In the 1960s, federal regulations in the United States required uniform headlights on all cars, but this rule was lifted in 1983 to allow car manufacturers to create different headlights that matched the design of their automobiles, while still meeting federal standards.
Today's automotive headlights vary greatly in terms of their shape, brightness, height and distance of their beams. While headlights are tested by the federal government in a laboratory setting, lights are not tested or inspected once a consumer owns a car. Many states require that headlights must illuminate 115 feet, but this is seldom tested for.
A digital light meter is a scientific measuring device that you can use to measure the brightness of your car's headlights. When measuring the brightness of headlights, you should do so at night in an area with little or no illumination. If testing against another vehicle, make sure to stand the same distance from each set of headlights and to aim the meter at the center of the beam.
You don't need a light meter to do a simple road test. Following a fatal accident, a news crew in Massachusetts tested a variety of cars to see if they were able to illuminate 115 feet in front of the vehicle. You can set up your own test in an empty parking lot or closed off road by placing an object 115 feet away from a car and seeing if you can see the object when seated in the driver's seat of the car with the headlights on.
