Due to its favorable optical properties, Cu2SnS3 (CTS) is a promising material for thin film solar cells. Doping, which modifies the absorber properties, is one way to improve the conversion efficiency of CTS solar cells. In this work, CTS solar cells with selenium doping were fabricated on a flexible substrate using sputtering method and the effect of doping on the properties of CTS solar cells was investigated. In XRD analysis, a shift in the CTS peaks can be observed due to the doped selenium. XRF analysis confirmed the different ratios of Cu/Sn and (S+Se)/(Cu+Sn) depending on the amount of selenium doping. Selenium doping can help to lower the chemical potential of sulfur. This effectively reduces the point defects of CTS thin films. Overall improved electrical properties were observed in the CTS solar cell with a small amount of selenium doping, and a notable conversion efficiency of 1.02 % was achieved in the CTS solar cell doped with 1 at% of selenium.

PURPOSES: A hard shoulder lane (HSL) is a method of solving severe traffic congestion on an expressway. Recently, it has been applied to several expressways in Korea, and there have been numerous positive effects, which include increasing the road capacity and reducing traffic congestion. However, these effects have been limited due to tunnels which created a‘ bottle-neck’effect in HSL application for longer road segments. In the tunnel sections, an HSL is generally not operational owing to problems such as narrow roads and the risk of accidents. If an HSL can be extended to tunnel segments, great positive effects can be achieved. Therefore, this study was conducted to evaluate driver behavior and stability to investigate the risk of HSL in tunnels. METHODS: The Driving Simulator experiments were conducted using some scenarios for the Geumnam and Seojong tunnels on the Seoul- Chuncheon Highway. Based on data from the experiments such as running speed, lateral replacement, and steering handling, the running stabilities of participants were analyzed. In addition, traffic flow data from VDS(Vehicle Detection System) were analyzed as before-after studies. RESULTS: Although there were some differences in driving behaviors, most participants showed safe driving behavior at a speed of less than 50 km/h. CONCLUSIONS : Based on driving behaviors and traffic flow analyses, it is concluded that HSL in tunnels can be an alternative to increase efficiency based on safe driving environments for speeds of below 50 km/h.

PURPOSES : The purpose of this study is to develop a service volume for signal metering on roundabouts to increase applicability of roundabout in Korea. METHODS: To develop the service volume for signal metering on roundabouts, traffic simulation studies were conducted using VISSIM software for various scenarios based on traffic volumes as approaches and location of detectors on controlling approach lane. Typically, the Vehicle Actuated Programming module in VISSIM was applied for analyzing more realistic traffic signal control conditions. RESULTS: As the left-turning volume is increased, the delay reduction rates were increased. And the case of 40 meter distance of a detector and 20 seconds red signal phase made better results. CONCLUSIONS: The signal metering on roundabout should be applied carefully because it is possible to lose roundabout strengthen in traffic operation aspect. The service volume for signal metering on roundabouts that suggested from this study is useful to decide the application of signal metering on roundabout.

PURPOSES : This study was conducted to develop expressway safety treatments based on the analysis results of older driver behaviors through literature review, surveys, and driving simulator experiments. METHODS: In this study, three analyses were conducted: surveys of 700 older drivers to find the risk segments they recognized, driving simulator experiments with older and younger drivers to investigate driver behaviors, and expert surveys to find the priority of expressway safety treatments for older drivers. RESULTS : Through survey results it was found that merging areas and tunnels were identified as the most dangerous areas, and more dangerous older driver behaviors were observed on those expressway segments in the driving simulator experiments. In addition, the priorities of safety treatments for each segment of expressways were decided based on expert surveys. CONCLUSIONS: It was concluded that choice and concentration strategies of expressway safety treatments for older drivers should be applied as perceptions regarding dangerous spots and older driver behaviors, including geometric designs, safety facilities, regulation, and institutes to improve expressway safety.

PURPOSES : This study was conducted to analyze the effects arising from extending the duration of nighttime road construction on improving road quality and durability. METHODS : Most previous studies estimating the social cost of various construction conditions did not consider road pavement cooling time as a factor in improving road pavement quality. This study investigated the feasibility of achieving higher road quality and durability by extending the duration of nighttime road construction time extension. For this investigation, the effects of such an extension on traffic conditions were analyzed based on micro-simulation studies and scenario-based cost-benefit analyses, using factors including traffic volume, delay, construction cost, and road pavement cooling time. RESULTS : The results of the traffic simulation studies and cost-benefit analyses indicate that the current road construction method that emphasizes completing nighttime road construction by 6 a.m. reduces pavement life while causing relatively little traffic delay. If the night construction time is instead extended to 2 p.m., road pavement lifetime is increased, reducing road re-construction cost. These savings are greater than the cost of congestion arising from extending the duration of nighttime construction. CONCLUSIONS : The current nighttime construction durations need to be extended in order to efficiently manage roads and reduce road management costs.

PURPOSES :A complete signal system is not always the best solution for improving traffic operation efficiency at intersections. An alternative solution is to use a Protected Permitted Left Turn (PPLT) operation method. However, the PPLT method needs to be developed after a detailed study of driving tendencies, most notably the gap acceptance behavior, for successful implementation. In this study, the gap acceptance behavior was investigated under various variables and weather conditions, especially under rain, and the results were compared to the case of normal weather. The results of this study will be helpful in introducing the PPLT method, and are important considering the tendency of attempting unprotected left turns that is extremely common in Korean drivers.METHODS :Data was obtained by analyzing traffic footage at four intersections on a day when the precipitation was greater than 5 mm/h. The collected data was classified into seven variables for statistical analysis. Finally, we used logistic regression analysis to develop a probability distribution model.RESULTS :Gap, traffic volume, and the number of conflicting lanes were factors affecting the gap acceptance behavior of unprotected left turns under rainy conditions.CONCLUSIONS :The probability of attempting unprotected left turns is higher for larger gaps. On the other hand, the probability of attempting unprotected left turns decreases with an increase in the traffic volume. Finally, an increase in the number of conflict lanes leads to a decrease in the probability of attempting unprotected left turns.

PURPOSES : In this study, the effects of installation of diagonal crosswalks on traffic flow depending on the types of intersections are analyzed. METHODS : Scrambled crosswalks have advantages in the traffic safety. Therefore, a comparative analysis of the overall average delay before and after installation of the scrambled crosswalk was conducted using VISSIM. RESULTS: The overall average delay for the scrambled crosswalk decreased when the traffic volume ratio of the major to the minor street is 1: 6 in 2-by-1 and 3-by-1 types of intersections. The scrambled crosswalk improved efficiency of traffic operation in intersections: higher traffic volume for a major street, lower traffic volume for a minor street, and longer cross-distance for a major street. CONCLUSIONS: This study can be used to determine when a scrambled crosswalk should be installed to improve operational efficiency.

PURPOSES : Permitted left turn is a turning maneuver in which a vehicle turns left using a gap between oncoming vehicles, called gap acceptance, and it enables for more efficient traffic operation at intersections. In Korea, the permitted left turn has not been a common maneuver at signalized or un-signalized intersections. However, many experts and the Police Agency tried to apply this effective turning maneuver at intersections in Korea since 2010. Though the investigation of gap acceptance is significantly important in understanding a driver’s behavior at intersections, there have not been many studies about this topic, specifically a study to develop probability models of gap acceptance behavior. METHODS: In this study, the probability model of gap acceptance behavior for a permitted left turn was developed based on observational field studies. To develop the model, seven variables were analyzed including gap, waiting time, traffic volume, conflict-flow vehicle type, leftturning vehicle type, the number of lane, and time. RESULTS: In the final model, gap and left-turning vehicle type were found to be significant influencing factors. CONCLUSIONS: Through this model development, it was concluded that as the gap size increased, the probability of gap acceptance was higher. Moreover, when a left-turning vehicle was a passenger car, the probability of gap acceptance was higher than compared to large size buses or freight cars.

교차로 신호계획 수립은 여러 가지 중요한 요소를 포함하고 있다. 특히 부도로의 녹색시간은 주도로를 횡단하는 보행자의 녹색시간에 영향을 받는다. 주도로의 녹색시간 또한 부도로를 횡단하는 보행자의 녹색 시간에 영향을 받지만, 도로위계상 주도로는 부도로에 비해 교통량이 많고 부도로는 비교적 차로수가 적 기 때문에 부도로의 횡단시간에 영향을 크게 받지 않는다. 그러나 부도로의 좌회전 또는 직진 교통류의 녹색시간은 최소한 주도로를 횡단하는 보행녹색시간보다 커야 한다. 이로 인해 부도로에서 진출하는 교통 량이 많지 않더라도 일정시간 이상의 녹색시간을 부여하여야 하므로 신호계획에 있어서 불필요한 시간이 발생하게 된다. 따라서 주도로의 용량이 초과되어 전체 교차로 서비스수준(LOS)은 감소하게 된다. 일반적으로 대각선횡단보도는 전체 교차로의 지체를 발생시킨다. 그러나 대각선횡단보도를 설치하게 되면 보행전용현시에서 횡단보행자를 모두 소거시킬 수 있기 때문에 위와 같은 최소녹색시간의 제약을 받 지 않고 부도로의 실제 교통량에 따라 신호계획을 수립할 수 있는 장점이 있다. 따라서 본 연구에서는 VISSIM 프로그램 분석을 통해 대각선횡단보도 설치 전․후의 평균차량지체(sec/veh)를 비교분석하였다. 분석결과를 토대로 대각선횡단보도를 설치함으로써 교차로 서비스수준(LOS)을 향상시킬 수 있는 교차로 유형과 주도로 및 ․부도로 교통량 비율을 제시하는 것을 목적으로 한다. 분석결과, 편도 2*1 교차로와 편도 3*1 교차로에서 부도로와 주도로의 교통량비가 1:6 이상일 경우 대 각선횡단보도를 설치하여도 평균차량지체가 감소하게 되는 것으로 나타났다. 즉 부도로의 교통량이 많지 않고, 주도로의 교통량이 많고 부도로보다 차로폭이 클 경우 대각선횡단보도를 설치하면 차량소통측면에 서 효과를 볼 수 있다. 본 연구의 결과는 대각선 횡단보도를 설치 시 효율적인지를 결정할 수 있는 기초결 과로 제공될 것으로 기대된다.

교통사고 잦은 곳 개선사업은 2010년까지 사업대상지점만을 선정하여 개선사업을 진행하였지만, 2011 년부터 지점뿐만 아니라 구간을 선정하여 개선사업을 추진하고 있다. 그러나 현재까지 사업대상구간을 선 정하는 방법이 명확하지 않은 문제가 있어 사업대상구간 선정 시 혼란이 가중되고 있는 실정이다. 또한 지방부 도로와 같이 교차로가 많지 않은 구간의 사업대상구간 선정은 비교적 수월하지만, 도시부 도로의 교차로가 많은 구간에서는 정량적인 기준을 통해 어떤 구간을 어떻게 선정하여야 하는지 명확한 기준이 없다. 따라서 본 연구에서는 교차로가 많은 특성을 가지고 있는 도시부 도로에서의 사고 잦은 곳 사업대 상구간을 정량적으로 선정할 수 있도록 방법론을 개발하였다. 교통사고 DB는 도로교통공단 교통사고분석시스템(TAAS)을 통해 2012년 발생한 사고 DB를 수집하였 다. 대상구간은 서울시 동작구, 경기도 안양시, 전주시 완산구 13개 축을 선정하여 교통사고 건수 및 심각 도를 분석하였다. 이를 통해 교통사고 잦은 구간을 선정하는 2가지 대안을 제시하였고, 대표성, 구간 선 정 편리성, 범용성, 시스템 적용성 측면에서 대안별 장단점을 분석하여, 최적안을 도출하였다.

현재 국내 간선도로의 80% 이상이 무조명구간이고, 도로 야간시인성 증진 시설의 설치 및 운영관리 미 흡으로 야간 주행환경이 열악한 실정이다. 이에 따라 교통사고 사망자의 50% 이상이 야간에 발생하고 있 는 문제해결을 위해 야간 주행환경 개선이 매우 시급한 실정이다. 본 연구에서는 운전자 인지행태 기반으 로 모의실험을 수행함으로서 선형유도시설의 밝기 수준별 운전자 시감과의 관계를 도출하고, 야간 도로의 시인성 평가를 위한 기초 자료로 활용하고자 한다. 여러 선형유도시설 중 갈매기 표지, 시선유도표지, 델리네이터의 밝기에 대한 만족도 조사를 실시하였 다. 이를 통해 야간 도로 선형유도시설의 밝기와 운전자가 느끼는 만족도와의 시감 관계를 도출하였다. 실험 결과, 각 시설별 자체밝기와 시감과의 관계는 선형관계를 보이지만 대비값과 시감은 선형관계를 나 타나지 않는 것으로 확인하였다. 두 요인의 시감에 대한 영향도를 자세하게 추정하기 위해 통계모형을 개발하였다. 종속변수로 설정하 는 시감이 리커드 5점 척도이기 때문에 범주형 변수이며 순서를 지니고 있기 때문에 순서형 로짓 모형을 사용하였다. 독립변수로는 자체밝기와 대비값을 설정하였는데, 두 요인의 범위가 상이함에 따른 왜곡을 최소화하기 위해 독립변수의 범위를 0~1로 변환하여 모형을 개발하였다. 순서형 로짓 모형을 이용하여 시감에 대한 자체밝기와 대비값의 영향력을 분석한 결과, 모든 모형에서 자체밝기는 크게 영향을 주는 것 으로 보이며, 대비값은 차선을 제외하고는 영향정도가 상대적으로 미비한 것으로 분석된다.

PURPOSES : This study tries to develop the accident models of 4-legged signalized intersections in Busan Metropolitan city with random parameter in count model to understanding the factors mainly influencing on accident frequencies. METHODS: To develop the traffic accidents modeling, this study uses RP(random parameter) negative binomial model which enables to take account of heterogeneity in data. By using RP model, each intersection’s specific geometry characteristics were considered. RESULTS : By comparing the both FP(fixed parameter) and RP modeling, it was confirmed the RP model has a little higher explanation power than the FP model. Out of 17 statistically significant variables, 4 variables including traffic volumes on minor roads, pedestrian crossing on major roads, and distance of pedestrian crossing on major/minor roads are derived as having random parameters. In addition, the marginal effect and elasticity of variables are analyzed to understand the variables’impact on the likelihood of accident occurrences. CONCLUSIONS :This study shows that the uses of RP is better fitted to the accident data since each observations’specific characteristics could be considered. Thus, the methods which could consider the heterogeneity of data is recommended to analyze the relationship between accidents and affecting factors(for example, traffic safety facilities or geometrics in signalized 4-legged intersections).

PURPOSES: Nighttime driving is very different from daytime driving because drivers must obtain nighttime sight-distances based on road lights and headlights. Unfortunately, nighttime driving conditions in Korea are far from ideal due to poor lighting and an insufficient number of road lights and inadequate operation and maintenance of delineators. This study is conducted to develop new standards for nighttime road visibility based on experiments of driver perception for nighttime visibility conditions. METHODS : In the study, perception level and satisfaction of nighttime visibility were investigated. A total of 60 drivers participated, including 34 older drivers and 31 young drivers. To evaluate driver perceptions of nighttime road visibility, fuzzy set theory was used because the conventional analysis methods for driver perception are limited in effectiveness for considering the characteristics of perception which are subjective and vague, and are generally expressed in terms of linguistic terminologies rather than numerical parameters. RESULTS : This study found that levels of nighttime visibility, as perceived by drivers, are remarkably similar to their satisfactions in different nighttime driving conditions with a log-function relationship. Older drivers evaluated unambiguously degree of nighttime visibility but evaluations by young drivers regarding it were unclear. CONCLUSIONS : A minimum value of brightness on roads was established as YUX 30, based on final analyzed results. In other words, road lights should be installed and operated to obtain more than YUX 30 brightness for the safety and comfort of nighttime driving.

과거 짧은 시간 내에 급격한 도로 인프라의 건설로 대다수 포장도로의 노령화 정도가 유사하고, 이에 따라 대규모 도로시설물 유지보수 사업을 위한 물량이 도출될 것으로 예상한다. 이에 대한 서울시의 예산 및 시간 제한문제를 고려할 때, 최적의 포장도로 유지 ․ 보수 전략 수립이 필요하다. 또한, 서울시 도로시 설물 공사는 주로 야간에 시행되며 도로포장면의 강성확보를 위한 타설 후 포장면 온도저하를 위한 충분 한 시간부족으로 조기파손 및 영구변형량 증가의 문제를 야기하고 있어, 도로 재포장 주기의 급격한 감소 의 원인이 되고 있다. 교통량이 많은 주간에 보수공사를 시행할 경우 도로용량을 감소시켜 교통혼잡으로 인한 사회적 비용이 발생될 우려가 있다. 국외에서는 여러 공사시간대의 교통지체, 교통량, 차량통제방안, 공사비용, 운전자지체비용을 고려한 사회적비용을 공사 전에 산출하여 비용이 최소화되는 최적의 공사시간대를 도출하는 것으로 나타났다. 하 지만, 검토한 국외 방법론은 야간공사의 제한된 공사시간으로 인한 짧은 양생 시간을 간과하였다. 따라서 본 연구는 서울시의 교통혼잡 최소화 및 양생시간 확보로 공사의 품질 보장이 반영된 사회적비용을 최소 화 할 수 있는 최적의 공사시간대를 수립하는데 목적이 있다. 본 연구에서는 야간공사로 인해 늘어나는 서울시의 재공사비용을 줄이기 위한 방안으로 야간공사의 주 간시간대 확대에 따른 비용편익 비교분석을 시행하였다. 비용편익 비교분석은 야간공사와 주간공사의 비 용분석과 편익분석으로 이루어진다. 본 연구의 비용분석으로 도로공사 자체의 사업비와 함께 야간공사와 주간공사의 지체 비용을 비교분석할 것이다. 또한 편익분석으로 도로포장 갱생시간과 수명간의 관계식을 산출하여 충분한 도로포장체의 갱생시간 확보에 따른 포장체 수명연장으로 발생하는 공사비 절감편익과 사회비용 절감편익을 계산할 것이다. 잦은 재포장에 따른 교통지체에 의한 사회비용 및 사업비 등을 고려할 때, 충분한 포장면의 온도저하시 간확보를 위한 주간시간대로의 도로공사 시간 확대는 결과적으로 6배 이상의 사회비용 절감 및 서울시의 예산절감의 효과를 가능하게 할 것으로 보인다. 도로포장면의 수명을 확보하기 위해 도로포장면 다짐 후 충분한 온도저하시간동안 차량통행을 통제하여도 실제적인 지체에 의한 사회비용은 공사비에 비해 낮은 수준이다.

PURPOSES: This study dealt with traffic accidents occurring within roundabouts. The objective of this study was to analyze safety effect by introduction of roundabouts. METHODS: In pursuing the above, traffic accident data on roundabouts are collected and compared. For the analysis, collected data were separated as all intersection points, turning lane accident, approach lane accident by geometric design. RESULTS : Through the study results, it was found that the total accidents decreased by 55 accidents/2 year with safety effect of roundabouts. Also the result shows that accidents by point of two-lane roundabout at turning lane(0.26) and approach lane(0.27) is risky than total accidents by point(0.09). Moreover, accidents by point shows high value as diameter of a roundabout is bigger. CONCLUSIONS: When a roundabout is introduced at the intersections there are safety effects by reduction of traffic accidents.

PURPOSES : The purposes of this study are to compare the day and night characteristics and to develop the models of traffic accidents. in Rural Signalized Intersections METHODS : To develop day and night traffic accident models using the Negative Binomial Model, which was constructed for 156 signalized intersections of rural areas, through field investigations and casualty data from the National Police Agency. RESULTS : Among a total of 17 variances, the daytime traffic accident estimate models identified a total of 9 influence factors of traffic accidents. In the case of nighttime traffic accident models, 11 influence factors of traffic accidents were identified. CONCLUSIONS: By comparing the two models, it was determined that the number of main roads was an independent factor for daytime accidents. For nighttime accidents, several factors were independently involved, including the number of entrances to sub-roads, whether left turn lanes existed in major roads, the distances of pedestrian crossings to main roads and sub-roads, lighting facilities, and others. It was apparent that if the same situation arises, the probability of an accident occurring at night is higher than during the day because the speed of travel through intersections in rural areas is somewhat higher at night than during the day.