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Publication Number: FHWA-HRT-04-147
Date: December 2005

Enhanced Night Visibility Series, Volume XVI: Phase III—Characterization of Experimental Objects

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CHAPTER 1—INTRODUCTION

This project is a follow-on analysis to the study reported in Enhanced Night Visibility (ENV) Volume XIII, Phase III—Study 1: Comparison of Near Infrared, Far Infrared, High Intensity Discharge, and Halogen Headlamps on Object Detection in Nighttime Clear Weather (referred to as the IR Clear study). The IR Clear study evaluated six different automotive vision enhancement systems (VESs). Three of these were infrared (IR) systems, of which two were active near-IR systems, and the third was a passive far-IR system. The remaining three VESs were visible-light (VIS) systems; one was a standard halogen (i.e., tungsten-halogen) system used in previous ENV experiments, and two were high intensity discharge (HID) systems, each with a different beam distribution. In the basic experiment, the visibility of pedestrians, simulated animals, tire treads, and roadway infrastructure (e.g., signs and pavement markers) was tested with each of the VESs.

This follow-on investigation measured the photometric characteristics of the objects used in the experiment. The measurements were made using a charged coupled device (CCD) photometer with each of the VESs. The luminance of each object and the background behind it were derived from the photometric data. Then these values were used to model the contrast and visibility level of the object at the threshold of visibility.

The purpose of this investigation is to use the measured data as a tool to evaluate the capability of the VESs to provide adequate visibility of objects in the roadway. The photometric analysis provided insight into the performance of the VIS systems; however, it should be noted that the photometric analysis provided only a method of identifying the usage of the IR systems and not their photometric characteristics.

The following research questions for this project were drawn from the results of the IR Clear study documented in ENV Volume XIII:

  • Is there a relationship between measured data or calculated values and the visibility distance?
  • Because all of the photometric measurements are made at threshold of visibility, are the resulting contrast or visibility levels similar?
  • When does an IR system appear to be used by the driver?
  • Does having an IR system in the vehicle require higher object contrast and visibility levels at threshold than when the system is not used?
  • What is the effect of beam pattern on the visibility of the objects?

 

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