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Publication Number: FHWA-HRT-04-135
Date: December 2005

Enhanced Night Visibility, Volume IV: Phase II—Study 2: Visual Performance During Nighttime Driving in Rain

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U.S. Department of Transportation

Federal Highway Administration

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296


FOREWORD

The overall goal of the Federal Highway Administration’s (FHWA) Visibility Research Program is to enhance the safety of road users through near-term improvements of the visibility on and along the roadway. The program also promotes the advancement of new practices and technologies to improve visibility on a cost-effective basis.

The following document summarizes the results of a study on the visual performance of drivers during nighttime driving in rain. The study was conducted under Phase II of the Enhanced Night Visibility (ENV) project, a comprehensive evaluation of evolving and proposed headlamp technologies under various weather conditions. The individual studies within the overall project are documented in an 18-volume series of FHWA reports, of which this is Volume IV. It is anticipated that the reader will select those volumes that provide information of specific interest.

This report will be of interest to headlamp designers, automobile manufacturers and consumers, third-party headlamp manufacturers, human factors engineers, and people involved in headlamp and roadway specifications.

 

Michael F. Trentacoste
Director, Office of Safety
    Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.
FHWA-HRT-04-135

2. Government Accession No.

3. Recipient’s Catalog No.

4. Title and Subtitle
Enhanced Night Visibility Series, Volume IV:
Phase II—Study 2: Visual Performance During Nighttime Driving in Rain

5. Report Date
December 2005

6. Performing Organization Code

7. Author(s)
Myra Blanco, Jonathan M. Hankey, Thomas A. Dingus

8. Performing Organization Report No.

9. Performing Organization Name and Address
Virginia Tech Transportation Institute
3500 Transportation Research Plaza
Blacksburg, VA 24061

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
DTFH61-98-C-00049

12. Sponsoring Agency Name and Address
Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13.Type of Report and Period Covered
Final Report

14. Sponsoring Agency Code
HRDS-05

15. Supplementary Notes
Contracting Officer’s Technical Representative (COTR): Carl Andersen, HRDS-05

16. Abstract
Phase II, Study 2 (rainy weather) was performed following the same procedures used for Study 1 (clear weather). Study 2 helped expand the knowledge of how current vision enhancement systems can affect detection and recognition of different types of objects while driving during adverse weather, specifically during rain conditions. The empirical testing for this study was performed on the Virginia Smart Road; the rain was controlled by weathermaking equipment. Thirty participants were involved in the study. A 12 by 7 by 3 mixed factorial design was used to investigate the effects of different types of vision enhancement systems, different types of objects on the roadway, and driver’s age on detection and recognition distances; subjective evaluations also were obtained for the different vision enhancement systems.

The results of the empirical testing suggest that vision enhancement systems that include halogen headlamps as their main component (i.e., halogen alone or halogen with ultraviolet A) consistently allow drivers the best detections during rain conditions. In fact, the halogen headlamp (low-beam configuration) provides the longest detection and recognition distances overall; in the few trials where other systems allow farther detection distances, these differences did not represent meaningful improvements. Even drivers using the infrared thermal imaging system, which resulted in farther detection distances for pedestrians and cyclists under clear conditions, perform no differently in the rain than when only the low beams of the vehicle were used.

17. Key Words
Age, Cyclist, Detection, Halogen, Headlamp, High Intensity Discharge (HID), Infrared, Night Vision, Nighttime, Pedestrian, Rain, Recognition, Vision Enhancement System, Weather

18. Distribution Statement
No restrictions. This document is available through the National Technical Information Service; Springfield, Virginia 22161.

19. Security Classif. (of this report)
Unclassified

20. Security Classif. (of this page)
Unclassified

21. No. of Pages
141

22. Price

Form DOT F 1700.7 (8-72)          Reproduction of completed page authorized


SI* (Modern Metric) Conversion Factors


ENHANCED NIGHT VISIBILITY PROJECT REPORT SERIES

This volume is the fourth of 18 volumes in this research report series. Each volume is a different study or summary, and any reference to a report volume in this series will be referenced in the text as “ENV Volume I,” “ENV Volume II,” etc. A list of the report volumes follows:

Volume Title Report Number
  I           Enhanced Night Visibility Series: Executive Summary FHWA-HRT-04-132
  II           Enhanced Night Visibility Series: Overview of Phase I and
Development of Phase II Experimental Plan
FHWA-HRT-04-133
  III           Enhanced Night Visibility Series: Phase II—Study 1: Visual
Performance During Nighttime Driving in Clear Weather
FHWA-HRT-04-134
  IV           Enhanced Night Visibility Series: Phase II—Study 2: Visual
Performance During Nighttime Driving in Rain
FHWA-HRT-04-135
  V           Enhanced Night Visibility Series: Phase II—Study 3: Visual
Performance During Nighttime Driving in Snow
FHWA-HRT-04-136
  VI           Enhanced Night Visibility Series: Phase II—Study 4: Visual
Performance During Nighttime Driving in Fog
FHWA-HRT-04-137
  VII           Enhanced Night Visibility Series: Phase II—Study 5: Evaluation of
Discomfort Glare During Nighttime Driving in Clear Weather
FHWA-HRT-04-138
  VIII           Enhanced Night Visibility Series: Phase II—Study 6: Detection of
Pavement Markings During Nighttime Driving in Clear Weather
FHWA-HRT-04-139
  IX           Enhanced Night Visibility Series: Phase II—Characterization of
Experimental Objects
FHWA-HRT-04-140
  X           Enhanced Night Visibility Series: Phase II—Visual Performance
Simulation Software for Objects and Traffic Control Devices
FHWA-HRT-04-141
  XI           Enhanced Night Visibility Series: Phase II—Cost-Benefit Analysis FHWA-HRT-04-142
  XII           Enhanced Night Visibility Series: Overview of Phase II and
Development of Phase III Experimental Plan
FHWA-HRT-04-143
  XIII           Enhanced Night Visibility Series: Phase III—Study 1: Comparison
of Near Infrared, Far Infrared, High Intensity Discharge, and Halogen Headlamps on Object Detection in Nighttime Clear Weather
FHWA-HRT-04-144
  XIV           Enhanced Night Visibility Series: Phase III—Study 2: Comparison
of Near Infrared, Far Infrared, and Halogen Headlamps on Object Detection in Nighttime Rain
FHWA-HRT-04-145
  XV           Enhanced Night Visibility Series: Phase III—Study 3: Influence of
Beam Characteristics on Discomfort and Disability Glare
FHWA-HRT-04-146
  XVI           Enhanced Night Visibility Series: Phase III—Characterization of
Experimental Objects
FHWA-HRT-04-147
  XVII           Enhanced Night Visibility Series: Phases II and III—
Characterization of Experimental Vision Enhancement Systems
FHWA-HRT-04-148
  XVIII           Enhanced Night Visibility Series: Overview of Phase III FHWA-HRT-04-149

TABLE OF CONTENTS

CHAPTER 1—INTRODUCTION

CHAPTER 2—METHODS CHAPTER 3—RESULTS CHAPTER 4—DISCUSSION AND CONCLUSIONS APPENDIX A—SCREENING QUESTIONNAIRE
APPENDIX B—INFORMED CONSENT FORM
APPENDIX C—VISION TEST FORM
APPENDIX D—TRAINING PROTOCOL
APPENDIX E—TRAINING SLIDES
APPENDIX F—IN-VEHICLE EXPERIMENTAL PROTOCOL
APPENDIX G—SMART ROAD
APPENDIX H—DEBRIEFING FORM
APPENDIX I—ONROAD EXPERIMENTER’S PROTOCOL
APPENDIX J—AIMING PROTOCOL
APPENDIX K—VALET PROTOCOL

REFERENCES

LIST OF FIGURES

  1. Photo. Pedestrian in black clothing.
  2. Photo. Cyclist in white clothing.
  3. Photo. Pedestrian in white clothing.
  4. Photo. Child’s bicycle.
  5. Photo. Tire tread.
  6. Diagram. Data collection display screen.
  7. Photo. Five or three UV–A + HLB.
  8. Photo. HOH or HHB.
  9. Photo. Hybrid UV–A + HID.
  10. Photo. HLB–LP with IR–TIS.
  11. Photo. Smart Road.
  12. Photo. Smart Road rain towers.
  13. Diagram. Locations where the objects were presented for the adverse weather condition (note the area where rain was generated).
  14. Bar graph. Results for the interaction: VES by Object by Age for IR–TIS.
  15. Bar graph. Results for the interaction: VES by Object by Age for HLB–LP.
  16. Bar graph. Results for the interaction: VES by Object by Age for HOH.
  17. Bar graph. Results for the interaction: VES by Object by Age for HHB.
  18. Bar graph. Results for the interaction: VES by Object by Age for five UV–A + HLB.
  19. Bar graph. Results for the interaction: VES by Object by Age for three UV–A + HLB.
  20. Bar graph. Results for the interaction: VES by Object by Age for hybrid UV–A + HLB.
  21. Bar graph. Results for the interaction: VES by Object by Age for HLB.
  22. Bar graph. Results for the interaction: VES by Object by Age for five UV–A + HID.
  23. Bar graph. Results for the interaction: VES by Object by Age for three UV–A + HID.
  24. Bar graph. Results for the interaction: VES by Object by Age for hybrid UV–A + HID.
  25. Bar graph. Results for the interaction: VES by Object by Age for HID.
  26. Bar graph. Results on detection distances for the VES by Object interaction for pedestrians and cyclist with white clothing.
  27. Bar graph. Results on detection distances for the VES by Object interaction for pedestrians with black clothing and other objects.
  28. Bar graph. Results on recognition distances for the VES by Object interaction for pedestrians and cyclist with white clothing.
  29. Bar graph. Results on recognition distances for the VES by Object interaction for pedestrians with black clothing and other objects.
  30. Bar graph. Bonferroni post hoc results for the main effect: VES.
  31. Bar graph. Bonferroni post hoc results for main effect: Object.
  32. Bar graph. Bonferroni post hoc results on the ratings evaluating detection for the main effect: VES.
  33. Bar graph. Bonferroni post hoc results on the ratings evaluating recognition for the main effect: VES.
  34. Bar graph. Bonferroni post hoc results on the ratings evaluating lane-keeping assistance for the main effect: VES.
  35. Bar graph. Bonferroni post hoc results on the ratings evaluating roadway direction for the main effect: VES.
  36. Bar graph. Bonferroni post hoc results on the ratings evaluating visual discomfort for the main effect: VES.
  37. Bar graph. Bonferroni post hoc results on the ratings evaluating overall safety for the main effect: VES.
  38. Bar graph. Bonferroni post hoc results on the overall rating for the main effect: VES.
  39. Equation. Braking distance.
  40. Equation. Total stopping distance for brake reaction time plus braking distance.
  41. Equation. AASHTO calculation of coefficient of friction for wet pavement.
  42. Bar graph. Participants’ visual acuity divided by age group.
  43. Bar graph. Participants’ contrast sensitivity at 1.5 cpd (cycles per degree) divided by age group.
  44. Bar graph. Participants’ contrast sensitivity at 3.0 cpd divided by age group.
  45. Bar graph. Participants’ contrast sensitivity at 6.0 cpd divided by age group.
  46. Bar graph. Participants’ contrast sensitivity at 12.0 cpd divided by age group.
  47. Bar graph. Participants’ contrast sensitivity at 18.0 cpd divided by age group.
  48. Photo. Smart Road testing facility.


LIST OF TABLES

  1. Experimental design: 12 by 3 by 7 mixed-factor design (12 VES configurations, 3 age groups, 7 objects—see table 2 for objects).
  2. Seven objects presented in each cell of table 1.
  3. Example of the VES configuration order for a pair of participants.
  4. Description of the objects.
  5. Model for the experimental design.
  6. ANOVA summary table for the dependent measurement: detection distance.
  7. ANOVA summary table for the dependent measurement: recognition distance.
  8. Summary of significant main effects and interactions.
  9. ANOVA summary table for the Likert-type rating for detection.
  10. ANOVA summary table for the Likert-type rating for recognition.
  11. ANOVA summary table for the Likert-type rating for lane-keeping assistance.
  12. ANOVA summary table for the Likert-type rating for roadway direction.
  13. ANOVA summary table for the Likert-type rating for visual discomfort.
  14. ANOVA summary table for the Likert-type rating for overall safety rating.
  15. ANOVA summary table for the Likert-type rating for overall VES evaluation.
  16. Summary of significant main effects and interactions for the Likert-type rating scales.
  17. Mean detection and recognition distances during nighttime driving in rain.
  18. Difference in reaction time available depending on vehicle speed, based on the difference of detection time from HLB in seconds.
  19. Differences in detection distances between clear and rain environments.
  20. Stopping distances needed for a wet roadway.
  21. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: IR–TIS.
  22. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: five UV–A + HLB.
  23. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: three UV–A + HLB.
  24. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: hybrid UV–A + HLB.
  25. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: HLB.
  26. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: HOH.
  27. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: HHB.
  28. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: five UV–A + HID.
  29. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: three UV–A + HID.
  30. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: hybrid UV–A + HID.
  31. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: HID.
  32. Detection distances by type of object and potential detection inadequacy when compared to stopping distance at various speeds: HLB–LP.
  33. Detection distance differences by VES and type of object.
  34. Detection distance difference between the different VESs and HLB.
  35. Percentage of detection distance difference between the different VESs and HLB.
  36. Mean recognition distance differences by VES and type of object.
  37. Recognition distance difference between the different VESs and HLB.
  38. Percentage of difference between the different VESs and HLB.

LIST OF ACRONYMS AND ABBREVIATIONS

 

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