As part of our comprehensive auto-testing program, Consumer Reports evaluates headlight performance by using a combination of lab measurements and outdoor testing. 

The first step is to align the lights using a computerized laser system in a dedicated indoor lab. Not unlike checking the aim of headlights against a garage door, our advanced system uses computer software and lasers to assist our technicians in placing the headlights precisely at the middle of their allowable alignment range.

Indoor assessments also include an evaluation of how much stray light shines above the headlights, which can illuminate precipitation when weather is poor. The windowless building that serves as the lab was designed for testing headlights, and it is equipped with a lift and a specialized screen to place the lights at their nominal position before testing.

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We then move outdoors to test headlights at our track on a dark, moonless night. Our headlight specialists set up a series of black targets at prescribed intervals and widths along an almost 1,000-foot-long level section of track (shown below). They then look at low- and high-beam performance, evaluating reach, intensity, width, and the evenness of the light pattern.

Straight-ahead illumination is most important because it determines how much time and distance the headlights allow a driver to see, react, and brake for pedestrians, animals, or objects in the road. Our specialists also note glare effects—whether the lights would be discomforting to an oncoming driver. And they determine whether the transition, or cutoff, of light at the top of the low-beam pattern is so sharp it reduces the headlight's range as the car moves over curves, dips, and uneven roads or contributes to oncoming glare.

Headlight testing is just one of the more than 50 tests we perform on each car we buy.

Setting up to test headlights at the CR Auto Test Center.
Setting up to test headlights at the CR Auto Test Center.