Quantifying the Benefits of Variable Reflectance Rearview Mirrors

We collected photometric data, concerning the simultaneous levels of rearview mirror glare and luminance of the forward scene, in order to characterize the night driving environment for rearview mirrors. An instrumented vehicle was used to collect photometric data for each combination of three road types (urban, expressway, and rural) with two pavement conditions (dry and wet). We then used these data to quantify the benefits of variable-reflectance rearview mirrors relative to (1) fixed-reflectance mirrors, and (2) two-level prism mirrors. The performance of the various types of mirrors was quantified in terms of a figure of merit. The figure of merit is simply the percentage of the time that all of three mirror-performance measures are met: (1) discomfort glare, (2) forward visibility, and (3) rearward visibility.

Results of the model indicate that variable reflectance mirrors offer substantial improvements, both as replacements for prism mirrors in the center mirror position, and, additionally, as replacements for fixed reflectance driver-side mirrors. The advantages are present in approximately equal magnitudes for most combinations of road type and pavement condition.