Benefits of applying adaptive lighting to the U.S. and European low-beam patterns

Abstract

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 80-m radius left and right curves with a horizontal beam shift of 15°, and 240-m radius curves with a shift of 10°. The motorway lighting simulations involved upward aim shifts of 0.25° and 0.5°. For both curve and motorway lighting, changes in both visibility and glare illuminance were considered. Marketweighted 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 left curves (but not on right curves) there would be an increase in disability glare for oncoming traffic. No major discomfort glare problems would be expected. Although the shifted U.S. beams were found to perform 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°.