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.

Rail wear in a curved track costs significant amount of maintenance efforts every year. The rail wear is affected by such parameters as train speed, curve radius, and insufficient cant. However, while the effect of train speed and curve radius to the rail wear is relatively well-known, the effect of the insufficient cant has not analytically researched sufficiently. In this paper, the effect of the insufficient cant on rail wear is studied using a multibody dynamics program, the Vi-Rail. The multibody analysis is performed using an EMU train model being operated in the urban railway. The hard track is utilized in the analysis. To identify the relationship between rail wear and insufficient cant. the wear analysis is conducted for various train speeds and curve radius based on the Archard model built in the Vi-Rail program. The analysis result reveals that, as the insufficient cant increases, the vertical and horizontal wear of the outer rail increases, but the wear of the inner rail does not show distinct trend.

PURPOSES : This study aims to evaluate the road safety of the super-elevation transition section of a left turn curve and suggest the minimum longitudinal grade of a super-elevation transition section to be used before and after a left curved section. METHODS: We evaluated the road condition by means of the safety-criterion-evaluation method involving side friction factors, and then solve the problem by introducing the minimum longitudinal grade criterion based on conditions described in the hydraulics literature. RESULTS : It was calculated that when a road satisfies hydroplaning conditions, the difference between side friction assumed and side friction demanded is less than - 0.04. In this case, the safety criterion for the condition is unsatisfied. Conversely, when a road is in a normal state under either wet or dry conditions, it was calculated that the difference between side friction assumed and side friction demanded is more than 0.01. Thus, the safety criterion for this condition is found to be satisfied. After adjusting the minimum longitudinal grade applied to a super-elevation transition section, the hydroplaning condition can be eliminated and the safety criterion can be met for all sections. CONCLUSIONS : It is suggested that a minimum longitudinal grade should be provided on super-elevation transition sections in order to prevent hydroplaning.

본 연구에서는 도시부도로의 곡선구간에서 주행차량의 횡방향 이격량을 분석하여 차량 주행에 필요한 최소 소요차로폭을 산정하였으며 본 연구결과와 선행연구에서 제시된 직선구간에서의 최소 소요차로폭을 비교 분석하였다. 이를 바탕으로 도로의 선형과 차종에 따라 곡선구간에서의 최소 소요차로폭을 제시하였다. 조사대상 곡선구간 도로의 차로폭은 2.79m~3.40m이다. 주행차량의 횡방향 이격량의 분포 및 조사대상 차량의 85%를 기준으로 누적분포를 분석하였다. 분석결과 곡선구간에서의 최소 소요차로폭이 소형차량의 경우 2.31m~2.58m, 대형차량의 경우 2.80m~3.27m로 산정되었다. 본 연구결과는 녹색교통 도입을 위한 공간, 도로공사 중, 소형차 전용도로의 건설 등에 활용될 수 있을 것이다. 또한 설계자의 목적에 따라 유연한 차로폭 설계기준의 적용에 필요한 기초적인 연구로 활용될 수 있을 것으로 기대된다.

현행 도로설계의 기준이 되는 "도로의 구조 시설 기준에 관한 규칙 해설 및 지침"에서는 설계속도에 따라 도로 선형별 최소 설계기준을 정하고 있으며, 이 기준을 만족시키면 교통안전성 이 확보되는 것으로 규정하고 있다. 이러한 설계기준에 적용되고 있는 개별 설계요소들은 원칙적으로 차량 및 운전자 특성을 감안하여 설치기준이 정립되었으나, 설계요소간의 연관성 또는 일관성에 대한 깊이 있는 연구를 통해 제반 기준이 정립된 것은 아니다. 결과적으로, 현재의 도로설계기준이 개별 설계 요소들의 조합에 의해 결정되는 도로의 안전성, 일관성 문제를 모두 고려하지는 못하였다. 따라서, 본 연구에서는 기존의 설계기준에 내재된 문제점을 인지하고 해결을 위해 우선적으로 3차원 가속도를 고려한 선형 설계방안에 대한 연구를 수행하였으며, 이를 통해 더욱 안전하고 조화로운 도로건설을 유도하고자 한다.

현행의 도로설계기준에서는 특정 설계속도에 따라 최소기준을 정하여 이를 토대로 설계된 도로가 해당 기준을 만족하면 주행상 안전성을 확보하는 것으로 간주하고, 이에 따라 도로설계 및 교통운영을 시행하고 있다. 그러나 실제 도로를 주행하는 차량의 속도를 조사해보면, 다수의 차량이 설계자의 의도와 다른 속도로 주행하는 것을 볼 수 있고, 이는 도로 이용자의 안전성 문제와 직결된다고 할 수 있다. 특히, 직선부에서 곡선부, 혹은 곡선부에서 직선부로 주행하는 곡선부 변이구간은 이러한 속도의 변동이 가장 심한 구간 중의 하나로 이에 대한 주행 안전성 검토가 절실하다. 따라서 본 연구에서는 첫째, 곡선부 도로 변이구간에서의 주행속도와 주행반경을 고려한 지점별 횡방향 가속도와 횡방향 가속도 변화율을 산정하고, 둘째, 이를 고려한 곡선부 도로 변이구간의 설계안전성을 평가하여 편경사, 곡선반경 등의 선형 설계요소를 검토하였다. 검토결과 현재 고려되어지고 있는 구심가속도는 실제 운전자가 부담해야 하는 구심가속도에 훨씬 못 미치고 있는 실정이며, 설계속도에 따라 구심가속도가 25.56~77.78% 증가되어 주행안정성에 문제가 발생함을 확인할 수 있었다. 본 연구는 직선-단곡선으로 이어지는 곡선부 변이구간을 대상으로 하였다.

According as tracks are twisted on running, wheel loads applied to outer rail are increased on curved track. Canting on tracks considering the balance cant allows to have permissible cant deficiency. The test bed area of Ho-Nam high railway is planed for 400km/h Speedup test, cant deficiency is expected to generate centrifugal load in the curve. Therefore, Korean design criteria recommend to increase maximum 20% of wheel load. This study shows that normalized wheel load variations are analyzed its stationary in inner and outer rail when centrifugal forces in outer rail of a curve are caused by curve radius, cant, velocity. Vertical wheel loads are reviewed on the behaviors of each structural element according to the increase of velocity.