The Insurance Institute for Highway Safety (IIHS) has begun testing headlights and including those results in its overall safety ratings. The first group of vehicles to be tested were midsize cars. The results were pretty disparaging.
The ratings are widely respected by the industry and consumers. They are based on Passive Safety – how well a vehicle protects occupants in a crash and Active Safety – features that help prevent a crash or lessen its severity. The IIHS is now including headlight tests in the ratings.
Headlight tests are conducted as the vehicle travels straight ahead and on curves. Sensors measure how far the light travels “with an intensity of at least 5 lux”. Lux is a unit that measure illuminates or how much light falls on a surface. IIHS says for comparison purposes, a full moon on clear night illuminates the ground to about one lux.
Headlights tested under five conditions
Both high and low beams are measured under five situations – straight, full left and right and sharp full left and right turns. Glare to oncoming vehicles from low beams is also measured and factored into the rating.
The majority of headlights use one of three different light sources: halogen, high-intensity discharge (HID) or LED. Each system is paired with either reflectors or projector lenses. Reflectors bounce the light forward from multiple surfaces. Projectors use a single lens to broadcast the light forward. Most of the good- and acceptable-rated headlight systems have HID -sourced light and projector lenses. The IIHS points out “having HIDs and/or projector lenses doesn’t guarantee good or acceptable performance”.
Adding further confusion and difficulty for consumers, is the fact headlight systems for the same vehicle can vary according to trim level. For example, within the 31 mid-size cars tested, there were 44 possible headlight configurations!
Best available headlights on 11 cars rated only “acceptable”.
The Toyota Prius V was the only one of thirty-one 2016 model year mid-size cars tested by the IIHS to receive a “good” rating. The IIHS says the Prius V’s LED low beams give someone driving at 110 k/hr. in a straight line, sufficient time to identify an obstacle on the right side of the road, and brake to a stop. Someone with halogen lights would have to be travelling at less than 80 k/hr. to avoid hitting that object.
The best available headlights on 11 of the mid-size cars tested received an “acceptable” rating. Nine were judged “marginal” and 10 could not be purchased with anything other than “poor”-rated headlights.
Obviously price is not a factor. The Prius received the highest rating and the BMW 3 Series with halogen headlights the lowest. A driver in that car would have to going less than 57 k/hr. to avoid an incident. A higher trim level of the same BMW equipped with LED curve-adapting lights with high beam assist received a higher “marginal” rating.
The IIHS says systems that turn to illuminate around a corner do not necessarily get a better rating. It gave a “poor” rating to the Cadillac ATS, Kia Optima and Mercedes-Benz C-Class,. All were equipped with adaptive low and high beams. Glare was the problem with the Kia. The IIHS says the adaptive system provides better visibility than non-adaptive systems, but excessive glare for oncoming vehicles.
Another example of how different systems on the same car can show different results is the Honda Accord. The base halogen system received an acceptable rating, while an available LED system with high-beam assist earned only a “marginal” rating.
IIHS ratings – 2016 midsize cars
Best available headlight system for each model
Toyota Prius V
Honda Accord 4-door
(built after Nov. 2015)
BMW 2 series
BMW 3 series
Chevrolet Malibu Limited