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• Enhanced Night Visibility, Volume V: Phase II—Study 3: Visual Performance During Nighttime Driving in Snow

Enhanced Night Visibility, Volume V: Phase II—Study 3: Visual Performance During Nighttime Driving in Snow

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

Figure 2. Photo. Parallel pedestrian in white clothing. This photograph shows one of the objects used in the study. It is a front 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, black boots, and gloves. The person is standing against a plain background. Back to Figure 2.

Figure 3. Photo. Perpendicular pedestrian in black clothing. This photograph shows one of the objects used in the study. It is a side view of a person dressed in black standing against a plain background. The person is wearing a ski cap with face mask, protective glasses, jacket, pants, boots, and gloves. Back to Figure 3.

Figure 4. Photo. Five UV-A + halogen low beam. The picture shows the front end of a white sport utility vehicle (SUV) with the headlamps removed and a modular light rack attached. In front of the vehicle's own headlamp sockets are two halogen low beam (HLB) headlamps. Taking up almost all the space between them are three round, black ultraviolet A (UV-A) headlamps. Two more UV-A lamps hang beneath the HLB lamps. Back to Figure 4.

Figure 5. Photo. Hybrid UV-A + halogen low beam. The picture shows the front end of a white SUV with a modular light rack attached. In front of the vehicle's own headlamps are two HLB headlamps. Between them are two slightly smaller, rectangular hybrid UV-A headlamps. Back to Figure 5.

Figure 6. Photo. High intensity discharge. The picture shows the front end of a white SUV with a modular light rack attached. In front of the vehicle's own headlamps are two high intensity discharge (HID) headlamps. Back to Figure 6.

Figure 7. Photo. Snowmaking on the Virginia Smart Road. The photo is a view of a section of the Virginia Smart Road with five snow towers spraying snow onto the road. The road is beginning to be covered by snow, but some pavement is still visible. The picture was taken during the day with no clouds. Back to Figure 7.

Figure 8. Diagram. Locations where objects were presented for the adverse weather condition (note the area where snow was generated). The diagram shows the entire course of the Virginia Smart Road that participants drove during the study. The road is depicted as being fairly straight with one gradual curve up toward the top and another before a middle area labeled "Adverse Weather Testing Area Where Snow Was Generated." 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. A note in the bottom left corner shows that an arrow represents an object location. Four arrows along the side of the road indicate the four locations where objects were presented. Locations 1 and 2 are on one side of the road, indicating that a driver would see objects stationed there during the drive from the top to the bottom of the road. Locations 4 and 5 are on the opposite side of the road from the first two locations, indicating that a driver would see objects placed there during the drive from the bottom of the road to the top of the road. Locations 1, 2, 4, and 5 are all grouped toward the middle segment of the course. Locations 1 and 5 are close together but on opposite sides of the road. Locations 2 and 4 are also close together, but on opposite sides of the road. The diagram shows that all locations are on straight sections of the road.
Back to Figure 8.

Figure 9. Bar graph. Bonferroni post hoc results on detection and recognition distances for the main effect: VES (means with the same letter are not significantly different). This bar graph compares the four VESs in a Bonferroni post hoc analysis for the main effect. In the bar graph, means with the same letter are not significantly different. This graph is titled "Detection and Recognition Distances by VES for the Snow Condition." The Y-axis shows the mean distance in feet. The X-axis includes the four VESs: five UV-A + HLB, hybrid UV-A + HLB, HLB, and HID. There are two bars for each VES, one for detection distance and one for recognition distance. Letters above each bar note the groupings for the means (same letters are not significantly different) based on the Bonferroni results. Each bar has a standard error bar at its top. Detection and recognition distances range from about 217 feet (five UV-A + HLB) to 168 feet (HID). For detection distance, five UV-A + HLB and hybrid UV-A + HLB are statistically grouped, as are hybrid UV-A + HLB and HLB. Recognition distances are about 15 to 20 feet lower for all VESs; five UV-A + HLB, hybrid UV-A + HLB and HLB are statistically grouped. All standard errors are about 9 feet. Back to Figure 9.

Figure 10. Bar graph. Bonferroni post hoc results on detection and recognition distances for the main effect: object. This bar graph shows a comparison of the three objects in a Bonferroni post hoc analysis for the object main effect. The graph is titled "Detection and Recognition Distances by Object for the Snow Condition." The Y-axis shows the mean distance in feet. The X-axis includes the three objects evaluated in the study. There are two bars for each object, one for detection distance and one for recognition distance. Letters above each bar note the groupings for the means (same letters are not significantly different) based on the Bonferroni results. Each bar has a standard error bar at its top. The perpendicular and parallel pedestrians in white clothing are statistically grouped for both detection distance (about 228 feet) and recognition distance (about 212 feet). The perpendicular pedestrian in black clothing has significantly lower distances, about 131 feet for detection and 118 feet for recognition. All standard errors are about 6 feet.
Back to Figure 10.

Figure 11. Equation. Braking distance. Lowercase d subscript BD equals uppercase V squared divided by the following: the sum of lowercase f and uppercase G, end of sum, that sum multiplied by lowercase g, multiplied by 2. Back to Figure 11.

Figure 12. Equation. Total stopping distance for brake reaction time plus braking distance. Lowercase d equals the following sum: 2.5 multiplied by uppercase V, plus the quotient of uppercase V squared divided by a denominator of 2 multiplied by lowercase g multiplied by lowercase f. Back to Figure 12.

Figure 13. Equation. AASHTO calculation of coefficient of friction for wet pavement. Lowercase f equals lowercase a divided by lowercase g, which equals 11.2 feet per second squared divided by 32.2 feet per second squared, which equals a friction coefficient of 0.35. Back to Figure 13.

Figure 14. Bar graph. Participants' visual acuity divided by age group. The Y-axis shows the number of participants from 0 to 7. The X-axis shows visual acuity from 20/13 to 20/40. One style of bar represents young participants, and another represents middle-aged participants. Young participants are grouped between 20/13 and 20/25, tending toward a peak at 20/20. Middle-aged participants are spread evenly from 20/15 to 20/40 except for a spike at 20/20. Back to Figure 14.

Figure 15. Bar graph. Participants' contrast sensitivity at 1.5 cycles per degree (cpd) divided by age group. The Y-axis is labeled "Number of Participants," and the scale starts at 0 and ends at 7. The X-axis is labeled "Percentage of Contrast at 1.5 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 0.59 (Good) to 5 (Poor). One style of bar represents young participants, and another represents middle-aged participants. For the left eye, young participants are bunched between 0.83 and 2.86, which is the middle of the total range. Middle-aged participants are spread more evenly between 0.83 and 5 (Poor). For the right eye, all participants are grouped between 1.43 and 2.86. Back to Figure 15.

Figure 16. Bar graph. Participants' contrast sensitivity at 3.0 cpd divided by age group. The Y-axis is labeled "Number of Participants," and the scale starts at 0 and ends at 7. The X-axis is labeled "Percentage of Contrast at 3.0 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 ranges from 0.45 (Good) to 4.17 (Poor). One style of bar represents young participants, and another represents middle-aged participants. For the left eye, all participants are grouped between 0.45 (Good) and 2.27, with a tendency toward the better end of the scale, slightly more so for young participants. For the right eye, all participants are grouped between 0.45 (Good) and 1.13 with a tendency toward the worse end of that range. Back to Figure 16.

Figure 17. Bar graph. Participants' contrast sensitivity at 6.0 cpd divided by age group. The Y-axis is labeled "Number of Participants," and the scale starts at 0 and ends at 7. The X-axis is labeled "Percentage of Contrast at 6.0 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 ranges from 0.38 (Good) to 4.76 (Poor). One style of bar represents young participants, and another represents middle-aged participants. For the left eye, all participants ranged between 0.54 and 4.76 (Poor) with a tendency toward the better end of the scale. The lone score of 4.76 (Poor) belonged to one middle-aged participant, and the only two scores of 2.22 belonged to two young participants. For the right eye, young participants ranged from 0.38 (Good) to 2.22, and middle-aged participants ranged from 0.54 to 2.22; all participants tended toward the middle, 0.8. Back to Figure 17.

Figure 18. Bar graph. Participants' contrast sensitivity at 12.0 cpd divided by age group. The Y-axis is labeled "Number of Participants," and the scale starts at 0 and ends at 7. The X-axis is labeled "Percentage of Contrast at 12.0 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 between 0.59 (Good) and 12.5 (Poor). One style of bar represents young participants, and another represents middle-aged participants. For the left eye, scores ranged between the two extremes, 0.59 (Good) and 12.5 (Poor), with a tendency toward the range of 1.14 to 1.82. Young participants show slightly better contrast sensitivity than middle-aged participants. For the right eye, scores ranged from 0.8 to 12.5 (Poor) with no scores at 3.13. Again, there is a tendency toward the range of 1.14 to 1.82, and young participants show slightly better contrast sensitivity than middle-aged participants, though only by one more participant at 0.8 and one fewer at 1.82. Back to Figure 18.

Figure 19. Bar graph. Participants' contrast sensitivity at 18.0 cpd divided by age group. The Y-axis is labeled "Number of Participants," and the scale starts at 0 and ends at 7. 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). One style of bar represents young participants, and another represents middle-aged participants. For the left eye, young participants ranged between 2.5 and 10 with a strong tendency toward the better end of that range. Middle-aged participants were distributed more evenly between 2.5 and 25 (Poor). For the right eye, all participants were distributed between 2.5 and 25 (Poor) with a tendency toward the better end of that range. Back to Figure 19.

Appendix C. Contrast sensitivity test diagram for participants. The diagram shows the form the experimenters used to document the results for each participant's contrast sensitivity exam. There are two diagrams, one for recording the results of the right eye and one for the results of the left eye. Each diagram shows a graph with contrast sensitivity from 3 to 300 on the left Y-axis, contrast threshold from 0.0 to 0.003 on the right Y-axis, and spatial frequency (cycles per degree) from 0.5 to 6 on the X-axis. There is a column of circles above each cycle per degree. The experimenter documents the participant's response by filling in the appropriate circle. Back to Diagram.

Figure 20. Photo. Aerial view of the Virginia Smart Road. The photograph shows a paved road with a large turnaround at one end extending down into a valley at the other end. The area appears to be mostly rural. Back to Figure 20.

Appendix J. Hotspot location. 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." Back to Diagram.