This study evaluated several recent proposals for the low-beam headlighting pattern. The research consisted of (1) documenting the current U.S., European, and Japanese standards; (2) documenting the proposed low-beam patterns; (3) performing a comparative analysis of the proposed beam patterns; (4) developing a set of visual performance functions for low-beam headlamps; (5) defining the representative geometry for the visual performance functions; (6) setting criterion illuminance values for the visual performance functions based on available empirical data; and (7) evaluating the standards and proposals in relation to the criterion values by considering the worst allowed case. The following are the main findings: (a) There is a lack of empirical evidence for evaluating the proposals on certain performance functions, including visual aim, effects of misaim, and homogeneity of the beam; (b) In terms of visibility, none of the proposals (nor existing standards) met our criterion of 33 lux for seeing low-contrast targets on the right side of the road, supporting the notion that we commonly overdrive our low beam headlamps; (c) Because the functional requirements of low beams are multifaceted and complex, it is not surprising that each proposal and standard has its advantages and disadvantages; (d) The relation between seeing illuminance and glare illuminance is likely to capture a substantial part of the functional requirements of low beams; and (e) The proposals by P. Padmos and J.W.A.M. Alferdinck (explicitly designed to optimize European-type low beam) had the best mean ranking across the individual performance functions. The SAE proposal (based on the current U.S.-type beam, but implicitly designed to bridge the gap between the U.S. and European beams) had the second best mean ranking. (A)
Abstract