshine and roses; LED and HID lights have their own maintenance issues.
“The one drawback of an LED lamp is that if it does burn out, you’ve got to replace the whole thing,” Larsen says. “They’re not serviceable; there are actually legal requirements about serviceability of LEDs and what you can and can’t do. So, if your LED stop lamp goes out, you have to replace the unit.”
Lessons in LED