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Publication Number: FHWA-HRT-04-140
Date: December 2005

Enhanced Night Visibility Series, Volume IX: Phase II—Characterization of Experimental Objects

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Figure 1. Diagram. Object stations (locations) on the Virginia Smart Road. 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 labeled “Top Turnaround - Entrance” and 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” located approximately one-third and two-thirds of the way down the road. A legend contains an arrow labeled “Object Location.” There are six arrows along the side of the road indicating the six locations where the objects were presented. Locations 1, 2, and 3 are on one side of the road, indicating that a driver would see objects at these locations during the drive from the top to the bottom of the road. Locations 4, 5, and 6 are on the opposite side of the road indicating that a driver would see these objects during the drive from the bottom of the road to the top of the road. Locations 1, 2, 4, and 5 are all grouped towards 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. Location 3 is located just before the turnaround labeled “Turnaround 3.” Location 6 is located opposite the turnaround labeled “Turnaround 2.” Back to Figure 1.

Figure 2. Illustration. Parallel pedestrian measurement points. The diagram shows the front view of a person wearing white scrubs and standing with feet together and arms down to the side. Thirteen different measurement points are indicated by the placement of numbers at various locations. The numbers and corresponding locations are as follows: 1, the face; 2, the chest; 3, the waist; 4, the left (from viewer’s prospective) shin; 5, the right (from viewer’s prospective) shin; 6, below the feet; 7, to the left of the left shin; 8, to the right of the right shin; 9, to the left of the waist; 10, to the right of the waist; 11, to the left of the chest; 12, to the right of the chest; and 13, above the head. Back to Figure 2.

Figure 3. Illustration. Perpendicular pedestrian measurement points. The diagram shows the side view of a person wearing white scrubs and standing with feet together and arms down to the side. Thirteen different measurement points are indicated by the placement of numbers at various locations. The numbers and corresponding locations are as follows: 1, the head; 2, the upper arm; 3, the abdomen; 4, the thigh; 5, the shin; 6, below the feet; 7, to the left (from viewer’s perspective) of the shin; 8, to the right (from viewer’s perspective) of the shin; 9, to the left of the abdomen; 10, to the right of the abdomen; 11, to the left of the chest; 12, to the right of the chest; and 13, above the head. Back to Figure 3.

Figure 4. Illustration. Cyclist measurement points. The diagram shows the side view of a person riding a bike. Fourteen different measurement points are indicated by the placement of numbers at various locations. The numbers and corresponding locations are as follows: 1, the shoulder; 2, the waist; 3, the knee; 4, the ankle; 5, beneath the front wheel; 6, beneath the rear wheel; 7 the midpoint between locations 5 and 6; 8, in front of the front wheel (to the left of the front wheel from viewer’s perspective); 9, behind the rear wheel (to the right of the rear wheel from viewer’s perspective); 10, above the front wheel; 11, above the rear wheel; 12, in front of the head (to the left of the head from viewer’s perspective); 13, behind the upper back (to the right of the upper back from viewer’s perspective); and 14, above the head. Back to Figure 4.

Figure 5. Illustration. Child’s bicycle measurement points. The diagram shows a child’s bicycle on its side with the back wheel parallel to the ground and the front wheel perpendicular to the ground, wheels toward the observer. Six different measurement points are indicated by the placement of numbers at various locations. The numbers and corresponding locations are as follows: 1, the bike frame just below the handle bars; 2, the chain ring; 3, above the handlebars; 4, in front of the front wheel (to the left of the front wheel from viewer’s perspective); 5, behind the rear wheel (to the right of the rear wheel from viewer’s perspective); and 6, on the ground below the chain wheel. Back to Figure 5.

Figure 6. Illustration. Tire tread measurement points. The diagram shows an intact circular tire tread lying on its side. Five different measurement points are indicated by the placement of numbers at various locations. The numbers and corresponding locations are as follows: 1, center of the tire tread surface; 2, above the tire tread; 3, to the left (from viewer’s perspective) of the tire tread; 4, to the right of (from viewer’s perspective) the tire tread; and 5, beneath the tire tread. Back to Figure 6.

Figure 7. Bar graph. Comparison of the mean of background object luminance for HLB combined with different UV–A levels when the photometer operator is in the back seat or the driver’s seat. The graph is titled “Back Seat and Driver’s Seat Photometer Operator Position Comparison by UV Type.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “UV Type,” and the following categories of UV–A are listed along it: none, three UV–A, and five UV–A. There are two bars for each UV–A category, one for back seat and one for driver’s seat. Standard error bars are present for each bar. Luminance for the back seat position ranges from approximately 0.076 for no UV–A to 0.092 for three UV–A. Luminance for the driver’s seat position ranges from approximately 0.062 for no UV–A to 0.095 for five UV–A. Standard errors are nearly all plus or minus 0.025 except for no UV–A from the driver’s seat, which has a standard error of approximately 0.012. Back to Figure 7.

Figure 8. Bar graph. Comparison of object luminance for HLB combined with different UV–A levels when the photometer operator is in the back seat or the driver’s seat. The graph is titled “Back Seat and Driver’s Seat Photometer Operator Position Comparison of Object Luminance by UV Type.” The Y-axis is labeled “Object Luminance (candela per square meter).” The X-axis is labeled “UV Type,” and the following categories of UV–A are listed along it: none, three UV–A, and five UV–A. There are two bars for each UV–A category, one for back seat and one for driver’s seat. Standard error bars are present for each bar. Luminance for the back seat position ranges from approximately 0.18 for no UV–A to 0.23 for three UV–A. Luminance for the driver’s seat position ranges from approximately 0.13 for no UV–A to 0.23 for five UV–A. Standard errors range from plus or minus 0.008 for no UV–A from the driver’s seat to plus or minus 0.06 for five UV–A from the back seat; standard errors clearly do not overlap only for no UV–A. Back to Figure 8.

Figure 9. Equation. Lambertian reflection. Rho equals uppercase L multiplied by pi, that product divided by uppercase E. Back to Figure 9.

Figure 10. Equation. Specular reflection. Rho equals uppercase L divided by uppercase E. Back to Figure 10.

Figure 11. Equation. Object fluorescence. Percent Fluorescence equals the quotient of rho subscript Fluorescent divided by rho subscript Non-fluorescent, that quotient multiplied by 100. Back to Figure 11.

Figure 12. Equation. Contrast ratio. C equals uppercase L subscript Object minus uppercase L subscript Background, that difference divided by uppercase L subscript Background. Back to Figure 12.

Figure 13. Equation. Basic delta uppercase L subscript lowercase th model. Luminance difference subscript lowercase th equals lowercase k times the following sum squared: the quotient of phi to the one-half power divided by alpha, that quotient plus uppercase L to the one-half power. Back to Figure 13.

Figure 14. Equation. Time factor for the delta uppercase L subscript lowercase th model. Uppercase TF equals the quotient of the following: the sum of function lowercase a of alpha and uppercase L subscript uppercase B, that function plus lowercase t, that sum divided by lowercase t. Back to Figure 14.

Figure 15. Equation. Age factor for the delta uppercase L subscript lowercase th model. Uppercase AF equals the following: Age minus lowercase a, that difference squared, that product divided by lowercase b, that quotient plus lowercase c. Back to Figure 15.

Figure 16. Equation. Complete delta uppercase L subscript lowercase th model. Luminance difference subscript lowercase th equals lowercase k multiplied by the following sum squared: the quotient of phi to the one-half power divided by alpha, that quotient plus uppercase L to the one-half power. That sum squared multiplied by lowecase k, uppercase TF, uppercase F subscript uppercase CP, and uppercase AF.
Back to Figure 16.

Figure 17. Equation. Visibility level. Uppercase VL equals the quotient of delta uppercase L subscript Actual divided by delta uppercase L subscript Threshold, which is equal to the quotient of the difference of uppercase L subscript Object minus uppercase L subscript Background, that difference divided by delta uppercase L subscript Threshold, which is equal to the quotient of uppercase C subscript Actual divided by uppercase C subscript Threshold. Back to Figure 17.

Figure 18. Bar graph. Object illuminance by UV–A level. The graph is titled “Illuminance of Objects by Location and UV Level.” The Y-axis is labeled “Illuminance (lux).” The X-axis is labeled “UV Level” and is broken into the following four levels of UV: none, hybrid UV–A, three UV–A, and five UV–A. Each UV–A category has three bars representing the cyclist, perpendicular pedestrian, and parallel pedestrian. Standard error bars are present for each bar. For the cyclist, the illuminance ranges from approximately 5.7 lux with no UV–A to 7 lux with five UV–A, though hybrid UV–A and three UV–A are nearly as high. For the perpendicular pedestrian, the illuminance ranges from approximately 5.1 lux with no UV–A to 6.5 lux with hybrid, three, and five UV–A. For the parallel pedestrian, the illuminance ranges from approximately 6.9 lux and 7.2 lux with no UV–A and hybrid UV–A, respectively, to 8.8 lux with three UV–A and five UV–A. Standard errors are comparable, ranging from plus or minus 0.5 lux with no UV–A and the parallel pedestrian to plus or minus 1.2 lux with three UV–A and the perpendicular pedestrian. Back to Figure 18.

Figure 19. Bar graph. Illuminance from each VES by measurement height for the pedestrian object types. The graph is titled “Illuminance of VESs by Measurement Height.” The X-axis is labeled “Illuminance (lx).” The Y-axis is labeled “Measurement Height” and is divided into four categories: chest, waist, knee, and ankle. There are five types of bars for each measurement height that represent the following VESs: HLB, HID, HHB, HOH, and HLB–LP. Standard errors are noted for each bar. HLB illuminance ranges from 6 (chest) to 9 (knee). HID illuminance ranges from 2 (chest) to just over 5 (ankle). HHB illuminance ranges from 10 (ankle) to 18 (waist). HOH illuminance ranges from 2 (chest) to just over 10 (ankle). HLB–LP illuminance ranges from 5.5 (chest) to 6.5 (knee). Standard errors are roughly comparable. Back to Figure 19.

Figure 20. Bar graph. Illuminance from each VES by object position for the pedestrian object types. The graph is titled “Illuminance of Pedestrian Types by VES.” The Y-axis is labeled “Illuminance (lux),” and the X-axis is labeled “VES.” The five VESs (HLB, HID, HHB, HOH, and HLB–LP) are listed across the X-axis, and there are three bars for each VES that represent the illuminance of the cyclist, perpendicular pedestrian, and parallel pedestrian. Standard error bars are on top of each bar. Illuminance ranged from 2.9 (HID) to 15.1 (HHB) for the cyclist, 2.5 (HID) to 14.9 (HHB) for the perpendicular pedestrian, and 6.1 (HID) to 12.1 (HHB) for the parallel pedestrian. Illuminance values for HLB were generally comparable across objects, ranging between approximately 7.9 (parallel pedestrian) and 8.7 (cyclist). Illuminance values for HOH ranged from approximately 4.2 (perpendicular pedestrian) to 7.5 (parallel pedestrian). HLB–LP ranged from approximately 5.9 (perpendicular pedestrian) to 6.1 (parallel pedestrian). The standard error varied, with HLB–LP generally producing the smallest standard error of approximately plus or minus 0.5 and HOH producing the largest standard error of approximately plus or minus 1.0. Back to Figure 20.

Figure 21. Bar graph. Illuminance and distance relationship by lamp and measurement location with the inverse square law trends for the pedestrian object types. The graph is titled “Illuminance of Parallel and Perpendicular Pedestrians by Measurement Height, VES, and Distance.” The Y-axis is labeled “Illuminance (lux).” The X-axis is labeled “Distance (unit: feet)” and is broken into the following four categories: 200 feet, 300 feet, 500 feet, and 800 feet. There are four bars in each category that represent one of the following: HLB chest, HLB waist, HID chest, and HID waist. Standard errors are noted for each bar. Illuminance ranges from 0.8 (800 feet) to 6 (200 feet) for HLB chest, 0.8 (800 feet) to 9.8 (200 feet) for HLB waist, 0.4 (800 feet) to 1.8 (200 feet) for HID chest, and 0.5 (800 feet) to 4 (200 feet) for HID waist. The standard errors produced at 200 feet are the largest, and standard errors get smaller as the distance increases. The graph has a line labeled “Inverse Square-HLB.” The following are approximate coordinates along the curve: 200 feet at 10 lux, 300 feet at 4.1 lux, 500 feet at 1.7 lux, and 800 feet at 0.5 lux. This curve follows the illuminance of the HLB waist. The graph has another line labeled “Inverse Square-HID.” The following are approximate coordinates along this curve: 200 feet at 7.1 lux, 300 feet at 3.1 lux, 500 feet at 1.2 lux, and 800 feet at 0.4 lux. Back to Figure 21.

Figure 22. Bar graph. Illuminance on the child’s bicycle and the tire tread for each VES type. The title of the graph is “Illuminance of the Tire Tread and Child’s Bicycle by VES.” The Y-axis is labeled “Illuminance (lux).” The X-axis is labeled “VES.” Five VESs-HLB, HID, HHB, HOH, and HLB–LP-are listed across the X-axis, and there are two bars for each VES representing the illuminance of the child’s bicycle and the illuminance of the tire tread. Standard error bars are present at the top of each bar. The illuminance of the child’s bicycle ranges from approximately 6 lux with HLB–LP to 10.9 lux with HOH. Illuminance of the tire tread ranges from approximately 6 lux with HLB–LP to 12.5 lux with HLB. There are noticeable differences between the illuminance of the two objects with the HLB configuration. The child’s bicycle was approximately 8.9 lux with HLB compared to the tire tread which was approximately 12.5 lux. HID also produced noticeable differences, with approximate illuminances of 6.5 and 9.5 for the child’s bicycle and tire tread, respectively. The HID configuration produced the smallest standard error, and the HHB and HOH configurations produced the largest standard error. Back to Figure 22.

Figure 23. Bar graph. Object luminance by VES for white- and black-clothed pedestrians. The graph is titled “Pedestrian Object Luminance by Clothing Color and VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are two bars for each VES; one bar represents the luminance of white-clothed pedestrians and one bar represents the luminance of black-clothed pedestrians. Standard error bars are present at the top of each bar. The luminance of pedestrians in black ranges from approximately 0.05 (HID) to 0.1 (HHB). For the pedestrian dressed in white, the graph shows that as the level of UV–A increases, the luminance also increases. The luminance of the white-clothed pedestrian with HLB alone is approximately 1.25 as compared to approximately 3.1 with five UV–A plus HLB. The luminance of the white pedestrian with HID alone is approximately 0.75. This increases to approximately 1.9 with five UV–A plus HLB. The standard error is the generally comparable across the VESs.
Back to Figure 23.

Figure 24. Bar graph. Object luminance by VES for black-clothed pedestrians and cyclist by object position. The graph is titled “Luminance of Black-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the luminance of the cyclist, perpendicular pedestrian, and parallel pedestrian. Illuminance ranges from 0.03 (HID) to 0.115 (HHB) for the cyclist, 0.038 (HID) to 0.121 (HHB) for the perpendicular pedestrian, and 0.055 (HLB–LP) to 0.098 (HHB) for the parallel pedestrian. In general, the luminance for all objects with HLB configurations (with the exception of HLB–LP) was higher than with the HID configurations. HLB configurations range from 0.07 (HLB paired with perpendicular pedestrian) to 0.091 (five UV–A plus HLB paired with all three objects and three UV–A plus HLB paired with the parallel pedestrian and the cyclist). HID configurations range from 0.03 (HID paired with cyclist) to 0.076 (three UV–A plus HID paired with cyclist). The standard errors are generally comparable with a few exceptions. Three UV–A plus HID paired with the cyclist produced a noticeably larger standard error of approximately plus or minus 0.045. HOH and HHB both produced larger standard errors for all objects of approximately plus or minus 0.015. Back to Figure 24.

Figure 25. Bar graph. Object luminance by VES for black-clothed perpendicular pedestrians by measurement height. The graph is titled “Luminance of the Black-Clothed Perpendicular Pedestrian by Measurement Height and VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following measurement heights: chest, waist, knee and ankle. Luminance ranges from 0.013 (HID) to 0.14 (HHB) for the chest, 0.03 (both hybrid UV–A plus HID and three UV–A plus HID) to 0.15 (HHB) for the waist, 0.045 (hybrid UV–A plus HID) to 0.107 (HHB) for the knee, and 0.045 (HID) to 0.097 (both three UV–A plus HLB and five UV–A plus HLB) for the ankle. In general the HLB configurations (with the exception of HLB–LP), produced larger luminance at all measurement heights than the HID configurations. In general the smallest luminance is at chest height. The HLB and hybrid UV–A plus HLB are an exception to this with all the measurement heights falling between approximately 0.065 and 0.078, and standard errors of approximately plus or minus 0.02. HHB is also an exception with a luminance of approximately 0.14 for chest height and smaller values for knee and ankle (0.105 and 0.089 respectively). Standard errors vary, with HOH producing noticeably larger standard errors for the waist, knee, and ankle heights. Back to Figure 25.

Figure 26. Bar graph. Object luminance by VES for white-clothed pedestrians by object position. The graph is titled “Luminance of the White-Clothed Pedestrian by Pedestrian Type and VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the cyclist, perpendicular pedestrian, and parallel pedestrian. The graph shows the effect that UV–A level has on the HLB and HID VESs. For the HLB configurations, luminance levels increase as the level of UV–A increases. The graph shows the following approximate range of luminance for the pedestrian types when paired with the different HLB configurations: 1.25 (HLB) to 3.3 (five UV–A plus HLB) for the cyclist, 1.2 (HLB) to 2.4 (five UV–A plus HLB) for the perpendicular pedestrian, and 1.4 (HLB) to 3.6 (five UV–A plus HLB) for the parallel pedestrian. The graph shows the following approximate range of luminance for the pedestrian types when paired with the different HID configurations: 0.5 (HID) to 1.8 (five UV–A plus HID) for the cyclist, 0.6 (HID) to 2.2 (five UV–A plus HID) for the perpendicular pedestrian, and 1.25 (HID) to 1.7 (five UV–A plus HID) for the parallel pedestrian. Luminance values for all pedestrian types paired with HLB–LP or HOH range between about 0.75 and 1.1. Luminance values for HHB range from about 1.8 (parallel pedestrian) to 2.25 (perpendicular pedestrian). The standard errors are generally comparable. The five UV–A combined with both HLB and HID produced larger standard errors for all objects, as did the three UV–A plus HLB and the cyclist and parallel pedestrian. Back to Figure 26.

Figure 27. Bar graph. Object luminance by VES for white-clothed perpendicular pedestrian by measurement height. The graph is titled “Luminance of the White-Clothed Perpendicular Pedestrian by Measurement Height and VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the measurements taken at the following heights: chest, waist, knee, and ankle. The graph shows the following approximate range of luminance for the measurement heights when paired with the different HLB configurations: 1 (HLB and hybrid plus HLB) to 2.1 (five UV–A plus HLB) for the chest, 1.4 (HLB) to 2.75 (five UV–A plus HLB) for the waist, 1.25 (HLB) to 2.75 (five UV–A plus HLB) for the knee, and 1.1 (HLB) to 2.1 (five UV–A plus HLB) for the ankle. The graph shows the following approximate range of luminance for the measurement heights when paired with the different HID configurations: 0.25 (HID) to 1.3 (five UV–A plus HID) for the chest, 0.6 (HID) to 2.4 (five UV–A plus HID) for the waist, 0.9 (HID) to 2.5 (five UV–A plus HID) for the knee, and 0.8 (HID) to 2.4 (five UV–A plus HID) for the ankle. The approximate range of luminance for the different measurement heights with HHB was 1.5 (ankle) to 2.9 (waist). The approximate range of luminance for the different measurement heights with HOH was 0.2 (chest) to 1.1 (ankle). The luminance for all measurement heights with HLB–LP ranged from about 0.4 to 1, with the standard error bars appearing to overlap all heights. The standard error bars on the graph vary. HID produced the smallest standard error across measurement heights. The following combination produced noticeably large standard errors of at least plus or minus 1: HLB and waist, five UV–A plus HLB and knee, hybrid UV–A plus HID and knee, and HOH paired with knee and ankle.
Back to Figure 27.

Figure 28. Bar graph. Object luminance by VES for white-clothed pedestrians by measurement distance. The graph is titled “Luminance for White-Clothed Pedestrian for Distance by VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following measurement distances: 200 feet, 300 feet, 500 feet, and 800 feet. The graph shows the following approximate range of luminance for the measurement distances when paired with the different HLB configurations: 1.3 (HLB) to 3.0 (five UV–A plus HLB) at 200 feet, 0.6 (HLB) to 1.0 (five UV–A plus HLB) at 300 feet, 0.2 (HLB and hybrid UV–A plus HLB) to 0.3 (three UV–A plus HLB and five UV–A plus HLB) at 500 feet, and luminance values are indistinguishable between the VESs at 800 feet, appearing to fall between 0.05 and 0.1. The graph shows the following approximate range of luminance for the measurement distances when paired with the different HID configurations: 0.9 (HID) to 1.9 (five UV–A plus HID) at 200 feet, 0.25 (HID) to 0.6 (five UV–A plus HID) at 300 feet, 0.1 (HID) to 0.2 (five UV–A plus HID) at 500 feet, and luminance values are indistinguishable between the VESs at 800 feet, appearing to fall between 0.05 and 0.1. The range for HOH and HLB–LP configurations at 800 feet are similar to the other VESs, less than 0.05, and the luminance at 200 feet is approximately 0.8. The range for HHB is about 0.05 at 800 feet to 2.2 at 200 feet. Standard errors are generally comparable, with five UV–A plus HLB producing a slightly larger standard error. Back to Figure 28.

Figure 29. Bar graph. Object luminance by VES for the child’s bicycle. The graph is titled “Luminance for Child’s Bicycle by VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There is one bar for each VES that represents the luminance. Standard error bars are atop each bar. Luminance for the HLB configurations ranges from approximately 0.55 (HLB) to 1.4 (five UV–A plus HLB). Luminance for the HID configurations ranges from approximately 0.5 (HID) to 1.9 (five UV–A plus HID). The luminance for HHB is approximately 0.4, and the luminance for HOH is approximately 0.75. HLB–LP has the lowest luminance of all the VESs at about 0.25, and it also produced the smallest standard error. HLB paired with the hybrid UV–A and the five UV–A produced the largest standard error. Back to Figure 29.

Figure 30. Bar graph. Object luminance by VES for the tire tread. The graph is titled “Luminance of Tire Tread by VES.” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There is one bar for each VES that represents the luminance. Standard error bars are atop each bar. Luminance for the HLB configurations ranges from approximately 0.09 (HLB) to 0.19 (three UV–A plus HLB). Luminance for the HID configurations ranges from approximately 0.09 (HID) to 0.125 (hybrid UV–A plus HID). The luminance for HHB is approximately 0.125, and the luminance for HOH is approximately 0.14. HLB–LP has the lowest luminance of all the VESs at about 0.075. In general, the HLB combinations and HHB produced larger standard errors than the other VESs. Back to Figure 30.

Figure 31. Bar graph. Object luminance by VES for the cyclists’ bicycles. The graph is titled “Luminance of Cyclist’s Bicycle for Pedestrian Clothing Color by VES” The Y-axis is labeled “Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are two bars for each VES; one bar represents the dark bicycle and the other bar represents the light bicycle. Standard error bars are atop each bar. The following are the approximate ranges of luminance for the HLB configurations. Dark bicycle: 1.2 (HLB) to 5.8 (five UV–A plus HLB). Light bicycle: 0.8 (HLB) to 2.2 (five UV–A plus HLB). The following are the approximate ranges of luminance for the HID configurations. Dark bicycle: 1.0 (three UV–A plus HID and five UV–A plus HID) to 1.6 (hybrid UV–A plus HID). Light bicycle: 0.4 (HID) to 1.4 (five UV–A plus HID). Luminance values with HHB are approximately 3.4 and 1.0 for the dark and light bicycle, respectively. Luminance values with HOH are approximately 2.5 and 0.3 for the dark and light bicycle, respectively. Luminance values with HLB–LP are approximately 1.0 and 0.4 for the dark and light bicycle, respectively. The dark bicycle produced larger standard errors overall, particularly when paired with the HLB configurations. Back to Figure 31.

Figure 32. Bar graph. Background luminance for white- and black-clothed pedestrians by UV–A based VES. The graph is titled “Pedestrian Background Luminance for Black- and White-Clothed Pedestrians by VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are two bars for each VES that represent black-clothed objects and white-clothed objects. Standard error bars are present for each bar. White-clothed objects show greater background luminance for all VESs that use UV–A, though standard errors overlap for all VESs. Background luminance for the HLB-based VESs, especially for three UV–A plus HLB and five UV–A plus HLB, are greater than that of the HID-based VESs. Background luminance for the black-clothed objects ranges from approximately 0.049 candela per square meter for five UV–A plus HID to 0.075 candela per square meter for three UV–A plus HLB and five UV–A plus HLB. Background luminance for the white-clothed objects ranges from approximately 0.049 candela per square meter for the HID to 0.085 candela per square meter with five UV–A plus HLB. Standard errors range from plus or minus 0.01 candela per square meter for HLB with black- and white-clothed objects to plus or minus 0.02 for five UV–A plus HLB with white-clothed objects. Back to Figure 32.

Figure 33. Bar graph. Influence of VES on background luminance by pedestrian position. The graph is titled “Pedestrian Background Luminance for Pedestrian Type by VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed along the X-axis: HLB, HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the cyclist, the perpendicular pedestrian, and the parallel pedestrian. Standard error bars are atop each bar. The following are the approximate ranges of background luminance for the pedestrian types. Cyclist: 0.04 (HID and HLB–LP) to 0.08 (HOH). Perpendicular: 0.04 (HLB–LP) to 0.1 (HHB). Parallel: 0.04 (HLB–LP) to 0.18 (HOH-note that this has a standard error of plus or minus 0.1). The graph shows that the background luminance for the three different pedestrian types is similar within each VES. Back to Figure 33.

Figure 34. Bar graph. Influence of VES on background luminance by measurement height. The graph is titled “Background Luminance of Pedestrian Types by VES and Measurement Height.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “Measurement Height,” and the following measurement heights are listed along the X-axis: Chest, Waist, Knee, and Ankle. There are five bars for each measurement height, and each bar represents one of the following VESs: HLB, HID, HHB, HOH, and HLB–LP. Standard error bars are atop each bar. Background luminance for the chest height measurement ranged from about 0.02 and 0.03 for the different VESs. Background luminance for the waist height measurement ranged from about 0.03 (HID and HLB–LP) to 0.05 (HLB and HHB). Background luminance for the knee height measurement ranged from about 0.05 (HLB–LP) to 0.15 (HHB). Note that the standard error for the HHB knee height measurement was noticeably larger than other standard errors at about plus or minus 0.05. Background luminance for the ankle height measurement ranged from about 1.2 (HLB–LP) to 0.42 (HOH). Note that the standard error for HOH was noticeably larger than other standard errors at about plus or minus 0.18. Back to Figure 34.

Figure 35. Bar graph. Influence of VES on background luminance by pedestrian type and measurement height. The graph is titled “Pedestrian Background Luminance for VES Type by Pedestrian Type and Measurement Height.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “Pedestrian Type and Measurement Height.” The X-axis is broken into three large categories: cyclist, perpendicular pedestrian, and parallel pedestrian. Each of these categories is further broken down into the following measurement heights: face, chest, waist, knee, and ankle. There are five bars for each measurement height, and each bar represents one of the following VESs: HLB, HID, HHB, HOH, and HLB–LP. Standard error bars are atop each bar. Background luminance appears to increase as the measurement height gets closer to the ground. The differences between the luminance values for face and chest measurements across the VES and pedestrian types are indistinguishable on this graph. They appear to generally fall between 0.02 and 0.04. The luminance values for the waist are also indistinguishable from one another, but do appear to be slightly higher at about 0.05 to 0.07. The luminance values for the knee generally appear to be between 0.07 and 0.1 with the exception of the measurement height combined with the HHB and perpendicular pedestrian which is approximately 0.202 (note that the corresponding standard error is approximately plus or minus 0.1). The background luminance for the ankle height measurements generally fall between 0.1 and 0.29. Two noticeable exceptions are the ankle height measurements for HHB and HOH when each is paired with the parallel pedestrian. The background luminance with these two VESs is approximately 0.38 and 0.72 respectively. The standard error for these two are noticeably larger at approximately plus or minus 0.2 for HHB and plus or minus 0.5 for HOH. Back to Figure 35.

Figure 36. Bar graph. Influence of VES on background luminance by measurement distance. The graph is titled “Background Luminance of Pedestrian Types by VES and Distance.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “Distance (unit: feet).” The following distances are listed along the X-axis: 200 feet, 300 feet, 500 feet, and 800 feet. There are five bars for each measurement height; each bar represents one of the following VESs: HLB, HID, HHB, HOH, and HLB–LP. Standard error bars are atop each bar. There is a noticeably larger range of background luminance for the measurements taken at 200 feet than for the other distances. The approximate background luminances at 200 feet are as follows: 0.04 (HLB–LP), 0.05 (HID), 0.06 (HLB), 0.11 (HHB), and 0.14 (HOH). The standard errors produced by the HHB and HOH are noticeably larger at approximately plus or minus 0.05 and plus or minus 0.07, respectively. The approximate ranges of background luminance for the other distances follow. At 300 feet: 0.035 (HLB–LP) to 0.045 (HOH), and all the standard error bars appear to overlap. At 500 feet: 0.02 (HLB) to 0.025 (HLB–LP), and all the standard error bars appear to overlap. At 800 feet: 0.02 (HOH) to 0.025 (HID), and all the standard error bars appear to overlap. A line labeled “Inverse Square” has been added to the bar graph. It has the following approximate coordinates: (200 feet, 0.07), (300 feet, 0.03), (500 feet, 0.015), (800 feet, 0.001). Back to Figure 36.

Figure 37. Bar graph. Influence of station on background luminance for pedestrians by VES. The graph is titled “Background Luminance of Pedestrian Types by VES and Station.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “station” and lists stations one through five. There are five bars for each measurement height; each bar represents one of the following VESs: HLB, HID, HHB, HOH, and HLB–LP. Standard error bars are atop each bar. The approximate ranges of background luminance for the individual stations are as follows: station 1: 0.04 (HLB–LP and HID) to 0.09 (HHB). station 2: 0.035 (HLB–LP and HOH) to 0.08 (HHB). station 3: 0.04 (HID) to 0.125 (HLB). station 4: 0.05 (HLB–LP) to 0.24 (HOH). station 5: 0.05 (HLB–LP) to 0.075 (HID). Standard errors were generally comparable with a few exceptions. The following combinations produced noticeably larger standard errors: HHB and station 2, HHB and station 3, HHB and station 4, HLB and station 3, HOH and station 4. Back to Figure 37.

Figure 38. Bar graph. Influence of measurement height on background luminance of child’s bicycle by VES. The graph is titled “Background Luminance of Child’s Bicycle by Measurement Height and VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed: HLB, HID, HHB, HOH, and HLB–LP. There are three bars for each VES representing the Bottom, Middle, and Top measurement heights. Standard error bars are atop each bar. The following are the approximate ranges of background luminance for the different measurement heights. Bottom: 0.11 (HLB–LP) to 0.21 (HOH). Middle: 0.06 (HLB–LP) to 0.13 (HOH). Top: 0.035 (HLB–LP) to 0.075 (HOH). The measurements at the bottom height produced noticeably larger standard errors.
Back to Figure 38.

Figure 39. Bar graph. Influence of station on background luminance for the child’s bicycle by VES. The graph is titled “Background Luminance of the Child’s Bicycle by Station and VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed: HLB, HID, HHB, HOH, and HLB–LP. There are five bars for each VES; each bar represents a specific station and is labeled accordingly as station 1, station 2, station 4, station 5, or station 6. Standard error bars are atop each bar. The following are the approximate ranges of background luminance. Station 1: 0.05 (HID) to 0.14 (HOH). station 2: 0.06 (HLB–LP) to 0.12 (HOH). station 4: 0.08 (HHB and HLB) to 0.175 (HOH). station 5: 0.055 (HLB–LP and HHB) to 0.11 (HLB and HOH). Station 6: 0.06 (HLB–LP) to 0.16 (HLB). The standard errors are generally comparable at about plus or minus 0.05 with a few exceptions. The following combinations produced noticeably smaller standard errors: HID paired with station 1 and HLB–LP paired with station 5. HOH paired with station 4 produced a noticeably larger standard error. Back to Figure 39.

Figure 40. Bar graph. Influence of measurement height on background luminance for the tire tread by VES. The graph is titled “Background Luminance of Tire Tread by Measurement Height and VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed: HLB, HID, HHB, HOH, and HLB–LP. There are three bars for each VES representing the Bottom, Middle, and Top measurement heights. Standard error bars are atop each bar. The following are the approximate ranges of background luminance for the different measurement heights. Bottom: 0.11 (HLB–LP) to 0.21 (HOH). Middle: 0.07 (HLB–LP) to 0.14 (HOH). Top: 0.03 (HLB–LP and HHB) to 0.06 (HID). In general, the measurements at the bottom measurement height appear to produce slightly larger standard errors. Back to Figure 40.

Figure 41. Bar graph. Influence of station on background luminance for the tire tread by VES. The graph is titled “Background Luminance of Tire Tread by Station and VES.” The Y-axis is labeled “Background Luminance (candela per square meter).” The X-axis is labeled “VES,” and the following VESs are listed: HLB, HID, HHB, HOH, and HLB–LP. There are five bars for each VES; each bar represents a specific station and is labeled accordingly as station 1, station 2, station 4, station 5, or station 6. Standard error bars are atop each bar. The following are the approximate ranges of background luminance for the different stations. Station 1: 0.04 (HID) to 0.15 (HLB). Station 2: 0.055 (HLB–LP) to 0.1 (HOH and HHB). Station 4: 0.08 (HLB–LP) to 0.2 (HOH). Station 5: 0.055 (HLB–LP and HHB) to 0.12 (HID). Station 6: 0.075 (HLB–LP) to 0.15 (HLB and HOH). In general, station five appeared to produce smaller standard errors of about plus or minus 0.01. HOH paired with station four produced a noticeably larger standard error of about plus or minus 0.1. Back to Figure 41.

Figure 42. Bar graph. Reflectance of all objects both dry and wet. The graph is titled “Reflectance of Objects by Wet and Dry Conditions and Object Type.” The Y-axis is labeled “Reflectance (percent).” The X-axis is labeled “Object,” and the following objects are listed: Black-Clothed, White-Clothed, Child’s Bicycle, and Tire Tread. There are two bars for each object; one bar represents the dry condition, and one bar represents the wet condition. Standard error bars are atop each bar. There is not a noticeable difference in the reflectance of the child’s bicycle between the wet and dry conditions. The black-clothed pedestrian had a reflectance of about three percent and four percent for the dry and wet conditions respectively. The white-clothed pedestrian had a reflectance of about 50 percent and 21 percent for the dry and wet conditions respectively. The tire tread had about 4 percent and 6 percent reflectance for the dry and wet conditions respectively. The black-clothed pedestrian and the tire tread produced smaller standard errors than the white-clothed pedestrian and the child’s bicycle. Back to Figure 42.

Figure 43. Bar graph. Specular reflection of all bicycle objects for both black-clothed and white-clothed cyclist. The graph is titled “Specular Reflection of the Bicycle Used by the Cyclist.” The Y-axis is labeled “Specular Reflection (percent).” The X-axis is labeled “Bicycle Color,” and there are two bars; one bar represents the dark bicycle, and one bar represents the light bicycle. Standard error bars are atop each bar. The dark bicycle has a specular reflectance of about 24 percent with a standard error of about plus or minus 7 percent. The light bicycle has a specular reflectance of about 6 percent with a standard error of about plus or minus 1 percent. Back to Figure 43.

Figure 44. Bar graph. Fluorescence for the black-clothed and white-clothed pedestrians by roadway position. The graph is titled “Pedestrian Fluorescence for Clothing Type by Pedestrian Type.” The Y-axis is labeled “Fluorescence (percent).” The X-axis is labeled “Pedestrian Type,” and the following pedestrian types are listed across the X-axis: Cyclist, Perpendicular, and Parallel. There are two bars for each pedestrian type; one bar represents black-clothed and one bar represents white-clothed. Standard error bars are atop each bar. The fluorescence of black-clothed pedestrians ranged from about 90 (perpendicular) to 110 (cyclist). The fluorescence of white-clothed pedestrians ranged from about 125 (parallel) to 190 (cyclist). Both the black-clothed perpendicular pedestrian type and the parallel pedestrian type produced noticeably smaller standard errors than the cyclist. Back to Figure 44.

Figure 45. Bar graph. Fluorescence for the black-clothed and white-clothed objects by VES type. The graph is titled “Pedestrian Fluorescence for Pedestrian Clothing by VES.” The Y-axis is labeled “Fluorescence (percent).” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: none, hybrid, three UV–A, and five UV–A. There are two bars for each VES; one bar represents black-clothed, and one bar represents white-clothed. Standard error bars are atop each bar. The fluorescence of black-clothed pedestrians ranged from about 90 (hybrid) to 110 (three UV–A). The fluorescence of white-clothed pedestrians ranged from about 100 (none) to 230 (five UV–A). The standard errors are comparable across white-clothed and black-clothed pedestrians within each VES, with the exception of five UV–A. The standard error for five UV–A is about plus or minus 25 (white-clothed pedestrian) and plus or minus 1 (black-clothed pedestrian). Back to Figure 45.

Figure 46. Bar graph. Fluorescence for the white-clothed objects by VES type and position on the roadway. The graph is titled “Fluorescence of White-Clothed Pedestrians for Pedestrian Type by VES.” The Y-axis is labeled “Fluorescence (percent).” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: none, hybrid, three UV–A, and five UV–A. There are three bars for each VES that represent the cyclist, the perpendicular pedestrian, and the parallel pedestrian. Standard error bars are atop each bar. The fluorescence for the three pedestrian types with no UV–A appear similar at about 100. The fluorescence with the hybrid UV–A ranges from about 99 (perpendicular pedestrian) to 125 (parallel pedestrian). The fluorescence with the three UV–A, ranges from about 125 (parallel pedestrian) to 275 (cyclist). The fluorescence with five UV–A ranges from about 156 (parallel pedestrian) to 275 (cyclist). Standard errors range from being unnoticeable with no UV–A to being about plus or minus 50 for the cyclist and three UV–A combination. Back to Figure 46.

Figure 47. Bar graph. Fluorescence of the child’s bicycle by VES type. The graph is titled “Fluorescence of Child’s Bicycle by VES.” The Y-axis is labeled “Fluorescence (percent).” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: None, Hybrid, Three UV–A, and Five UV–A. There is one bar for each VES. Standard error bars are atop each bar. The graph shows a steady increase in fluorescence as the level of UV–A is increased. The fluorescence ranges from about 100 with no UV–A to 280 with five UV–A. There is no noticeable standard error for the no UV–A condition. The standard errors for the different UV–A conditions are generally comparable. Back to Figure 47.

Figure 48. Bar graph. Luminance difference by VES for black-clothed pedestrians by object position. The graph is titled “Luminance Difference of Black-Clothed Objects by Pedestrian Type and VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES; one bar represents cyclist, one bar represents perpendicular pedestrian, and one bar represents parallel pedestrian. Standard error bars are on each bar. The cyclist’s contrast was negative across all VESs, ranging from negative 0.005 (five UV–A plus HLB and HLB–LP) to negative 0.0525 (HOH). The exceptions to this were three UV–A plus HLB (0.025) and HHB (0.025). The perpendicular pedestrian’s contrast ranged from negative 0.045 (HOH) to 0.055 (five UV–A plus HLB). The parallel pedestrian’s contrast ranged from negative 0.12 (HOH) to 0.05 (HID and three UV–A plus HID). The standard errors of most contrast means were as large as or larger than the means. The exceptions were perpendicular and parallel pedestrians with HID, three UV–A plus HID, and five UV–A plus HID. Back to Figure 48.

Figure 49. Bar graph. Luminance difference by VES for black-clothed pedestrians by measurement height. The graph is titled “Luminance Difference of Black-Clothed Cyclist by Measurement Height and VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following measurement heights: chest, waist, knee, and ankle. Standard error bars are on each bar. Chest height measurements showed about 0.04 level of contrast for all the HLB configurations. Chest height measurements were about negative 0.005 level of contrast for the HID configurations. Hybrid UV–A plus HID was an exception to this at about 0.001. Luminance difference for HHB at chest height was about 0.08. Luminance difference for HOH was about negative 0.01. Luminance difference for HLB–LP at chest height was about 0.025. Standard errors for chest height were generally comparable. Luminance differences for the waist height measurements ranged between about 0.04 and 0.055 for the HLB configurations. Luminance difference levels for waist height measurements with the HID configurations are so close to zero that they were difficult to determine. It appears contrast levels for hybrid plus HID and five UV–A plus HID are approximately 0.001. HHB at waist height had a contrast level of about 0.070. HLB–LP was about 0.025. Standard errors for waist height were generally comparable with HHB producing the largest standard error. Luminance difference for knee height measurements had negative contrast for HLB and hybrid plus HLB (about 0.02), and switched to positive contrast (about 0.01) when three and five UV–A were added to the HLB. Luminance differences for the HID configurations were so close to zero, that they were difficult to determine by viewing the graph. Luminance difference for knee paired with HOH was approximately negative 0.04, and paired with HLB–LP was about 0.01. Luminance difference for ankle height measurements all had a negative contrast except for three UV–A plus HID (.09). The negative contrasts ranged from about negative 0.16 (HOH with standard error of about plus or minus 0.1) to negative 0.06 (HHB). Back to Figure 49.

Figure 50. Bar graph. Luminance difference by VES for black-clothed pedestrians by measurement distance. The graph is titled “Luminance Difference of Black-Clothed Pedestrians by Distance and VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following measurement distances: 200 feet, 300 feet, 500 feet, and 800 feet. Standard error bars are present for each bar. The standard errors for the following combinations were larger than the mean contrast: HLB and 200 feet, HHB and 200 feet, HLB–LP and 200 feet. The only positive contrasts are for HID at 200 feet (about 0.0025) and HHB at 200 feet (about 0.0001). The overall trend of the graph shows that increasing the measurement distance generally produces a larger negative contrast. The following are the approximate contrast ranges for each VES. HLB: negative 0.01 (200 feet) to negative 0.14 (500 feet). HID: 0.025 (200 feet) to negative 0.02 (500 feet and 800 feet). HHB: 0.001 (200 feet) to negative 0.12 (800 feet). HOH: negative 0.025 (300 feet) to negative 0.07 (200 feet). HLB–LP: negative 0.0001 (200 feet) to negative 0.025 (800 feet). HID and HLB–LP produced noticeably smaller standard errors than the other VESs. Back to Figure 50.

Figure 51. Bar graph. Luminance difference by VES for white-clothed pedestrians by object position. The graph is titled “Luminance Difference of White-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following pedestrian types: cyclist, perpendicular, and parallel. The general trend of the graph shows that as UV level increases, the contrast also increases. The following are the contrast ranges for the pedestrian types. Cyclist: 0.4 (HID) to 3.25 (five UV–A plus HLB). Perpendicular: 0.5 (HOH) to 2.4 (five UV–A plus HLB). Parallel: 0.8 (HID) to 3.4 (five UV–A plus HLB). Standard errors were generally comparable. Back to Figure 51.

Figure 52. Bar graph. Luminance difference by VES for white-clothed pedestrians by measurement distance. The graph is titled “Luminance Difference of White-Clothed Pedestrians by Distance and VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following distances: 200 feet, 300 feet, 500 feet, and 800 feet. The general trend of the graph shows that as UV level increases, the contrast also increases, especially at 200 feet. The trend is less noticeable and has some exceptions at 300 and 500 feet. The trend does not exist at 800 feet. The following are the contrast ranges for the respective distances. At 200 feet: 1.1 to 3 with HLB configurations, 0.7 to 2 with HID configurations, 2 with HHB, and about 0.7 with HOH and HLB–LP. At 300 feet: 0.5 to 0.75 with HLB configurations, 0.3 to 0.65 with HID configurations, 0.65 with HHB, and about 0.25 with HOH and HLB–LP. At 500 feet: 0.05 to 0.15 with HLB configurations, 0.15 to 0.2 with HID configurations, 0.15 with HHB, 0 with HOH, and 0.05 with HLB–LP. At 800 feet: negative 0.05 to 0.03 with HLB configurations, 0.05 to 0.15 with HID configurations, negative 0.05 with HHB and HOH, and 0 with HLB–LP. Standard errors were generally comparable. Back to Figure 52.

Figure 53. Bar graph. Luminance difference by VES for the child’s bicycle. The graph is titled “Luminance Difference of Child’s Bicycle by VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. The general trend of the graph shows that as UV level increases, the contrast also increases. Luminance difference ranges from 0.4 to 1.35 with HLB configurations, 0.4 to 1.85 with HID configurations, 0.4 with HHB, 0.6 with HOH, and 0.25 with HLB–LP. Standard errors were generally comparable. Back to Figure 53.

Figure 54. Bar graph. Luminance difference by VES for the tire tread. The graph is titled “Luminance Difference of Tire Tread by VES.” The Y-axis is labeled “Luminance Difference.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, HID, HHB, HOH, and HLB–LP. The tire tread’s contrast values are: negative 0.035 with HLB, negative 0.008 with HID, 0.029 with HHB, 0.009 with HOH, and 0.09 with HLB–LP. The standard errors are larger than the means for HID and HOH. The standard error is about equal to the mean for HHB and HLB–LP. Only HLB’s standard error is smaller than its mean.
Back to Figure 54.

Figure 55. Bar graph. Visibility level by age and VES for the pedestrian objects. The graph is titled “Mean Visibility Level for Pedestrian Types by Age Group and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following age groups: young, middle, and older. The general trend of the graph shows that as UV level increases, the contrast also increases. For HLB configurations, visibility level ranged from 210 to 550 with young participants, 130 to 330 with middle-aged participants, and 75 to 180 with older participants. For HID configurations, visibility level ranged from 175 to 375 with young participants, 105 to 240 with middle-aged participants, and 60 to 120 with older participants. Visibility level for HHB, HOH, and HLB–LP followed the same trend of decreasing by one-half to one-third as age increased as with HLB and HID configurations. Visibility level with HHB decreased from 375 with young participants to 125 with older participants. Visibility level with HOH decreased from 130 with young participants to 45 with older participants. Visibility level with HLB–LP decreased from 210 with young participants to 75 with older participants. Standard errors are roughly proportional across all VESs. Back to Figure 55.

Figure 56. Bar graph. Visibility level by VES for the black-clothed pedestrian objects by position. The graph is titled “Visibility Level of Black-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. Visibility level of the cyclist is generally the least, ranging from 3 with HLB–LP to just greater than 10 with HHB. Visibility level of the perpendicular pedestrian is generally the next greatest (though it is barely greater than that of the parallel pedestrian with HLB), ranging from 8 with HLB–LP to 28 with HID. Visibility level of the parallel pedestrian is generally the greatest (with the exception noted above), ranging from 10 with HOH to 40 with HID. Standard errors are roughly proportional across all VESs, with the cyclist and HLB–LP having the smallest standard error and the parallel pedestrian with HID having the greatest. Back to Figure 56.

Figure 57. Bar graph. Visibility level by VES for the black-clothed pedestrian objects by distance. The graph is titled “Visibility Level of Black-Clothed Pedestrian Types by Distance and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following distances: 200 feet, 300 feet, 500 feet, and 800 feet. Visibility level at 300 feet with HOH and at 200 feet with HLB–LP are outstanding, roughly 2 to 2.5 times greater than the greatest visibility level of all the other distance and VES combinations. Visibility level at 200 feet ranges from 4 with HOH to 24 with HLB–LP. Visibility level at 300 feet ranges from 2 with HHB to 22 with HOH. Visibility level at 500 feet ranges from 4.5 with HID to 9 with HHB. Visibility level at 800 feet ranges from 2.5 with HLB–LP to 9.5 with HID. Standard errors are roughly proportional across all VESs, with 800 feet with HLB–LP having the smallest standard error and 300 feet with HOH having the greatest. Back to Figure 57.

Figure 58. Bar graph. Visibility level by VES for the white-clothed pedestrian objects by position. The graph is titled “Visibility Level of White-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. The general trend of the graph shows that as UV level increases, the visibility level also increases. The exception to this trend is the parallel pedestrian with HID configurations; visibility level with hybrid UV–A plus HID is slightly greater than with three UV–A plus HID and five UV–A plus HID. For HLB configurations, visibility level ranged from 450 to 1,250 for the cyclist, 400 to 800 for the perpendicular pedestrian, and 350 to 1,140 for the parallel pedestrian. For HID configurations, visibility level ranged from 240 to 1,050 for the cyclist, 380 to 650 for the perpendicular pedestrian, and 320 to 480 for the parallel pedestrian. For the HHB, HOH, and HLB–LP, visibility level ranged from 275 (HOH) to 790 (HHB) for the cyclist, 210 (HOH) to 700 (HHB), and 300 (HOH) to 670 (HHB). Standard errors are roughly proportional across VESs, with the perpendicular pedestrian and HLB–LP having the smallest standard error and the parallel pedestrian and five UV–A plus HLB having the greatest. Back to Figure 58.

Figure 59. Bar graph. Visibility level for the white-clothed pedestrians by distance and VES. The graph is titled “Visibility Level of White-Clothed Pedestrians by Distance and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following distances: 200 feet, 300 feet, 500 feet, and 800 feet. The general trend of the graph shows that as UV level increases, the visibility level also increases. The exceptions are at 300 feet with hybrid UV–A plus HLB and three UV–A plus HLB, where the visibility levels are roughly equal, at 300 feet with hybrid UV–A HLB and three UV–A plus HLB, where the latter is slightly smaller, at 500 feet with three UV–A plus HID, where the visibility level is slightly lower than with hybrid UV–A plus HLB, and at 800 feet with the HID configurations, where the trend reversed. In addition, visibility level decreases with distance for all VESs. For HLB configurations, visibility level ranged from 420 to 1,160 at 200 feet, 340 to 425 at 300 feet, 80 to 315 at 500 feet, and 20 to 30 at 800 feet. For HID configurations, visibility level ranged from 320 to 720 at 200 feet, 290 to 580 at 300 feet, 105 to 185 at 500 feet, and 45 to 65 at 800 feet. For the HHB, HOH, and HLB–LP, visibility level ranged from 270 (HOH) to 775 (HHB) at 200 feet, 190 (HOH) to 420 (HHB), 45 (HOH) to 105 (HHB) at 500 feet, and 10 (HOH and HLB–LP) to 25 (HHB). Standard errors are roughly proportional across VESs, with HLB–LP and HOH at 800 feet having the smallest standard error and five UV–A plus HID at 200 feet having the greatest. Back to Figure 59.

Figure 60. Bar graph. Visibility level for the child’s bicycle by age and VES. The graph is titled “Visibility Level of the Child’s Bicycle by Age and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following age groups: young participants, middle-aged participants, and older participants. The general trend of the graph shows that as UV level increases, the visibility level also increases. In addition, visibility level decreases with age for all VESs. For HLB configurations, visibility level ranged from 90 to 295 with young participants, 55 to 185 with middle-aged participants, and 25 to 100 with older participants. For HID configurations, visibility level ranged from 100 to 475 with young participants, 70 to 395 with middle-aged participants, and 35 to 165 with older participants. For the HHB, HOH, and HLB–LP, visibility level ranged from 85 (HLB–LP) to 125 (HOH) with young participants, 50 (HLB–LP) to 80 (HOH) with middle-aged participants, and 30 (HLB–LP) to 45 (HOH) with older participants. Standard errors are roughly proportional across VESs, with HLB–LP and older participants having the smallest standard error and five UV–A plus HID and young participants having the greatest. The HID configurations have, proportionally, the greatest standard errors. Back to Figure 60.

Figure 61. Bar graph. Visibility level for the tire tread by age and VES. The graph is titled “Visibility Level of Tire Tread by Age and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, HID, HHB, HOH, and HLB–LP. There are three types of bars for each VES that represent the following age groups: young participants, middle-aged participants, and older participants. In general, visibility level decreases with age. Visibility level increases going from HLB to HID to HHB, then decreases going from HHB to HOH to HLB–LP. Visibility level ranged from 3.5 (HLB) to 9.9 (HHB) with the young participants, 2.2 (HLB) to 6.2 (HHB) with the middle-aged participants, and 1.2 (HLB–LP) to 3.4 (HHB) with the older participants. Standard errors are as large or nearly as large as the measures for all VESs and ages except for HLB and, to a lesser extent, HOH. Back to Figure 61.

Figure 62. Equation. Weber ratio contrast equation. Contrast equals the maximum luminance minus the minimum luminance, that difference divided by the minimum luminance. Back to Figure 62.

Figure 63. Bar graph. Threshold Weber ratio for black-clothed pedestrian objects. The graph is titled “Weber Ratio of the Black-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Weber Ratio.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. Weber ratio ranged from 0.37 (hybrid UV–A plus HID) to 7.8 (HOH) for the cyclist, 0.39 (HID) to 0.62 (hybrid UV–A plus HLB) for the perpendicular pedestrian, and 0.44 (HLB–LP) to 0.66 (HHB) for the parallel pedestrian. Standard errors are comparable. Back to Figure 63.

Figure 64. Bar graph. Threshold Weber ratio for white-clothed pedestrian objects. The graph is titled “Weber Ratio of the White-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Weber Ratio.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, parallel pedestrian, and static pedestrian. Weber ratio of the cyclist and perpendicular pedestrian with HID configurations tend to be higher than the ratios of the other object and VES combinations. Weber ratio ranged from 0.58 (HLB–LP) to 0.89 (hybrid UV–A plus HID) for the cyclist, 0.55 (five UV–A plus HLB) to 0.86 (HID) for the perpendicular pedestrian, 0.57 (HID) to 0.7 (HLB) for the parallel pedestrian, and 0.54 (HOH) to 0.71 (HLB) for the static pedestrian. Standard errors are comparable. Back to Figure 64.

Figure 65. Bar graph. Threshold visibility level for black-clothed pedestrian objects. The graph is titled “Visibility Level at Threshold for Black-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. In general, visibility levels of the perpendicular and parallel pedestrians with HID, three UV–A plus HID, and five UV–A plus HID, as well as the parallel pedestrian with HHB, appear to be greater than the visibility levels of the other object and VES combinations. Also, visibility level of the cyclist is the smallest-with the exception of HHB, where it is slightly greater than the perpendicular pedestrian’s-followed by the perpendicular pedestrian’s visibility level, and the visibility level of the parallel pedestrian is greatest overall. Visibility level ranges from 0.5 (hybrid UV–A plus HID) to 3 (HHB) for the cyclist, 1.5 (hybrid UV–A plus HID) to 5 (five UV–A plus HLB) for the perpendicular pedestrian, and 1.8 (hybrid UV–A plus HID) to 8.2 (three UV–A plus HID) for the parallel pedestrian. Standard errors are comparable for most VESs, from nearly 0 to plus or minus 0.5. Standard errors for the perpendicular and parallel pedestrians with HID, three UV–A plus HID, and five UV–A plus HID are exceptionally large, ranging from plus or minus 1.1 to plus or minus 1.8. Back to Figure 65.

Figure 66. Bar graph. Threshold visibility level for white-clothed pedestrian objects. The graph is titled “Visibility Level at Threshold for White-Clothed Objects by Pedestrian Type and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, parallel pedestrian, and static pedestrian. Visibility levels range from 7 (HOH) to 46 (five UV–A plus HID) for the cyclist, 2 (HOH) to 30 (five UV–A plus HID) for the perpendicular pedestrian, 5 (HOH) to 26 (three UV–A plus HLB) for the parallel pedestrian, and 7 (HOH) to 34 (HID). Standard errors vary widely, from plus or minus 2 to plus or minus 42. The largest standard errors were associated with the static pedestrian with hybrid UV–A plus HLB, HID, and five UV–A plus HID, and HHB; the parallel pedestrian with three UV–A plus HLB; the cyclist with HID configurations and HLB–LP; the perpendicular pedestrian with five UV–A plus HID and HLB–LP; the parallel pedestrian with three UV–A plus HLB; and the static pedestrian with hybrid UV–A plus HLB, HID, five UV–A plus HID, and HHB. Back to Figure 66.

Figure 67. Bar graph. Threshold dosage factor for black-clothed pedestrian objects. The graph is titled “Dosage for Black-Clothed Objects by Pedestrian Type and VES.” The Y-axis is labeled “Dosage.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. The graph shows a general trend of increasing dosage from cyclist to perpendicular pedestrian to parallel pedestrian; the exceptions are hybrid UV–A plus HLB, where dosage is greatest for the perpendicular pedestrian, and HHB, where the trend is reversed. Dosage ranges from 0.0000005 with HOH to 0.0000018 with three UV–A plus HID for the cyclist, 0.0000018 with five UV–A plus HLB and hybrid UV–A plus HID to 0.0000069 with five UV–A plus HID for the perpendicular pedestrian, and 0.0000028 with HLB to 0.0000123 with three UV–A plus HID for the parallel pedestrian. Standard errors vary widely, from plus or minus 0.0000001 to plus or minus 0.0000034. The largest standard errors are associated with the perpendicular pedestrian with hybrid UV–A plus HLB, HID, three UV–A plus HID, five UV–A plus HID, and HHB and the perpendicular pedestrian with HID, three UV–A plus HID, and five UV–A plus HID. Back to Figure 67.

Figure 68. Bar graph. Threshold dosage factor for white-clothed pedestrian objects. The graph is titled “Dosage for White-Clothed Objects by Pedestrian Type and VES.” The Y-axis is labeled “Dosage.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are four bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, parallel pedestrian, and static pedestrian. Dosage ranges from 0.0000027 with HHB to 0.0000096 with HID for the cyclist, 0.0000008 with HOH to 0.000007 with five UV–A plus HID for the perpendicular pedestrian, 0.0000018 with HOH to 0.0000111 with three UV–A plus HLB for the parallel pedestrian, and 0.0000022 with HOH to 0.000013 with HID for the static pedestrian. Standard errors vary widely, from plus or minus 0.00000012 to plus or minus 0.0000073. Exceptionally large standard errors are associated with the static pedestrian with hybrid UV–A plus HLB, HID, five UV–A plus HID, and HHB; the parallel pedestrian with three UV–A plus HLB; the cyclist with HID, hybrid UV–A plus HID, and five UV–A plus HID; and the perpendicular pedestrian with HID, five UV–A plus HID, and HLB–LP. Back to Figure 68.

Figure 69. Equation. Transmittance of illuminance based on the ratio of the clear measurements. Tau subscript illuminance equals the quotient of uppercase E subscript weather divided by uppercase E subscript clear. Back to Figure 69.

Figure 70. Equation. Transmittance of luminance based on the ratio of the clear measurements. Tau subscript luminance equals the quotient of uppercase L subscript weather divided by uppercase L subscript clear. Back to Figure 70.

Figure 71. Bar graph. Transmittance of the atmosphere for the illuminance, object luminance, and background luminance in the rain. The graph is titled “Mean Transmittance Through Rain.” The Y-axis is labeled “Transmittance (percent).” The X-axis is labeled “Measurement Source” and is broken into three categories: illuminance, object luminance, and background luminance. Illuminance has 23 percent transmittance, object luminance has 13 percent transmittance, and background luminance has 29 percent transmittance. Standard errors are all comparable at about plus or minus 1.5 percent. Back to Figure 71.

Figure 72. Line graph. Illuminance for both clear and snow conditions. The graph is titled “Illuminance through Snow and Clear Conditions.” The Y-axis is labeled “Illuminance (lux).” The X-axis is labeled “Distance from Vehicle (feet).” There are two lines which both start at 50 feet and end at 300 feet. One line represents the clear condition, and one line represents the snow condition. Illuminance for the clear condition at 50 feet is 8.5, while illuminance for the snow condition at the same distance is at 15.5. Their relative positions reverse at 100 feet to 11 for the snow condition and 14 for the clear condition. Illuminance for both conditions fall steeply to 1 for the snow condition and 6 for the clear condition at just under 200 feet and fall gradually to just over 0 for the snow condition and just under 4 for the clear condition at 300 feet.
Back to Figure 72.

Figure 73. Line graph. Transmittance of the atmosphere for the illuminance through snow. The graph is titled “Illuminance Transmissivity.” The Y-axis is labeled “Transmissivity (percent).” The X-axis is labeled “Distance from Vehicle (feet).” There is a single line representing series 1. The line begins at an illuminance of 77 percent at 100 feet, falls sharply to an illuminance of 26 percent at 150 feet, then falls gradually to an illuminance of 3 percent at 300 feet. Back to Figure 73.

Figure 74. Diagram. Possible reaction of light after collision with a water particle in a fog bank. The illustration shows a light bulb emitting light in all directions. An arrow, representing a ray of light, extends from the right side of the bulb and ends when it hits a round water particle. The pattern of light dispersal from the water particle has two small, rounded portions to the particle’s left connected to two sharp extensions up and down, which are in turn connected to one long, round portion to the right of the particle. Back to Figure 74.

Figure 75. Equation. Intensity of light based on the scattering coefficient and incident illuminance. Uppercase I as a function of theta equals beta as a function of theta times uppercase E subscript incident.
Back to Figure 75.

Figure 76. Diagram. Depiction of the incident beam broken into small lamina. This diagram depicts a rectangular block, separated into sections of width DX via vertical partitions, onto which an arrow labeled E subscript naught is projected. The sections (lamina) become progressively darker as they are further from the arrow. Back to Figure 76.

Figure 77. Equation. Differential change in illuminance for each portion of a light beam. Lowercase d uppercase E divided by uppercase E subscript naught equals negative beta times lowercase dx.
Back to Figure 77.

Figure 78. Equation. Total attenuation according to Bouguer’s law. Uppercase E subscript lowercase x equals uppercase E subscript naught times lowercase e to the power negative beta times lowercase x.
Back to Figure 78.

Figure 79. Equation. Reduction caused by the fog attenuation. Uppercase C subscript lowercase x equals uppercase C subscript naught times lowercase e to the power of negative beta times lowercase x.
Back to Figure 79.

Figure 80. Scatter plot. Measured backscatter versus the beta(theta) function. The graph is titled “Backscatter versus Beta.” The Y-axis is labeled “Beta.” The X-axis is labeled “Backscatter.” There are four types of points that represent the following VESs: HLB SUV 1, HLB SUV 2, HID, and HLB–LP. The values for HLB SUV 1 and HLB SUV 2 each form a loose diagonal line rising left-to-right from about 0.06 backscatter and 0 beta to about 0.4 backscatter and 0.029 beta. The majority of points for HLB SUV 2 fall below 0.01 beta. The values for HID and HLB–LP form a tighter left-to-right diagonal line grouping from about 0.175 backscatter and 0 beta to 0.42 backscatter and 0.022 beta. The points are distributed about equally throughout the group; there is one outlier for HID at 0.52 backscatter and 0.006 beta. Back to Figure 80.

Figure 81. Scatter plot. Measured backscatter versus the extinction factor. The graph is titled “Backscatter versus Extinction.” The Y-axis is labeled “Extinction.” The X-axis is labeled “Backscatter.” There are four types of points that represent the following VESs: HLB SUV 1, HLB SUV 2, HID, and HLB–LP. The values for HLB SUV 1 and HLB SUV 2 form two clusters. The first cluster contains the majority of these VESs’ points and forms a loose group between about 0.03 backscatter to 0.4 backscatter and 0 extinction to 0.2 extinction with more points falling below 0.1 extinction than above it. The second cluster is a loose column extending from 0.06 backscatter to 0.15 backscatter and from 0.38 extinction to 1 extinction. Values for HID and HLB–LP form a loose reverse J shape, falling left-to-right, from about 0.2 backscatter and 1 extinction to 0.4 backscatter and 0 extinction. HID has one outlier at 0.52 backscatter and 0.55 beta. Back to Figure 81.

Figure 82. Equation. Beta(theta) function based on the adjusted backscatter. Beta equals 0.0324 times the difference of 1 minus lowercase e where lowercase e is to the following power: negative 3.92 times the difference of uppercase B lowercase sc minus lowercase a. Back to Figure 82.

Figure 83. Equation. Extinction factor based on the adjusted backscatter. Uppercase E lowercase x equals lowercase e to the power of negative 16.35 times the difference of uppercase B subscript lowercase sc minus lowercase a. Back to Figure 83.

Figure 84. Scatter plot. Backscatter versus beta by model. The graph is titled “Backscatter versus Beta.” The Y-axis is labeled “Beta.” The X-axis is labeled “Backscatter.” There are four types of points that represent the following VESs: HLB SUV 1, HLB SUV 2, HID, and HLB–LP. There are three lines on the graph that represent model SUV 1 and 2, model HID, and model HLB–LP. The line for model SUV 1 and 2 is a gentle curve up and to the right, starting at 0.06 backscatter and 0 beta and ending at 0.55 backscatter and 0.028 beta. The values for HLB SUV 1 and HLB SUV 2 generally follow this curve, but tend to be slightly above it. The model HLB–LP’s line is a gentle curve up and to the right, starting at 0.15 backscatter and 0 beta and ending at 0.55 backscatter and 0.0255 beta. The values for HLB–LP generally follow this curve, but tend to be slightly below it. The model HID’s line is a gentle curve up and to the right, starting at 0.21 backscatter and 0 beta and ending at 0.55 backscatter and 0.024 beta. The values for HID generally follow this curve, but tend to be slightly above it. HID has one outlier at 0.52 backscatter and 0.0052 beta. Back to Figure 84.

Figure 85. Scatter plot. Backscatter versus extinction with model. The graph is titled “Backscatter versus Extinction.” The Y-axis is labeled “Extinction.” The X-axis is labeled “Backscatter.” There are four types of points that represent the following VESs: HLB SUV 1, HLB SUV 2, HID, and HLB–LP. There are three lines on the graph that represent model SUV 1 and 2, model HID, and model HLB–LP. The line for model SUV 1 and 2 is a reverse J, falling left-to-right, starting at 0.7 backscatter and 1 extinction and ending at 0.55 backscatter and 0 extinction. The values for HLB SUV 1 and HLB SUV 2 very loosely follow this curve, though many points fall below and to the left of the sharpest portion of the curve. The line for the model HLB–LP is a reverse J, falling left-to-right, starting at 0.15 backscatter and 1extinction and ending at 0.55 backscatter and 0 extinction. The majority of values for HLB–LP follow this curve very closely, but several points fall to the right of it. The line for the model HID is a reverse J, falling left-to-right, starting at 0.23 backscatter and 1extinction and ending at 0.55 backscatter and 0 extinction. Most of the values for HID follow this curve very closely, but a few points fall below and to the left of the sharpest portion of the curve. HID has one outlier at 0.52 backscatter and 0.55 extinction. Back to Figure 85.

Figure 86. Bar graph. Threshold Weber ratio for white-clothed pedestrian objects in rain condition. The graph is titled “Weber Ratio for Rain and White-Clothed Pedestrian by Pedestrian Type and VES.” The Y-axis is labeled “Weber ratio.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, and HLB–LP. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. The trend of the graph shows that the cyclist had a slightly greater Weber ratio than the parallel and perpendicular pedestrians with HLB and HID configurations. Overall, the Weber ratios are all fairly similar, the exception being HOH, which was slightly lower overall than the other VESs. Weber ratios range from 0.77 with HOH to 0.97 with five UV–A plus HID for the cyclist, 0.82 with HOH to 0.92 with HLB–LP for the parallel pedestrian, and 0.8 with HOH to 0.92 with HLB–LP for the perpendicular pedestrian. Standard errors are small across all VESs, no more than plus or minus 0.08. Back to Figure 86.

Figure 87. Bar graph. Threshold visibility level for white-clothed pedestrian objects in rain condition. The graph is titled “Visibility Level in Rain for White-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Visibility Level.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, HLB–LP, and IR–TIS. There are three bars for each VES that represent the following object types: cyclist, perpendicular pedestrian, and parallel pedestrian. Visibility level ranges from 45 with HOH to 220 with five UV–A plus HID for the cyclist, 77 with HOH to 215 with five UV–A plus HLB for the parallel pedestrian, and 55 with HOH to 175 with five UV–A plus HID. Standard errors vary from plus or minus 8 with HOH for the perpendicular pedestrian to plus or minus 30 with five UV–A plus HID. Overall, the cyclist has the highest standard error. Back to Figure 87.

Figure 88. Bar graph. Threshold dosage for white-clothed pedestrian objects in rain condition. The graph is titled “Dosage for Rain and White-Clothed Pedestrians by Pedestrian Type and VES.” The Y-axis is labeled “Dosage.” The X-axis is labeled “VES,” and the following VESs are listed across the X-axis: HLB, hybrid UV–A plus HLB, three UV–A plus HLB, five UV–A plus HLB, HID, hybrid UV–A plus HID, three UV–A plus HID, five UV–A plus HID, HHB, HOH, HLB–LP, and IR–TIS. There are three bars for each VES that represent the following object types: cyclist, parallel pedestrian, and perpendicular pedestrian. Dosage ranges from 0.00004 with HOH to 0.00024 with HHB for the cyclist, 0.000051 with HID to 0.000165 with five UV–A plus HLB for the parallel pedestrian, and 0.00004 with hybrid UV–A plus HID to 0.00017 with HHB for the perpendicular pedestrian. Standard errors vary from plus or minus 0.000006 with HOH to plus or minus 0.000032 with five UV–A plus HLB. Back to Figure 88.

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United States Department of Transportation - Federal Highway Administration