Sag Vertical Curve Design Criteria for Headlight Sight Distance (2013) / Chapter Skim
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5 CHAPTER 3 REVIEW OF HEADLAMP DESIGN As SD is one of the limiting factors in the design of vertical curves it is the critical component which must be considered in the assessment of the sag curve design criteria. For sag vertical curves, SD is limited to that which is allowed by the vehicle's headlamps.
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6 Headlamps with light-emitting diode (LED) light sources were first installed in 2008 (Whitaker, 2007)
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7 Figure 4. Light allowed above horizontal by SAE standards.
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8 In 1993, Sivak, Flannagan, and Sato conducted a study which measured the light output of 150 headlamps from the United States, Europe, and Japan. By taking the median output for each group, they were able to create isocandela diagrams of the "typical" headlamp for each region for the time period.
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9 Figure 5. Isocandela diagrams of the median luminous intensities for U.S.
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10 conventional U.S. headlamps (Sivak, Flannagan, & Miyokawa, 2000)
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11 Figure 7. Test points (top)
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12 Figure 8. Isocandela diagrams of the median luminous intensities for sales-weighted sample representing the low-beam headlamps on current passenger vehicles in the U.S.
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13 In 2005, the Federal Highway Administration (FHWA) published the Enhanced Night Visibility (ENV)
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14 Table 2. Detection Distance by Type of Object and Potential Detection Inadequacy when compared to Stopping Distance at Various Speeds: HID Type of Object Det.
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15 In addition to the light source, headlamps must incorporate methods for distributing the light in the desired pattern. Early headlamps used lens optics.
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