The Distribution of Visibility Levels at Target Detection in a Modified Adrian/CIE Visibility Model

摘要

Adrian's Visibility Model is a useful tool for assessing the visibility of an object at night and has been accepted as the Small Target Visibility (STV) design criteria in the Illuminating Engineering Society's American National Standard Practice for Roadway Lighting. In this study, a modified model has been used which incorporates more recent findings involving glare sources. Previous work has shown that the average visibility level (VL) at target detection will vary depending upon the observer's age, headlight beam pattern, and target reflectivity. However, the population distribution of VL at detection was still uncertain making it difficult to assess confidence in detection calculations. This study has mined available data to determine the distribution of VLs at target detection for a driving subject group. A log-normal fit has been generated for alerted and unalerted subjects which demonstrates the wide range of values that must be considered for confidence in accident avoidance analyses.