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Publication Number: FHWA-HRT-04-138
Date: December 2005

Enhanced Night Visibility Series, Volume VII: Phase II—Study 5: Evaluation of Discomfort Glare During Nighttime Driving in Clear Weather

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Figure 1. Equation. Schmidt-Clausen and Bindels equation. W equals the difference between 5.0 and the following product: 2.0 multiplied by the logarithm (base 10) of a quotient with numerator of E subscript lowercase I and denominator of the following: 0.003 multiplied by the sum of 1 plus the square root of the following quotient: L subscript lowercase A divided by 0.04, this product multiplied by theta subscript lowercase I to the 0.46 power. Back to Figure 1.

Figure 2. Photo. Headlamp setup on black SUV with hybrid UV-A and HID. The picture shows the front end of a black SUV. On a modular light rack mounted in front of the vehicle’s headlamps are two triangular HID headlamps. Set just a little farther in on the rack are two smaller, rectangular hybrid UV-A headlamps. Back to Figure 2.

Figure 3. Photo. Headlamp setup on white SUV with five UV-A and HLB. 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. Taking up almost all the space between them are three round, black UV-A headlamps. Two more UV-A lamps hang beneath the HLB lamps. Back to Figure 3.

Figure 4. Photo. Smart Road. The photo is an aerial view of a section of the Smart Road. The section of road is fairly straight with one gradual curve. The photo shows that there are no other structures in the immediate vicinity. Back to Figure 4.

Figure 5. Diagram. Experimental onroad setup. The diagram shows a vertical bird’s-eye view of a section of a two-lane road. At the top, a red glare vehicle is shown in the left lane with its headlamps on. The two vehicles are shown approaching each other from opposite directions. At the bottom, a vehicle marked “participant vehicle” is shown in the right lane with its lights on. Distances of the far and near discomfort rating sections between the two vehicles are marked with the respective discomfort rating instructions as follows, starting in front of the participant vehicle. Section 1: 1,300 feet-Begin thinking about your rating. 1,000 feet-What is your rating? Section 2: 450 feet-Begin thinking about your rating. 150 feet-What is your rating? Back to Figure 5.

Figure 6. Diagram. Location of luminance measurement points to determine adaptation level. The line drawing shows a horizontal bird’s-eye view of a section of two-lane road. A compact vehicle with its low beams on is in the right lane on the left side of the drawing. Measurement grid points are marked on the road by small circles with centered crosses. The grid points are arranged in seven columns spaced 5 meters apart down the length of the road, including 5 meters from the front of the vehicle to the first column of grid points, and four rows spaced 1.8 meters apart across the road’s width and 0.9 meters from the lane boundaries. Back to Figure 6.

Figure 7. Graph. Near discomfort rating versus VES for each age group. The Y-axis of this scatter plot shows average deBoer rating from bottom to top as follows: 1.0 (Unbearable), 2.0, 3.0 (Disturbing), 4.0, 5.0 (Just Acceptable), 6.0, 7.0 (Satisfactory), 8.0, and 9.0 (Just Noticeable). The X-axis shows VES names left to right as follows: three UV-A + HID, five UV-A + HID, HID, HLB-LP, hybrid UV-A + HID, HLB, hybrid UV-A + HLB, five UV-A + HLB, three UV-A + HLB, HOH, and HHB. Each age group, older, middle, and young, has its own style of data point. The scatter plot shows general agreement among all three age groups. Data points move gradually down the scale from about 6.0 on the left to about 3.0 near the middle, indicating increasing discomfort with VESs in this order: three UV-A + HID, five UV-A + HID, HID, HLB-LP, hybrid UV-A + HID, HLB, and hybrid UV-A + HLB. At this point, the data levels out at about 3.0, indicating similar discomfort with hybrid UV-A + HLB, five UV-A + HLB, three UV-A + HLB, HOH, and HHB. Three VESs show significant disagreement among the three age groups. For three UV-A + HID, the old and middle-aged groups reported less discomfort (between 6.0 and 7.0) than the young group (between 4.0 and 5.0). For HID, the middle-aged participants reported less discomfort (6.0) than the young group (just over 4.0). For the hybrid UV-A + HLB, the middle-aged group reported less discomfort (almost 4.0) than the young group (just over 2.0). Back to Figure 7.

Figure 8. Equation. Variation of Schmidt-Clausen and Bindels equation based on maximum illumination experienced. W equals the difference between 6.79 and the following product: 2.0 multiplied by the logarithm (base 10) of a quotient with the numerator E subscript max and denominator of the following: 0.003 multiplied by the sum of 1 plus the square root of the following quotient: L subscript A divided by 0.04, this product multiplied by theta subscript max to the 0.46 power. Back to Figure 8.

Figure 9. Equation. Variation of Schmidt-Clausen and Bindels equation based on last illumination experienced. W equals the difference between 6.61 and the following product: 2.08 multiplied by the logarithm (base 10) of a quotient with the numerator E subscript last and denominator of the following: 0.003 multiplied by the sum of 1 plus the square root of the following quotient: L subscript A divided by 0.04, this product multiplied by theta subscript last to the 0.46 power. Back to Figure 9.

Appendix C. Diagram. Contrast sensitivity test. The diagram shows the form the experimenters used to document the results for each participant’s contrast sensitivity exam. The diagram shows a graph with contrast sensitivity from 3 to 300 on the left Y-axis, contrast threshold from 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. There are two diagrams, one for recording the results of the right eye and one for the results of the left eye. Back to Diagram.

Figure 10. Photo. Aerial view of the Smart Road. The photograph shows a paved road with a large turnaround at one end extending down into a valley at the other end. Back to Figure 10.

Appendix G. Diagram. Hotspot location diagram for HLB, HID, and HOH headlamp configurations. The diagram depicts a set of crosshairs with a circle centered in the lower right corner. The caption above the diagram says “Hotspot Location: The circle represents the target hotspot location with respect to the target crosshairs. The center of the circle is the center of the hotspot.” Back to Diagram.

Appendix G. Diagram. Hotspot location diagram for UV-A headlamp configurations. 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.

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