Everything You Need to Know About Driving Lights
There's so much more to seeing through the dark than brightness alone
Outside's long reads email newsletter features our strongest writing, most ambitious reporting, and award-winning storytelling about the outdoors. Sign up today.
Your car or truck’s stock headlights may be adequate on paved roads at moderate speeds, especially when paired with streetlights. But throw in the utter darkness in the middle of nowhere, or even just a little weather, and you’ll find them sorely lacking. What can you do about that? Fit your vehicle with aftermarket driving lights.
Aren’t Those Things Illegal?
Regulations vary by state, but running non-DOT-approved lights on both paved and dirt roads is illegal everywhere in the United States. In some states, simply driving around with them uncovered, even if they’re not switched on, is against the law, too, so be sure to check your own state’s regulations. However, aftermarket driving lights, regardless of their certifications, are legal on off-road trails and in other countries like Australia, where the transportation mix leans more rural. If you do outfit your car with them, switch them on when you need them, and be careful to turn them off any time you’re near other drivers.
“Car shoppers need to think about headlights as a safety feature in the same way they think about brakes or even seat belts,” stated Jennifer Stockburger, director of operations at Consumer Reports’ vehicle test center, in a test of standard vehicle headlights that the publication ran last year. So why not make those lights better?
(Andrew Collins, over at the car website Jalopnik, put together a great explanation of why LED bulb upgrades for your standard headlamps don’t work.)
After appropriate tires, driving lights may prove to be the most effective safety aid you can add: being able to see farther down the road increases the amount of time you have to react to obstacles. That’s especially important in slippery conditions, where braking distances increase. Slippery conditions are caused by precipitation, which some driving lights may also help you see through.
I think driving lights are so helpful that they were among the first modifications I made on all three of the trucks my wife and I drive. And because anything worth doing is worth doing right, I went to great lengths to ensure each of those trucks is fitted with the best possible solution for its individual use case. Here’s everything I learned in the process.
Outright Power Is Meaningless
A typical 18-wheeler has about 600 horsepower. A Tesla Model 3 has 258 horsepower. Which one is faster?
In the same way that horsepower alone cannot determine a vehicle’s performance, the stated power of a driving light is meaningless without context. In the past, the power of a driving light was stated in watts. This is a fairly useless way of looking at light performance, because it’s only a measure of the power used. With the advent of the first high-intensity-discharge (HID) bulbs and then light-emitting diodes (LED), lighting technology became drastically more efficient than the halogen bulbs of yore. A light made using one of those technologies will produce far more power than a halogen headlamp with equivalent draw. So light makers began quoting power in lumens.
A lumen is a standard unit of brightness, the amount of brightness a light produces in all directions. Because it’s an output number, it’s loosely equivalent to that horsepower comparison we’re using. But raw lumens are just like horsepower in another way—they’re a calculation, not a measurement.
The makers of driving lights don’t manufacture bulbs or LEDs themselves, they buy them from a handful of suppliers, then assemble them into the driving lights you buy using reflectors, lenses, circuit boards, mounts, and other parts. Those bulb or LED manufacturers supply the light makers with performance figures, and it’s common to see those figures simply passed along to the consumer. If a lighting brand assembles a driving light equipped with ten LEDs that the maker claims are capable of up to 1,000 lumens each, then that’s a 10,000-lumen driving light, right? Not so fast.
If you ever see light output quoted in “raw” lumens, you should understand that number to be entirely fictional. Even if a lightbulb or LED is theoretically capable of producing 1,000 lumens in ideal lab conditions, its power will typically be reduced 10 to 25 percent when installed in a light due to losses from heat, reflections off the inside of the lens, or simply quality variances.
A more realistic determination of light output is effective lumens, which is actually a measurement taken 3.3 feet in front of the light. Even in a best-case scenario, that 1,000-raw-lumens LED is really only going to be capable of producing 750 to 900 effective lumens. And there are an awful lot of driving lights out there that are very far from being a best-case scenario.
Plus, measuring only the outright amount of lumens a light puts out remains an unrealistic way to express the performance of that light—mostly because you’re not using a driving light to illuminate something sitting 3.3 feet in front of it. You’re using a driving light to try and see stuff farther down the road or trail than your stock headlights reach. So to determine the effectiveness of a driving light, you need to know how much of its light reaches a certain distance. Enter lux, which is a measurement of the intensity of light.
You’ll typically find lux expressed as the distance at which a light can project one of them. One lux is equivalent to one lumen per 10.8 square feet. Think of that as the minimum amount of light it takes to comfortably read normal book-size text. Because that’s an amount of light it’s easy to envision, this measurement makes it simple to understand the performance of a given light source or to compare them. If one driving light is capable of producing one lux at 600 yards, and another can do the same at 800 yards, we can all understand that the latter is the more powerful driving light and will enable us to see farther down the road.
Because lux must be expensively tested in the real world, rather than simply quoted from lab results, I’ve noticed that only higher-end light manufacturers tend to report this number. The best of those submit their lights to an independent third-party tester to give their customers total transparency.
LEDs Versus HIDs
You’ll note that a lot of the talk above centers around the performance of LEDs. That’s because the technology is so trendy right now that it dominates the driving-light space. And that’s a shame, because while there are things LEDs can do that HIDs cannot, both remain very relevant to today’s drivers.
“Yes, they’re stylish, but drivers need lights that will make them safer and not just make a fashion statement,” explains Consumer Reports’ Stockburger, who says that the small size and low power draw of LEDs are allowing designers to package them into new shapes and spaces and that light makers are embracing them for one important reason beyond style, too: they’re cheap.
A light-emitting diode is a small semiconductor that emits light when electrical current passes through it. Because it’s entirely electric, it reaches full intensity the moment it’s powered on. Inside an HID bulb, pressurized xenon gas is excited by the current passing between two electrodes. Because it takes a couple of seconds for that gas to heat up, HIDs, especially very powerful ones, take a couple of seconds to reach full intensity. Hit the switch for an LED light and it will light up instantaneously; in contrast, HIDs grow in brightness for several seconds after being turned on.
The life span of an LED is typically 50,000 hours. The life span of an HID bulb is around 9,000 hours. The former will easily outlast any vehicle it’s mounted to. The latter is equivalent to roughly 90,000 miles of use. But since you likely don’t drive exclusively at night, or exclusively on remote tracks with no other drivers, HID bulbs will likely outlast your vehicle, too. And while LEDs may have a longer life span, if an LED in a driving light fails, you’ll probably need to replace the entire light. If an HID bulb burns out, you can simply replace the bulb.
LEDs are small, and it takes several to many of them to produce a powerful driving light. That makes it challenging to design and produce lenses and reflectors for each LED that are capable of gathering and throwing light over a long distance. HIDs are so powerful that it only takes one to make an effective driving light, meaning that only a single lens and reflector is needed. This is easier and cheaper for the light maker, allowing many brands to sell lights capable of reaching an extraordinary distance at a reasonable price.
It’s a common misconception that LEDs don’t produce heat. More accurately, LEDs don’t produce infrared radiation; they don’t project heat from the light source like incandescent bulbs do. But they do produce heat at their semiconductor junctions, sometimes converting as much as 85 percent of input energy into heat and just 15 percent into visible light. Managing this heat is a major challenge for designers of driving lights, and it’s why they’re typically housed in cast-aluminum heat sinks. In contrast, HIDs do produce infrared radiation (heat) in addition to visible light. The lens of an HID driving light will feel warm, but its housing will feel cool.
These factors add up to some different packaging requirements for HIDs and LEDs. HID bulbs are a couple inches long and must be fitted with a ballast (which temporarily boosts input power when the light is turned on to arc electricity between the electrodes) and housed in a reflector to work properly. An HID driving light will typically melt airborne snow and ice before it can accumulate on the lens. While high-power LEDs require heat sinks, low-power ones do not. And if projecting their light over distance is not a concern, neither do they require any sort of reflector or lens, just a protective housing. So lower-power LEDs can be packaged into very small lights. Airborne snow and ice can accumulate on the lenses of LED driving lights.
The color of light is expressed as a temperature, ranging from warm to cool. Warm light—red to yellow—penetrates dust, fog, and precipitation with minimal reflection, thanks to its long wavelengths, but it can impair the ability of our eyes to discern color. Cool light—blue to violet—can appear very bright, but it produces glare and reflections due to its short wavelengths and can cause eye strain. What you want is something as close to natural daylight as possible, which will be easiest on our eyes, provide ample illumination, good contrast, and accurate color rendering. While it’s common to see both HID and LED lights lean toward the cool side of the spectrum, that’s just because most light makers don’t take the time to dial in accurate color rendering.
The color temperature of daylight varies with conditions but is commonly understood to range from 5,000 to 6,500 kelvin. Driving lights operating in this temperature range will not appear yellow or blue in color but rather a nice, even white. Driving with lights that operate in this range (or slightly warmer) will maximize vision, contrast, and depth perception, all while reducing eye fatigue.
Outright straight-line distance in front of your vehicle probably isn’t the only area you want your driving lights to illuminate. Depending on the terrain you’re driving through, and the weather conditions, it may be optimal to light up an area closer to the front of your vehicle, more to its sides, or, if you’re really working hard off-road or just camping, maybe to the rear as well.
By helping you see into the distance, which maximizes your reaction time, spotlights are most helpful at higher speeds. Illuminating a mile out really enables you to relax on long nighttime drives, rather than straining your eyes to make out the presence of animals, ditches, or other obstacles at the last second. But high-power spotlights can also overwhelm you at lower speeds, particularly in technical terrain, which may reflect light back to you at close distance.
Floodlights illuminate a broader area out to a shorter distance—typically a couple hundred yards. In doing so, they can help you see potential hazards off to the side of the road or trail and help light up turns and corners. You don’t want floodlights to be too terribly bright, since they’re designed to work at distances closer to your eyes. Floodlights may be packaged into an all-round lighting solution, like a light bar, or may come designed for a specific zone, like a fog light. By upgrading the power of fog lights, running them in a warm color temperature, and angling them down and out to the sides, you can maximize their ability to provide vision through fog or dust. Some people also mount small floodlights on the sides of their trucks, pointing perpendicularly to the direction of travel. These may help you navigate very challenging terrain or just illuminate the entire area surrounding the truck when you come to a stop.
Work lights are designed to give you good vision inside the bed of a pickup or to the rear of any vehicle. They don’t help with driving, but rather make effecting roadside repairs or setting up camp as easy as possible.
A vehicle can be fitted with any or all of the above. Switched separately, different lighting solutions illuminating different zones can help you respond to changing driving conditions, variable weather, or just the variety of tasks your vehicle may help you perform.
My wife and I have three trucks, all designed for different tasks. The lights fitted to each reflect their specific use cases.
The first is our 1998 Toyota 4Runner (above), which I built for us to use when Montana’s winter weather gets particularly bad and the likelihood of damaging a vehicle is high. It’s also the car we loan to houseguests; one of them drove it to Salt Lake City and back over the weekend.
The 4Runner is fitted with a pair of six-inch ARB AR-21 driving lights. With a pair of round lights, it’s typical to fit one designed for flood and one designed for spot, in order to add the benefits of both to your vehicle. But because the old 4Runner is mostly used to drive around our local area, typically in snow or off-road, and rarely sees highway speeds, I instead opted for two flood-pattern lights. These produce a very wide spread of illumination, maximizing the amount of information its driver is given about the surfaces they’re driving on. But they still throw one lux at 1820 feet, which translates to one-third mile of usable light. That gives its driver 19 seconds of reaction time at 65 miles per hour.
And because the 4Runner is our blizzard truck, I fitted a set of amber covers to those AR-21’s. The longer wavelength of yellow light refracts less off airborne snow and other precipitation, allowing us to see through it to a much greater degree. The trade-off is that, with flatter color rendering, the amber lights are not good at helping distinguish the brown hide of a deer, elk, or other animals from a black road or green woods. So those amber filters come off for summer driving.
My 2019 Ford Ranger is our adventure vehicle. Its build prioritizes practicality off-road and in camp at the expense of convenience around town and refinement on long highway drives. Still, it’s seen the most use, carrying us and our dogs to southern Baja, Mexico, for our wedding, taking us on daily hikes, and getting us to weekend adventures around southwest Montana. It also supports my hunting, which, as you know if you participate in that sport, takes place in the absolute worst weather possible.
The biggest risk to drivers down in Baja is all the livestock that wanders around the roads at night. There are no streetlamps on the peninsula’s rural roads, and cows, horses, and other animals roam freely across them. Up here in Montana, we have everything from elk to moose to grizzlies on the roads, too. So I wanted this truck to have a lot of light and be able to respond to varying weather conditions with different kinds of light.
I initially tried to do that with one of the well-regarded American driving-light brands, which is when I learned that raw lumens don’t necessarily translate to real-world light performance. Frustrated, I looked for a better solution, and that’s when I discovered Lightforce. Little known in this country, the Australian brand manufacturers all its products in Australia and submits every one of its lights to an independent body for performance testing. Lightforce takes special care to ensure its driving lights operate at 5,000 kelvin, which should be considered an ideal color temperature. It’s warm enough to see through dust and precipitation, yet accurately renders colors, and is relaxing to look at.
With the Ranger, I wanted to achieve floodlighting across the road in front of me and long-distance performance for higher speeds in places like Baja or remote parts of Montana. I also wanted short-distance amber fog lights for driving in heavy snow or fog and practical work lights for the GoFastCampers Platform that rides in the truck’s bed. I achieved all of that by mounting a 30-inch single-row Lightforce bar in the front bumper, a 40-inch two-row bar on the roof, and some affordable new camper lights from TruckParts.Parts on the GoFastCampers Platform. I’ve struggled to find fog lights capable of producing enough power to make them worthwhile, but I just received a pair of KC Flex Era 3’s and plan to wire those up later this month. Fingers crossed.
The 30-inch bar in the bumper is capable of achieving one lux at 1970 feet, but I have it angled downward enough that it cuts off at about 1,000 feet . This arrangement creates a very bright flood pattern in front of the truck, out to a distance that’s ideal for navigating slippery surfaces off-road or in winter conditions. Pointed at the horizon, the 40-inch two-row bar on the roof provides one lux of illumination at 2,800 feet. The LEDs in both bars are arranged in a combination pattern, pivoting from pointing very far outward at the sides to straight ahead in the middle. With both switched on, that effectively means I’m turning a semicircle with a radius of half a mile into daylight. That capability is empowering, giving me the most information possible with which to navigate complicated trail junctions or pick the best lines over or around challenging obstacles. At 65 mph, these lights give me 29 seconds of reaction time.
The TruckParts.Parts work lights in the camper run off the battery connected to my solar panels and are wired to a switch just inside the tailgate. Inexpensively manufactured, I’d hesitate to quote any performance figures for them, but they’re bright enough to illuminate the entire bed of the truck, and because the side lights mount inside the GoFastCamper’s lift panels, they’ll light up a reasonably large campsite, too. They switch from white to red (which attracts fewer bugs) and are capable of dimming.
But bolting ungainly light bars and light pods all over the front of a truck isn’t exactly an aerodynamic or visually appealing solution. So for my wife’s Land Cruiser, which I’m in the process of building into a peerlessly capable luxury travel vehicle, I wanted to find a sleeker alternative that didn’t sacrifice performance. I ended up finding something that provides substantially more light than what’s fitted to the Ranger, all in an elegant pair of driving lights that perfectly compliment the Toyota’s styling.
By wrapping the perimeter of a large HID reflector with a ring of 20 LEDs, Lightforce has created in its new HTX2 not only one of the most powerful driving lights ever made but also one of the most versatile. Together, a pair of HTX2’s provides one lux of light at 1.1 miles, with a beam that’s 122 yards wide. The HID and LED components switch separately, so you can run either—or both—depending on your needs. And that makes this a true two-light solution, not just for any driving-light needs but for lights which outperform anything else out there.
Key to that performance is how well integrated and complimentary the light provided by both elements is. The color temperature of the light produced by both the HID and LED is perfectly matched (both are 5,000 kelvin), and the meticulous design of the individual reflectors has resulted in no shadows, artifacts, or perimeters visible within the projected light.
You’ll notice that, right from the beginning of the article, I’ve talked about seeing through the dark, rather than just illuminating it. Switch on most powerful LED driving lights, and you’ll be overwhelmed—not by how much light they produce but by the glare and reflections created by that light. Not so on the HTX2’s. The perimeter LEDs alone provide substantially more illumination than the AR-21’s on the 4Runner. Add the HIDs, and it’s like a tunnel has been bored in the night in front of you. There’s no glare, and reflections only become an issue with close-distance road signs. The difference between these things and other driving lights is like the difference between cheap and expensive binoculars.
Why does anyone need such powerful lights? Here in Montana, where the population density is six people per square mile, the nighttime speed limit on rural and dirt roads just so happens to be 65 mph. At that speed, the Lightforce HTX2’s give my wife 61 seconds with which to spot something dangerous, make a plan to avoid it, then execute that plan. We use these things because they provide the most safety possible. They really do enable us to see through the dark.