Using PC-detect to compare United States and European beam patterns.

This paper describes the results of comparison of the performance of U.S. and European low beams with the PCDETECT seeing distance model developed by the Ford Motor Company. PCDETECT is a revised version of the DETECT seeing distance model, developed by Ford in 1975, and is programmed to run on IBM PCs and compatibles. The beam patterns studied were the U.S. H4656 low beam and the European Granada H4 low beam. These lamps have very similar performance as measured by the Ford CHESS headlamp evaluation program. PCDETECT was used to compare the seeing distance performance of the lamps, under conditions likely to reflect the differences in the beam patterns. On level roads and in mild horizontal curves, a correctly aimed European low beam performed as well as or better than U.S. beams for objects on or near the road surface. The European beam provided substantially less illumination of overhead traffic signs than the U.S. beam, resulting in shorter legibility distances. Also, the European beam was generally more sensitive to misaim than the U.S. beam and gave significantly lower seeing distances to pedestrians and pavement lines. Finally, seeing distance to pedestrians and pavement delineation on sag vertical curves (valleys) was substanially less with the European beam. (A) For the covering abstract of the conference, see IRRD 837684.