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 : This study aimed to examine the effect of fog on the optical properties of taillights and the relationship between luminous intensity and the visibility distance of taillights on the road. METHODS : Changes in luminous intensity were measured using a light meter. Participants subjectively evaluated visibility distance. The artificial fog was reproduced using weather-generating facilities at the Center of Road Weather Proving Ground (CRPG). RESULTS : As expected, the average luminous intensity under intermediate fog conditions was reduced to 72% compared to normal weather conditions and 44% under heavy fog conditions in the case of the tail lamp-only lit condition. In the case of the tail lamp and brake lamp lit condition, the average luminous intensity was reduced to 76% under heavy fog conditions and 55% under intermediate fog conditions compared to normal dry conditions. In addition, the average visibility distance was reduced by 41% when fog conditions changed from intermediate to heavy in the case of the tail lamp-only lit condition and 39% in the case of the tail lamp and brake lamp lit conditions. Changes in visibility distance corresponding to the gradual change in luminous change were evaluated by participants, and the linearly regressed equations for the relationship between the intensity levels and the visibility distance were derived and examined for their meaning in terms of road traffic safety concerning stopping sight distance. CONCLUSIONS : Luminous intensities were suggested, given the design speeds, to satisfy the minimum stopping distances. In addition, the required speed reduction allowances were suggested given the design speeds if the luminous intensity remains unchanged.

PURPOSES : In this study, the relationship between the types of road pavement markings and the visibility distance under adverse weather conditions was evaluated. METHODS : Rainy and foggy conditions at the weather proving ground were replicated in this study. The researchers recorded the visibility distance corresponding to each experiment scenario comprising the weather conditions and pavement marking types. RESULTS : Visibility distances under adverse weather conditions decreased more than those of normal weather conditions. Under rainy conditions, the average visibility distance across all pavement markings decreased by 33%. However, the average visibility distance across all pavement markings foggy conditions decreased by 46.8%. Based on the test results of the visibility distance, the speed reduction rates corresponding to the adverse and normal weather conditions, i.e., 24% and 36% speed reduction under rainy and foggy conditions, respectively, were established. CONCLUSIONS : This study validated the reduction in the visibility distance affected by weather conditions by applying actual road scale weather proving ground. In addition, speed reduction was recommended for safe driving under adverse weather conditions.

PURPOSES : The purpose of this study is to analyze the impact of the level of the light-environment and the driver's visual ability on the change in the driver's perception of a forward curved section at night. The study also aims to identify factors that should be considered to ensure safety while entering curved sections of a road at night. METHODS : Data collected from a virtual driving experiment, conducted by the Korean Institute of Construction Technology (2017), were used. Logistic regression was applied to analyze the effects of changes in the light-environment factors (road surface luminance and glare) and the driver’s visual ability on a driver's perception of the road. Additionally, analysis of the moderated effect of visual ability on light-environment factors indicated that the difference in drivers’ visual abilities impact the influence of light-environment factors on their perception. A driver's ability to perceive, as a response variable, was categorized into 'failure' and 'success' by comparing the perceived distance and minimum reaction sight distance. Covariates were also defined. Road surface luminance levels were categorized into 'unlit road surface luminance' (luminance ≤ 0.1 nt) and 'lit road surface luminance' (luminance > 0.1 nt), based on 0.1 nt, which is the typical level observed on unlit roads. The glare level was categorized as 'with glare' and 'without glare' based on whether the glare was from a high-beam caused by an oncoming vehicle or not. The driver's visual ability level was categorized into 'low visual ability' (age ≥ 50) and 'high visual ability' (age ≤ 49), considering that after the age of 50, the drive’s visual ability sharply declines. RESULTS : The level of road surface luminance, glare, and driver's visual ability were analyzed to be significant factors that impact the driver's ability to perceive curved road sections at night. A driver's perception was found to reduce when the road surface luminance is very low, owing to the lack of road lighting ('unlit road luminance'), when glare is caused by oncoming vehicles ('with glare'), and if the driver's visual ability level is low owing to an older age ('low visual ability'). The driver's ability to perceive a curved section is most affected by the road surface luminance level. The effect is reduced in the order of glare occurrence and the driver's visual ability level. The visual ability was analyzed as a factor that impacts the intensity of the effect of change of the light-environment on the change of the driver's ability to perceive the road. The ability to perceive a curved section deteriorates significantly in 'low visual ability' drivers, aged 50 and above, compared to drivers with 'high visual ability,' under the age of 49, when the light-environment conditions are adverse with regard to the driver’s perception (road surface luminance: 'lit road surface luminance'→'unlit road surface luminance,' glare: 'without glare'→'with glare'). CONCLUSIONS : Supplementation, in terms of road lighting standards that can lead to improvements in the level of light-environment, should be considered first, rather than the implementation of restrictions on the right of movement, such as restricting the passage of low visual ability or aging drivers who are disadvantageous in terms of gaining good perception of the road at night. When establishing alternatives so that safety on roads at night is improved, it is necessary to consider improving drivers' perception by expanding road lighting installation. The road lighting criteria should be modified such that the glare caused by oncoming traffic, which is an influential factor in the linear change in perception, and the level of light-environment thereof are improved.

The relationship between width of line target and distance at the limit of discrimination was examined by means of the behavioral method, for filefish Stephanolepis cirrhifer from 11 to 15cm body length. Target distance was distance from beginning of partition board to target plate, and was varied from 50cm to 200cm. The target plate was made of white acrylic resin with a vertical black line in the center. The width of line target was varied from 0.2mm to 8.0mm. Fish were trained to respond to a line target and the width of line target reduced until the minimum width required to elicit a response was established. Rate of success was expressed as the percentage of target choices in 90 trials. The line acuity of filefish was found to be 0.58 at a target distance of 50cm. The rate of success decreased slowly as line target width decreased from 8.0mm to 1.5mm, and decreased suddenly for target widths less than about 1.5mm. The width of the line target D(mm) at the limit of discrimination was shown to be an exponential function of the target distance L(cm) as follows : D=exp(9.947×10-3.L+0.146)

본 논문에서는 국내 무역항 항로에 배치되는 등부표의 최적 배치에 대한 기준을 설정하기 위한 기초자료로서 항해자들을 대상으로 등부표의 시인거리와 배치에 대한 선호를 분석하였다. 무역항의 각 규모를 감안하여 항만별로 약 30~150부의 설문지를 배포하였고, 총 356부의 유효한 설문지가 분석에 사용되었다. 육안으로 청명한 날씨의 주간에 부표를 인지하는 거리는 2~4마일이 55.0%로 가장 많았다. 부표의 배치방식에서는 양측 부표방식의 선호가 62.1%로써 가장 높았다 또한 부표의 전후사이의 선호 간격은 평균 1.09마일이었다 쌍안경 없이 시인할 수 있는 부표의 기수는 2기가 40.6%로 가장 선호되었다.