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Publication Number: FHWA-HRT-04-137
Date: December 2005

Enhanced Night Visibility Series, Volume VI: Phase II—Study 4: Visual Performance During Nighttime Driving in Fog

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Figure 1. Photo. Perpendicular pedestrian in white clothing. This daylight photo shows the object used in the study. The photograph shows a side view of a person wearing a white short-sleeved shirt over a black long-sleeved shirt, white pants, black ski cap with face mask, protective glasses, dark boots, and gloves. The person is standing against a plain background. Back to Figure 1.

Figure 2. Diagram. Data collection display screen. The graphic shows a sample display screen used to record the data collected during an onroad trial. The top section identifies the driver and passenger by participant ID, age, and gender. The middle section describes the trial setup, including the vehicle enhancement system, target order, day, participant number, output file name, and specific experiment being conducted. The bottom section allows the experimenter to see the object order used in the trial and record the driver and passenger detection and recognition distances. Back to Figure 2.

Figure 3. Photo. Five UV–A + HLB. The photo shows the front end of a white SUV with the headlamps removed and a modular light rack attached. In front of where the vehicle’s own headlamps would be are two HLB headlamps. Taking up almost all the space between them are three round, black UV–A headlamps. Two more UV–A headlamps hang beneath the HLB headlamps. Back to Figure 3.

Figure 4. Photo. Hybrid UV–A + HLB. The photo shows two hybrid UV–A headlamps and two halogen low beam headlamps attached to the front of an experimental SUV with a modular light rack. The halogen low beam headlamps are mounted on the far right and far left front, and the hybrid UV–A lights are mounted adjacent to them toward the center of the vehicle. Back to Figure 4.

Figure 5. Photo. HID. The photo shows two high intensity discharge headlamps attached to the front of an experimental SUV with a modular light rack. The headlamps are mounted on the far right and far left front of the vehicle. Back to Figure 5.

Figure 6. Photo. HLB–LP with IR–TIS. The photo shows the front of the experimental sedan used in the study. The sedan is equipped with standard halogen low beam headlamps. In the center of the front grille, there is a circular opening for the infrared camera, indicating the presence of the infrared thermal imaging system. Back to Figure 6.

Figure 7. Photo. Smart Road. The daylight photo is an aerial view of a section of the Virginia Smart Road. The section of road is fairly straight with one gradual curve. The photo shows that there are no other structures in the immediate vicinity. Back to Figure 7.

Figure 8. Diagram. Locations where pedestrians were presented for the adverse weather condition (note the area where fog was generated). The diagram shows the entire length of the Smart Road. The road is depicted as being fairly straight with one gradual curve up toward the top. There is a turnaround loop at each end of the road. The top turnaround is in the upper left corner of the diagram, and the bottom turnaround is in the lower right corner, indicating that there is a grade. In addition to the two turnarounds at either end, there are two small turnarounds labeled “Turnaround 2” and “Turnaround 3” on either end of a road section labeled “Adverse Weather Testing Area Where Fog was Generated.” A legend contains an arrow labeled as “Object Location.” In this road section, there are four arrows along the side of the road, indicating the four locations where the object was presented. Locations 1 and 2 are on one side of the road, indicating that a driver would see the object during the drive from the top to the bottom of the road. Location 4 is nearly opposite Location 2, and Location 5 is nearly opposite Location 1, indicating that a driver would see the object during the drive from the bottom of the road to the top. The diagram shows that all locations are on straight sections of the road. Back to Figure 8.

Figure 9. Diagram. Fog tower generating fog. The diagram shows a fog tower producing fog over the roadway. The fog tower is depicted as a pipe-like structure mounted outside the guardrail. The pipe reaches high above the guardrail at about a 45-degree angle until it is above the pavement. There, a smaller pipe reaches out over the roadway, and it is positioned parallel to the road. The diagram shows the tower spraying fog in the form of swirls onto the roadway. Back to Figure 9.

Figure 10. Photo. Smart Road overhead lighting system and fog towers starting to make fog. A note says lights were turned off for study. The photo shows a section of road equipped with overhead lighting and a series of fog towers. The photo is taken at night, and both the overhead lighting system and the fog towers are operating. The portion of the fog towers that are visible in the picture are the arms and nozzles that reach out high above the roadway near the lighting system. The arms of the towers are parallel to the roadway, and fog is billowing out of them. Back to Figure 10.

Figure 11. Bar graph. Bonferroni post hoc results for the main effect: VES. The graph is titled “Detection and Recognition Distances by VES for the Fog Condition.” The X-axis is labeled “Vision Enhancement System (HLB equals baseline),” and the Y-axis is labeled “Mean Distance (Unit: Feet).” There are two sets of bars for each VES, one representing the detection distance and one representing the recognition distance. Standard error bars are present for each bar, and letters above the bars show the Bonferroni groupings. The detection distances for the VESs range from approximately 140 feet with HID to approximately 190 feet with IR–TIS and five UV–A + HLB. The recognition distances range from approximately 130 feet with HID to approximately 175 feet with five UV–A + HLB. Standard errors are small and generally comparable across the VESs. The Bonferroni groupings are the same for detection and recognition distances. IR–TIS, five UV–A + HLB, hybrid UV–A + HLB, and HLB are in the longest detection and recognition distance group; hybrid UV–A + HLB, HLB, and HLB–LP are in the next longest group; and hybrid UV–A + HLB, HID, and HLB–LP are in the shortest group. Back to Figure 11.

Figure 12. Bar graph. Bonferroni post hoc results for the main effect: age. The graph is titled “Detection and Recognition Distances by Age Group for the Fog Condition.” The X-axis is labeled “Age Group,” and the Y-axis is labeled “Mean Distance (Unit: Feet).” There are two sets of bars for each age group, one representing the detection distance and one representing the recognition distance. Standard error bars are present on each bar and are generally small and comparable. Letters above the bars show the Bonferroni groupings. Detection distance ranges from approximately 150 feet for the young age group to approximately 175 feet for the older age group. Recognition distance ranges from approximately 140 feet for the young age group to 165 feet for the older age group. The Bonferroni groupings show that the detection and recognition distances for the younger age group were significantly smaller than the middle and older age groups, which are statistically grouped. Back to Figure 12.

Figure 13. Bonferroni post hoc results on the ratings evaluating detection for the main effect: VES. The graph is titled “Statement 1: This Vision Enhancement System allowed me to detect objects sooner than my regular headlights.” The X-axis is labeled “Vision Enhancement System (HLB equals Baseline),” and the Y-axis is labeled “Mean Rating” and has a scale from 1 (“Strongly Agree”) to 7 (“Strongly Disagree”). A bar with a standard error bar is present for each VES. The standard error across the VESs is generally similar, with IR–TIS producing a smaller standard error than the other VESs. The ratings range from approximately 1.3 with IR–TIS to approximately 3.2 with HLB–LP. A lower rating indicates a more desirable system. The baseline VES (HLB) received a mean rating of approximately 2.5. The Bonferroni groupings show that the rating for IR–TIS is significantly lower than all other VESs. HLB–LP rated significantly higher than five UV–A + HLB and hybrid UV–A + HLB. The baseline HLB is only significantly different from IR–TIS. Back to Figure 13.

Figure 14. Bar graph. Bonferroni post hoc results on the ratings evaluating recognition for the main effect: VES. The graph is titled “Statement 2: This Vision Enhancement System allowed me to recognize objects sooner than my regular headlights.” The X-axis is labeled “Vision Enhancement System (HLB equals baseline),” and the Y-axis is labeled “Mean Rating” and has a scale from 1 (“Strongly Agree”) to 7 (“Strongly Disagree”). A bar with a standard error bar is present for each VES. The standard error across the VESs is generally similar, with HID and HLB–LP producing slightly larger standard error than the other VESs. The ratings range from approximately 1.3 with IR–TIS to approximately 3.2 with HLB–LP. A lower rating indicates a more desirable system. The baseline VES (HLB) received a mean rating of approximately 2.5. The Bonferroni groupings show that the rating for IR–TIS is significantly lower than all VESs except for hybrid UV–A +HLB. The rating for HLB–LP was significantly larger than both IR–TIS and hybrid UV–A +HLB. Back to Figure 14.

Figure 15. Bar graph. Bonferroni post hoc results on the overall rating for the main effect: VES. The graph is titled “Statement 7: This is a better Vision Enhancement System than my regular headlights.” The X-axis is labeled “Vision Enhancement System (HLB equals Baseline),” and the Y-axis is labeled “Mean Rating” and has a scale from 1 (“Strongly Agree”) to 7 (“Strongly Disagree”). A bar with a standard error bar is present for each VES. The standard error across the VESs is generally similar, with IR–TIS producing a slightly smaller standard error than the other VESs. The ratings range from approximately 1.4 with IR–TIS to approximately 2.6 with HLB–LP. A lower rating indicates a more desirable system. The baseline VES (HLB) received a mean rating of approximately 2.4. The Bonferroni groupings show that the rating for IR–TIS is significantly lower than five UV–A +HLB and HLB–LP. The ratings for the other VESs were not significantly different from one another. Back to Figure 15.

Figure 16. Scatter plot. Young drivers’ detection versus recognition distances. The graph is titled “Young.” The X-axis is labeled “Recognition Distance (unit in feet),” and the Y-axis is labeled “Detection Distance (unit:in feet).” The graph shows a strong positive relationship between detection distance and recognition distance. The detection distances range from 0 to approximately 325 feet. Recognition distances range from 0 to approximately 290 feet. The majority of the data points are grouped between approximately 50 feet for detection and recognition to approximately 325 feet for detection and 290 feet for recognition. Back to Figure 16.

Figure 17. Scatter plot. Middle-aged drivers’ detection versus recognition distances. The graph is titled “Middle-Age.” The X-axis is labeled “Recognition Distance (unit in feet),” and the Y-axis is labeled “Detection Distance (unit in feet).” The graph shows a strong positive relationship between detection distance and recognition distance. The detection distances range from approximately 10 to 440 feet. Recognition distances range from approximately 10 to approximately 410 feet. The majority of the data points are grouped between approximately 10 feet for detection and recognition to approximately 320 feet for detection and recognition. Two points are outliers; one with detection and recognition distances of approximately 350 feet, and another with a detection distance of approximately 440 feet and a corresponding recognition distance of approximately 410 feet. Back to Figure 17.

Figure 18. Scatter plot. Older drivers’ detection versus recognition distances. The graph is titled “Older.” The X-axis is labeled “Recognition Distance (unit in feet),” and the Y-axis is labeled “Detection Distance (unit in feet).” The graph shows a strong positive relationship between detection distance and recognition distance. The detection distances range from approximately 25 to 380 feet. Recognition distances range from approximately 25 to approximately 380 feet. The majority of the data points are grouped between approximately 50 feet for detection and recognition to approximately 320 feet for detection and recognition. One point is an outlier with a detection distance of approximately 380 feet and a corresponding recognition distance of approximately 380 feet. Back to Figure 18.

Figure 19. Bar graph. Participants’ visual acuity divided by age group. The X-axis is labeled “Acuity,” and the Y-axis is labeled “Number of Participants.” The X axis shows six different categories of acuity ranging from 20/13 to 20/40. Different bars represent the number of participants from the different age groups that fall into the different categories. Acuity scores for the young participants range from 20/13 to 20/25 and create a bell-shaped curve. Acuity scores for the middle-aged participants range from 20/13 to 20/25, with half of the middle-aged participants falling in the 20/20 category. Acuity scores for the older participants range from 20/20 to 20/40, with 6 out of the 10 falling in the 20/20 category. Back to Figure 19.

Figure 20. Bar graph. Participants’ contrast sensitivity at 1.5 cpd (cycles per degree) divided by age group. The Y-axis is labeled “Number of Participants.” The X-axis is labeled “Percentage of Contrast at 1.5 cpd.” The X-axis is split in half with the percentage of contrast values for the left eye on one side and the percentage of contrast values for the right eye on the other. The percentage of contrast values listed on the X-axis range from 0.59 (“Good”) to 5 (“Poor”) for each eye. There are three styles of bars, each one representing the participants in an age group (young, middle, or older). Participants in the younger and middle age groups ranged from 0.83 to 2.86. Participants in the older age group ranged from 0.83 to 2.86, with the majority falling into the 2.86 category. Back to Figure 20.

Figure 21. Bar graph. Participants’ contrast sensitivity at 3.0 cpd divided by age group. The Y-axis is labeled “Number of Participants.” The X-axis is labeled “Percentage of Contrast at 3.0 cpd.” The X-axis is split in half, with the percentage of contrast values for the left eye on one side and the percentage of contrast values for the right eye on the other. The percentage of contrast values listed on the X-axis range from 0.45 (“Good”) to 4.17 (“Poor”) for each eye. There are three styles of bars, each one representing the participants in an age group (young, middle, or older). The younger participants ranged from 0.45 to 1.13 percent contrast sensitivity, with the majority of them falling into the 0.59 category. Middle-aged participants were split between the 0.59 and 1.13 categories. Older participants ranged from 0.45 to 2.27. Back to Figure 21.

Figure 22. Bar graph. Participants’ contrast sensitivity at 6.0 cpd divided by age group. The Y-axis is labeled “Number of Participants.” The X-axis is labeled “Percentage of Contrast at 6.0 cpd.” The X-axis is split in half, with the percentage of contrast values for the left eye on one side and the percentage of contrast values for the right eye on the other. The percentage of contrast values listed on the X-axis range from 0.38 (“Good”) to 4.76 (“Poor”) for each eye. There are three styles of bars, each one representing the participants in an age group (young, middle, or older). Younger participants ranged from 0.38 to 2.22 with the majority seeing either 0.54 percent of contrast or 0.8 percent of contrast. The range for the middle age group was 0.54 to 1.43. The older age group showed a trend toward the poor end of the scale, with half of them falling into the 1.43 percent of contrast category or poorer. Back to Figure 22.

Figure 23. Bar graph. Participants’ contrast sensitivity at 12.0 cpd divided by age group. The Y-axis is labeled “Number of Participants.” The X-axis is labeled “Percentage of Contrast at 12.0 cpd.” The X-axis is split in half, with the percentage of contrast values for the left eye on one side and the percentage of contrast values for the right eye on the other. The percentage of contrast values listed on the X-axis range from 0.59 (“Good”) to 12.5 (“Poor”) for each eye. There are three styles of bars, each one representing the participants in an age group (young, middle, or older). Approximately 70 percent of the younger age group could see 1.14 percent of contrast or less. The middle age group ranged from 0.8 to 6.67. The older age group showed a trend toward the poor end of the scale, with half of them falling into the 6.67 and 12.5 categories. Back to Figure 23.

Figure 24. Bar graph. Participants’ contrast sensitivity at 18.0 cpd divided by age group. The Y-axis is labeled “Number of Participants.” The X-axis is labeled “Percentage of Contrast at 18.0 cpd.” The X-axis is split in half, with percentage of contrast values for the left eye on one side and the percentage of contrast values for the right eye on the other. The percentage of contrast values listed on the X-axis range from 1.11 (“Good”) to 25 (“Poor”) for each eye. There are three styles of bars, each one representing the participants in an age group (young, middle, or older). Approximately 80 percent of the young age group could see 3.85 percent of contrast or less. The middle age group generally fell into the 3.85 and 6.67 percent of contrast categories. Approximately 60 percent of the older age group could see only 10 percent of contrast or greater. Back to Figure 24.

Figure 25. Equation. Braking distance. d subscript BD equals V squared divided by the following: the sum of f and uppercase G, end of sum, that sum multiplied by lowercase g, multiplied by 2. Back to Figure 25.

Figure 26. Equation. Total stopping distance for brake reaction time plus braking distance. d equals the following sum: 2.5 multiplied by V, that product plus the quotient of V squared divided by the product of 2 multiplied by g multiplied by f. Back to Figure 26.

Figure 27. Equation. AASHTO calculation of coefficient of friction for wet pavement. f equals a divided by g, which equals 11.2 feet per second squared divided by 32.2 feet per second squared, which equals 0.35. Back to Figure 27.

Appendix C: Contrast Sensitivity Test Diagram. The diagram shows the form the experimenters used to document the results for each participant’s contrast sensitivity exam. The diagram shows a graph with contrast sensitivity from 3 to 300 on the left Y-axis, contrast threshold from .3 to .003 on the right Y-axis, and spatial frequency (cycles per degree) from .5 to 6 on the X-axis. There is a column of numbered circles above each cycle per degree, indicating participant response. There are two diagrams, one for recording the results of the right eye and one for the results of the left eye. Return to Diagram.

Appendix E. Training Slide 1.

Enhanced Night Visibility

Schedule and Training

Experimenters:

Back to Slide 1.

Appendix E. Training Slide 2.

  • Schedule
  • Training
    • Driver’s License Verification
    • Informed Consent
    • Forms and Questionnaires
    • Vision Tests
    • Laboratory Training
    • In-vehicle Familiarization
Back to Slide 2.

Appendix E. Training Slide 3.
  • What is the Enhanced Night Visibility study?
  • What is enhanced night visibility?
  • Why is your help important?
  • Vehicles:
    • Car
    • SUV
  • Scenario:
    • Smart Road test facility
    • Nighttime
    • Weather: Clear, Rain, Snow, or Fog
Back to Slide 3.

Appendix E. Training Slide 4.
  • Lab Training
  • This training will help orient you to:
    • the Thermal Imaging System
    • the definition of terms we will use
    • the procedures
    • the objects
    • what we will ask from you

Back to Slide 4.

Appendix E. Training Slide 5.

The Smart Road

For this research effort, you will be driving on the Smart Road test facility.

The Smart Road will be closed off to all traffic other than research vehicles. As a result, there will be at most two vehicles moving on the road, including the one you are driving.

Back to Slide 5.

Appendix E. Training Slide 6. The slide shows an aerial photo of a portion of the Smart Road. Back to Slide 6.

Appendix E. Training Slide 7. The slide includes three separate photographs (one of a white SUV, one of a black SUV, and one of a sedan). All the photographs show the left side view of the vehicle and are taken from the back. The VESs are not visible in any of the photographs. The slide also includes the following text:
  • Experimental Vehicles
  • Vision Enhancement Systems
    • The Night Vision System
    • Prototype Headlamps
Back to Slide 7.

Appendix E. Training Slide 8.
  • Detection and Recognition
  • Your primary task is to drive safely
    • Training; 15 mph in gravel lot, 25 mph on paved road
    • 10 mph on Smart Road
  • Your job will be to detect and recognize different objects on the Smart Road
  • You will be required to press a button when you both detect and recognize objects
Back to Slide 8.

Appendix E. Training Slide 9.
  • Detection of Objects
  • Detection is when you can just tell that something is on the road in front of you.
    • Detection is important while driving in that it prepares you to possibly make an evasive action
  • When you detect an object, push the button as soon as you know something is in the road.
Back to Slide 9.

Appendix E. Training Slide 10.
  • Recognition of Objects
  • Recognition is when you can say for sure what the object is.
    • This provides you with more information so you can adequately react to the object
  • When you can recognize the object, you must push the button and, at the same time, identify the object to the experimenter by saying, “I see a _____.”
  • In case of an Unsuccessful Recognition press the push button again as soon as you notice what the right object is and tell the experimenter.
Back to Slide 10.

Appendix E. Training Slide 11.
  • Types of Objects
  • Dynamic Objects
    • Pedestrians: People will be walking along side or across the road.
    • Cyclists: People will be riding bicycles across the road.
Back to Slide 11.

Appendix E. Training Slide 12. This slide is titled “Dynamic Objects” and contains two separate photographs. One photograph is the side view of a person walking and wearing black clothing. The other photograph is the side view of a person riding a bicycle and wearing white clothing. Back to Slide 12.

Appendix E. Training Slide 13.
  • Questionnaires
  • You will be asked to respond to a questionnaire after each VES
    • Headlamp configuration questionnaire: You will provide a numbered rating of each headlight on a scale from 1 to 7.
    • Show questionnaires and different rating scales.
Back to Slide 13.

Appendix E. Training Slide 14.
What we need from you
Driving is the primary task, so use safe driving practices
Maintain the specified speed limit
Immediately push the button when you Detect and/or Recognize an object
Verbally identify all objects as you press the button for the Recognition portion
Respond to the questionnaires
Ask questions whenever you need to
Back to Slide 14.

Appendix E. Training Slide 15.

Questions?

Back to Slide 15.

Appendix K. Diagram of hotspot location for headlamp aiming. The diagram depicts a set of crosshairs centered on a large circle. Two smaller circles are centered horizontally inside the large circle. Two smaller circles are also centered vertically inside the larger circle, but portions of them are overlapped by the horizontal circles. The caption above the diagram says “Hotspot Location: The large outer circle represents the overall target area. The center of the large circle is the target hotspot location.” Return to Diagram.

Figure 28. Photo. Smart Road testing facility. This daylight photograph shows a paved road with a large turnaround at one end extending down into a valley at the other end. Back to Figure 28.

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