Survey of the Current State of Vehicle Headlamp Aim

A study of vehicle headlamp vertical aim was undertaken to determine the extent to which mis-aim exists in a sample of American-owned vehicles. In addition to headlamp aim measurement, additional information (e.g., age, physical condition, vehicle type, source type, and optical design) was collected for more than 120 vehicles representing in-use and new vehicles. On average, headlamps for currently registered vehicles were aimed slightly downward, and for new vehicles were aimed close to the nominally correct alignment. However, 60% of currently registered vehicles had at least one headlamp aimed outside the tolerances allowed by the standards of the Society of Automotive Engineers, consistent with the results of previous studies. Approximately 45% of the new vehicles measured had at least one headlamp mis-aimed. There were not any statistically reliable relationships between vertical mis-aim and vehicle age, vehicle type, headlamp optical systems or headlamp source (i.e., halogen versus high intensity discharge). Based on the samples measured, it would be relatively common to find headlamps that produce high light levels above a horizontal plane containing the light source in the headlamps due to mis-aim. Proper aim of headlamps would probably reduce the likelihood of headlamp glare and improve driver visibility on American-owned vehicles.