This analytical study examined the potential benefits of applying two embodiments of adaptive lighting to the U.S. and European low-beam patterns: curve lighting that involves shifting the beam horizontally into the curve, and motorway lighting that involves shifting the beam vertically upward.
The curve lighting simulations paired 240-m radius left and right curves with a horizontal shift of 10°, and 80-m radius curves with a horizontal beam shift of 15°. The motorway lighting simulations involved upward aim shifts of 0.25° and 0.5°. For both curve and motorway lighting, changes in both seeing and glare illuminance were considered. Market-weighted model year 2000 U.S. and European beam patterns were used.
We conclude that curve lighting, as simulated here, would substantially improve seeing performance on curves for both types of beams. On right curves (but not on left curves) there would be an increase in disability glare for oncoming traffic. (Because there will not always be an opposing vehicle, disability effects will be somewhat less frequent than the visibility benefits, which will apply to every curve.) No major discomfort-glare problems would be expected. Although the shifted U.S. beams performed slightly better overall than the shifted European beams, the main difference in performance is between the shifted and nominally aimed beams.
Motorway lighting, as simulated here, would also substantially improve seeing performance, with the benefits already present at an upward shift of 0.25°. Because the increases in glare illuminance would be minor, and because motorways often incorporate median barriers or wide separations between lanes of opposing traffic, we do not expect substantial problems with increased glare. The European beams benefit more from this embodiment of motorway lighting than do the U.S. beams. (This is the case because under nominal aim the European beams provide less visibility illuminance and their vertical gradient is steeper.) Nevertheless, the nominally aimed U.S. beams tend to outperform the European beams shifted upward 0.25°.