PURPOSES : The purpose of this study was to analyze the visibility of lanes according to the changes in the plane and longitudinal line of roads considering the horizontal and vertical diffusion angles of vehicle headlights at night. First, the visibility length of the lane was determined according to the plane linearity of the road such that it could be applied to simulation and visualization data. Second, the night vision length of the lane was established according to the longitudinal line of the road such that it could be applied to the simulation and visualization data. METHODS : In this study, each variable is first examined to consider the horizontal and vertical diffusion angles of the vehicle headlights. Second, the equation for the visibility of the lane by vehicle headlights in planar linearity is obtained, and the visibility of the lane is determined. Third, an equation is obtained for the visibility of the lane by vehicle headlights in longitudinal linearity. RESULTS : The results of this study are as follows. First, the visibility length of the lane in the section where the plane linearity of the highway existed at night was studied. In this case, the visibility length of the right and left lanes based on the vehicle decreased according to the plane linearity of the highway. Second, the visibility length of the lane in the section where the longitudinal line of the highway existed at night was investigated. In this case, the visibility length of the lane decreased according to the change in the longitudinal line of the highway. CONCLUSIONS : Considering the horizontal and vertical diffusion angles, the visibility length of the lane was determined according to the changes in the plane and vertical line of the road. It can be applied to simulation and visualization data. In general, the visibility length considering the spread angle of the vehicle headlights was shorter than the visibility length of the lane by the headlights; roads must be designed in consideration with the above result.

PURPOSES : The current practice in car headlight visibility performance evaluation is based on the luminous intensity and illuminance of headlight. Such practice can be inappropriate from a visibility point of view where visibility indicates abilities to perceive an object ahead on the road. This study aimed at evaluating the appropriateness of current headlight evaluation methodMETHODS: This study measured the luminance of object and road surface at unlit roadways. The variables were measured by vehicle type and by headlight lamp type. Based on the measurements, the distance where drivers can perceive an object ahead was calculated and then compared against such distance obtained by conventional visibility performance evaluation.RESULTS: The evaluation method based on illuminance of headlight is not appropriate when viewed from the visibility concept that is based on object-perceivable distance. Further, the results indicated a shorter object-perceiving distance even when road surface luminance is higher, thereby suggesting that illuminance of headlight and luminance of road surface are not the representative indices of nighttime visibility.CONCLUSIONS : Considering that this study utilized limited vehicle types and that road surface (background) luminance can vary depending on the characteristics of the given road surface, it would likely go too far to argue that this study’s visibility performance evaluation results can get generalized to other conditions. Regardless, there is little doubt that the current performance evaluation criterion which is based on illuminance, is unreasonable. There should be future endeavors on the current subject which will need to explore study conditions further, under which more experiments should be conducted and effective methodologies developed for evaluating automotive headlight visibility performance. Needs are recognized particularly in the development of headlight visibility performance evaluation methodology which will take into account road surface (background) luminance and luminance contrast from various perspectives as the former indicates the driver’s perception of the front road alignment and the latter being indicative of object perception performance.

도로 조명은 설치 및 유지관리 비용의 부담으로 인해 설치장소가 극히 제한되고 있으며 이로 인해 국내 고속․일반국도의 88%가 무조명 구간으로 존치되고 있는 실정이다. 야간 무조명 도로 구간은 전방의 시거 제약으로 인해 매우 위험한 주행환경이다. 무조명 구간을 주행하는 운전자는 차량 전조등을 통해 전방의 상황을 확인하고 위험 상황에 대처할 수밖에 없다. 반면 자동차 전조등의 조사 길이에는 한계가 있으며, 더욱이 전조등 조정의 번거로움으로 인해 하향등 상태로 주행하는 것이 일반적임을 고려 시 무조명 구간 에서 국내 도로 설계 기준에서 제시하고 있는 정지거리의 확보는 거의 불가한 상황이다. 야간 도로를 주행 중인 운전자가 전방 장애물을 확인하기 위해서는 노면과 장애물의 밝기 차이, 즉 휘도 차이가 일정 수준 이상이어야 한다. 이에 본 연구는 정지거리 110m(설계속도 80kph)에서 표준 장애물 (15×15 cm2)의 확인을 위해 필요한 노면 및 장애물의 휘도 관계를 규명하기 위한 실내 축소 모형 실험을 수 행하였으며, 이 결과를 실제 무조명 도로 구간에서 측정된 차종 별, 전조등 상태별로 측정된 휘도 관계와 비교, 분석하여 차량 전 조등을 통한 시인성 확보 수준을 검토하였다. 실내 축소 모형 실 험은 야간 도로를 주행 중인 운전자의 시야 내 휘도 분포 변화를 표준적으로 묘사한 시환경 모사 시뮬레이터를 제작, 활용하여 수 행되었으며, 차량 전조등에 의한 휘도는 차량 전방 40m~180m 거리에 20m 간격으로 배치된 표준장애물과 그 주변의 노면 휘도 를 휘도 측정 장비(LMK5)를 이용하여 측정되었다(그림 1 참조). 본 실험을 통해 도출된 결과는 그림 2와 같다. X축은 노면 휘도 (road surface luminance), Y축은 장애물 휘도(object luminance) 이며, 음영으로 표시된 영역은 실내 축소모형에서 도출된 장애물 확인 불가능 영역(시인 불가 영역, invisible area), 이외의 영역은 각각 노면 휘도보다 더 밝은 장애물 휘도 조건 및 더 어두운 조건에 서의 장애물 확인 가능 영역(시인 가능 영역, visible area)이다. 표 시된 점은 차종별(승용, RV), 전조등 상태별(상향등, 하향등), 거리 별로 측정된 노면 휘도와 장애물 휘도의 관계이다. 분석결과 차량 전조등만으로 장애물 확인이 가능한 차량과 장애물 간 최대 거리는 하향등의 경우 RV 차량은 약 70m, 승용 차량은 40m, 상향등의 경 우 RV, 승용 차량 모두 약 100m이며, 따라서 무조명 구간에서 차량 전조등만으로 정지거리 110m(설계속도 80kph)의 확보는 불가한 것 으로 분석되었다. 따라서 무조명 구간에서 정지거리를 확보하기 위 해서는 차량 전조등의 한계를 보완하기 위한 조명 설치가 필요할 것 으로 판단된다.

A test was conducted using two high density discharge lamps, the H2D and the structurally new H4D. They were tested for luminous illumination and luminous temperature in the day and night time. The test was conducted without crippling the performance of the H2D by adding a magnetic actuator, enabling it to move left to right, and up and down. By making these modifications we constructed a sample of the H4D. We compared the H2D and the H4D sample's luminous illumination and luminous temperature by using a photometer and a digital thermometer in the day and night time. We discovered that the H2D and H4D performed similarly from the data we gathered. Now we know the H4D has potential use and extensive research needs to be made to gather more detailed data.