By Daniel Stern, DVN General Editor
Last week, we reported on the IIHS tests that ranked most headlamps poor or marginal. In an online video, a senior IIHS researcher explains a bit about the tests and some of the results. The IIHS headlamp test and rating protocol and its rationale have been made available in full. This week, we take a more detailed look at the tests and their implications.
IIHS' decision to test headlamps as received on the vehicle, rather than aiming them to an applicable nominally correct setting, is defensible; most North Americans never think about their headlamp aim, and most North American jurisdictions do not periodically inspect vehicle lights (or inspect to a standard so lax as to be meaningless, wherein low beams aimed anywhere from 0.76° above to 0.76° below H-H are considered acceptably aimed). Clearly, factory new-vehicle aim has a crucial influence on results in the IIHS headlamp scrutiny. So on a new vehicle in North America, where are the headlamps generally aimed? Here is a chart put together by IIHS of aim angles measured on a variety of new 2015 cars: the Honda Civic, Honda Accord, Jeep Patriot, Jeep Cherokee, Subaru Forester, Toyota Prius V, and Ford F150, in that order on the horizontal axis. The vertical axis runs from 0.6° Down to 0.6° Up. Left headlamps are in blue; right lamps in orange. Despite most of these vehicles having VOR-type low beams meant to be aimed straight ahead (0°), most of the tested vehicles had headlamps aimed from 0.1° down to more than 0.5° down. The Jeep Cherokee, on the other hand, had lamps aimed almost 0.4° up.
And here is a plot of the aim of VOR-type low beams on the midsize cars IIHS tested for this present round of tests. Nominal aim is 0.0°, but the measured aim ranged quite far from there in both directions: