Evaluation of Meeting Beams of Two- and Three-Beam Headlighting Systems

The major objective of the study was to provide another indication of the validity of a computer simulation model for predicting visibility with headlight beams. A comparison was made of simulation results with those obtained in a field test of five beams for targets positioned at the right and left side of the lane. The agreement obtained was generally good throughout the meeting. The discrepancy between simulation and field test results was greatest for the visibility of targets at the right side of the lane when the vehicles were close to the meeting point. This error was explained as due to the differences in the field test visibility distances used as the comparison data compared to the results of the field studies that were done to provide initial validation of the model. The maximum extent of this error was about 20%. The results show that the model predicts within the error of the field test procedures. While there were no differences between the low beams or the mid beams for visibility of targets at the left of the lane, increases in visibility of up to 30% were attained with mid beams compared to the U.S. or E.C.E. low beams for visibility of targets at the right edge of the lane. An improved headlighting meeting beam configuration was suggested consisting of the E.C.E. low beams, for urban driving, and adding a lamp similar to the Type III lamp to form a mid beam for use as a meeting beam on rural roads.