Recently there has been a considerable amount of interest in formally adopting visual aiming for headlamps in the United States. Because of this interest, several studies have been made of how the sharpness of the cutoff affects the accuracy with which a low-beam headlamp can be vertically aimed. However, a number of issues have not been resolved. The present study was undertaken to address two of these issues: (1) how background light on the aiming screen affects visual aiming, and (2) whether the training and experience of the person dioing the aiming affect aiming performance. Two experiments on visual aiming were conducted. The results demonstrate clear effects of ambient illumination of the aiming screen on the mean position set by visual aiming, but provide no evidence for an effect on variability of visual aiming up to the maximtlm level examined, 108 lux. The effects on mean aim, although highly significant statistically, are not large relative to estimates of the current variability of headlamp vertical aim in the. United States. The present results therefore suggest that, at least up to 108 lux, ambient illumination of the aiming screen will not have significant detrimental effects on visual aiming of low-beam headlamps. The present results also indicate that special training, at least at the level of professional mechanics, does not affect aiming ability. This suggests that the average vehicle owner would have adequate success in aiming headlamps visually. (Author/publisher)
Abstract