G. Adachi

Michael J. Flannagan

M. Sivak

Brandon Schoettle

This study was designed to compare the illuminated surface areas of HID and tungstenhalogen low-beam headlamps in the U.S. A sample of 20 tungsten-halogen lamps and 17 HID lamps for model year 2000 vehicles in the U.S. was examined. The illuminated surface area was determined using a modified version of an ECE method for evaluating the illuminated surface of signaling devices. The main finding is that the HID low beams generally have smaller illuminated surface areas than do the tungsten-halogen low beams. Because smaller light sources result in more discomfort glare (presumably via greater luminance), the present finding suggests that the smaller illuminated area is one reason for drivers reporting more discomfort from HID lamps. An implication is that the increased discomfort from HID lamps could be reduced by increasing their illuminated surface area.

The Illuminated Surface Areas of HID and Tungsten-halogen Headlamps in the U.S.

Y. Nakata

This analytical study compared the median beam pattern of a sample of 19 HID low beams manufactured for model year 2000 vehicles sold in the U.S. with a market-weighted median beam pattern of tungsten-halogen lamps for vehicles of the same model year. The results indicate that the HID lamps tended to provide wider beam patterns than did the tungsten-halogen lamps, which, in turn, should improve the visibility of pedestrians on curves and may make the lane-maintenance task less demanding. On right curves, there was an increase in glare illumination towards oncoming drivers, while on left curves there was a decrease in glare illumination. On straight roads, the HID lamps produced more illumination for pedestrians and road delineation on the left side of the road. This was also the case for the right side of the road, but only for the projector HID lamps; the nonprojector HID lamps produced less illumination at the relevant locations than did the tungsten-halogen lamps. Finally, on straight roads HID lamps produced less glare for oncoming drivers than did the tungstenhalogen lamps. The results for traffic-sign illumination varied with the location of the sign.HID lamps produce more light than do tungsten-halogen lamps. Consequently, they hold great promise for improving the nighttime safety of driving by improving the lowbeam light distribution. The present analysis indicates that this promise has already been partially met in the first generation of HID lamps on vehicles in the U.S.

Brandon Schoettle

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