• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.57-64
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• 2020

The leading technologies of the ADAS (Advanced Driver Assist System) are ACC (Advanced Cruise Control), LKAS (Lane Keeping Assist System), and AEB (Autonomous Emergency Braking). LKAS is a system that uses cameras and infrared sensors to control steering and return to its running lane in the event of unintentional deviations. The actual test is performed for a safety evaluation and verification of the system. On the other hand, research on the system evaluation method is insufficient when an additional steering angle is applied. In this study, a model using Prescan was developed and simulated for the scenarios proposed in the preceding study. Comparative analyses of the simulation and the actual test were performed. As a result, the modeling validity was verified. A difference between the front wheels and the lane occurred due to the return velocity. The results revealed a maximum error of 0.56 m. The error occurred because the lateral velocity of the car was relatively small. On the other hand, the distance from wheels to the lanes displayed a tendency of approximately 0.5 m. This can be verified reliably.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.131-140
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• 2012

Lane markings such as edgelines, centerlines, and lines that delineate lanes generally provide drivers with the various information for safe driving. Drivers can easily recognize the lane markings through the color differences between the markings and road surfaces during the daytime. However, it is a bit difficult for drivers to perceive them during the nighttime due to the lack of artificial lights. Although the glass beads with the 1.5-refractive index have been used to improve the visibility of the lane markings during the nighttime, it is still difficult for drivers to recognize the lane markings properly, especially during the rainy nighttime, which may often lead to traffic accidents. To improve the retroreflectivity and visibility of the lane markings during the rainy nighttime, the high refractive beads with the 2.4-refractive index are essentially required, but they do not work appropriately during the dry nighttime. Thus, the mixed materials with the 1.5, 1.9, and 2.4-refractive beads should be considered for the satisfactory implementation of the lane markings. This study reveals the best mixing rates of the beads by conducting benefit-cost analysis under various weather conditions in Korea. The analysis results show that the lane markings with the 100% of the 2.4-refractive beads provide the highest visibility of lane markings regardless of the roadway conditions, but the benefit-cost (B/C) ratio of the bead mixture is merely 0.46. The best mixing rate of the beads, from the highest B/C ratio viewpoint, was identified as the mixture with a 80% of 1.5-refractive beads and a 20% of 2.4-refractive beads. Some limitations and future research agenda have also been discussed.

• Journal of Korean Society of Transportation
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• v.25 no.2 s.95
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• pp.73-81
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• 2007

The purpose of this paper is to perform a basic study on the interaction between lanes, which can be achieved through analyzing traffic breakdown at the microscopic level. Using aerial photographic data for the microscopic analysis, this study analyzed the characteristics of traffic flow at a merging area. This research produced aggregated traffic data such as flows, speeds, and densities in 30 second intervals by lane for the macroscopic analysis and individual headway data by lane for the microscopic analysis. The paper contains an analysis of lane characteristics through flows, speeds, densities, and headway variations and also investigates the influence of ramp flows on mainline flows with space-time diagrams. Firstly, the merging area in this study is divided into three sections: before-merging, during-merging, and after-merging. The transition process was analyzed at each lane. Secondly, the breakdown was observed in detail with data divided in 50-foot units. The breakdown was checked through the relationships between ramp and freeway mainline flows, various techniques were proposed to analyze the breakdown, and the formation of breakdown was introduced as three stages in this study. In the near future, the findings of this study could contribute to determining the dynamic capacity on freeways by easily understanding changeable traffic breakdown patterns over time and space.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.79-87
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• 2007

The interchanges of urban freeways have many problems with traffic operation due to high off-ramp flows and frequent congestion at adjacent intersections. The flow exiting from off-ramps is affected by the operational status and traffic volume conditions of the nearest signalized intersection. As a result, off-ramp flow cannot exit and the queue backs up the freeway mainline when queues from the signalized intersection form up to the junction of the off-ramp and street. The spacing between an off-ramp and an adjacent intersection is likely to determine the traffic conditions at the adjacent intersection. However, the current design guidelines do not consider such a factor. This study is to develop a model calculating the spacing between off-ramps and adjacent intersections considering the signal, traffic, and road conditions. The variables affecting the model in this study are effective green time (g/C), volume-capacity ratio (v/c), the number of lanes, and off-ramp volume. Various scenarios are designed to represent the effects of the variables and the road networks are constructed using VISSIM, which is a common traffic micro-simulation software package. The queue length is derived from VISSIM and this length is considered as the recommended spacing between the off-ramp and the adjacent intersection. Through the simulation analysis, regression models are developed to calculate the queue length reflecting the various conditions such as signals, traffic, and road configurations. The developed model can be used to create road design guidelines to determine the location of off-ramps in the planning stage.

• Journal of Korean Society of Transportation
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• v.35 no.1
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• pp.79-89
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• 2017

The purpose of this study is to analyze the current right-turn operation at signalized intersections and suggest appropriate right-turn operation strategy. From field investigation, right-turn signals have not only operated various type and shape, lacking of consistency, but also there was no clear regulations or standards. It could increase drivers' confusion and cause vehicle-to-pedestrian accidents. In order to improve pedestrian safety, there is urgent need to study the regulations and standards regarding to right-turn traffic control. This study suggests appropriate right-turn signal operation strategy. In case of permissive right-turn operation, it should be stated on regulations that red light means right-turn vehicles must stop temporarily at the stop line and then turn right. Necessary conditions for installing right-turn signal for protected operation are that there should have one or more exclusive right-turn lanes and right-turn signal face should contain the lenses with three-color arrow indication. In addition, we assort right-turn operation types as permissive, protected and protected/permissive right-turn and suggest specific signal operation strategy by the types.

• International Journal of Highway Engineering
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• v.4 no.3 s.13
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• pp.43-49
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• 2002

Asphalt pavements have to perform under the conditions of heavily-loaded vehicles due to the industrialization and large temperature variance between the summer and the winter. Due to these factors, a characteristics change of early permanent deformation becomes a big issue, and to remedy this problem many research to use modified asphalt are being widely conducted. However, most of the modified asphalt is being paved after milling the surface course and applying tackcoating, and it is being used mostly for the repair and maintenance purpose rather than pavement of new national road. The purpose of this investigation is to obtain some fundamental data for the evaluation of the performance and long-term performance of the construction material mixtures by the laboratory test and field experiments. For the field experiment, 200m of two-lanes national road, that is being paved for the new national road under the direction of Pusan Regional Construction Management Office, was paved with SBS PMA and PSMA asphalt mixtures, which are an modified asphalt mixtures used for the surface course, on top of the base course paved with other modified asphalt mixtures. The remaining section of the new national road was paved with dense grade mixture. The laboratory tests assessed and analyzed the mixture characteristics by Marshall's stability test, strength tests and wheel-tracking test. On the basis of the evaluation result of the temperature control and roughness of the newly constructed road at the field experiment site, it is desired to evaluate and identify the most economic modified asphalt mixtures by long-term performance evaluation and LCC(Life Cycle Cost) analysis in order to apply the test result to the design of new road construction in the future.

• Journal of Korean Society of Transportation
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• v.20 no.6
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• pp.115-128
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• 2002

Traffic engineers have developed and implemented various microscopic simulation models to verify the traffic performance and to prevent the expected problems. The existing microscopic simulation models categorize drivers into several types to reflect various drivers' driving patterns but miss the dynamics of drivers' behavior changed based upon the traffic conditions. It was found from the field data collected from two different merging sections on an urban freeway in Seoul, Korea, that the drivers' critical gap distributions are changed based on (1) the traffic density on the adjacent lane to the acceleration lane and (2) the opportunities left to merge in terms of distance to the end of acceleration lane. It was also found from the study that the drivers' critical gap distributions follow the Normal distribution. and its mean and variance change while a vehicle progresses on an acceleration lane. This paper proposes a new gap-acceptance model developed based on a set of drivers' critical gap distributions from each segment on the acceleration lanes. Through the comparison study between the field data and the results from the simulation utilizing the proposed model, it was verified that (1) the distribution of merging points on an acceleration lane to the adjacent main lane at different density levels, (2) the size of the gap accepted for merging and (3) the speed difference between the merging vehicle and the trailing vehicle at the time of merging are statistically identical to the field data at 95% confidence level.

• Journal of Korean Society of Transportation
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• v.21 no.1
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• pp.115-125
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• 2003

The concrete median barriers are the most popular safety appurtenance that can be installed on narrow medians and are effective in keeping uncontrolled vehicles from crossing into opposing lanes of traffic. It is necessary to install and maintain median barriers because it is very difficult to reserve enough room required for medians in KOREA. Also, concrete median barriers are accepted as the actual alternatives for median barriers, mostly because they require almost no maintenance even after serious collisions. Typical concrete median barriers are 810mm high and have 596mm high glare screens on top of them. However we have experienced a number of "climb" and "roll-over" accidents of heavy vehicles and most of all, there have been some serious accidents caused by the part of broken glare screens. So the improvement study of concrete median barriers started. Prior to this study, a new type of concrete median barrier was suggested which is 1,270mm high and has no glare screens on top of it. So it was required to compare the properties of various types of concrete median barriers including the new type to find the optimal type of concrete median barrier. In this study, we have evaluated the characteristics of four types of concrete median barriers (New Jersey type, F type, constant slope type, and wall type). We have performed many computer simulations for the evaluation of the crashworthiness of them, and through the simulations we have tried to find a proper type of concrete median barrier. Through the computer simulations, we evaluated the structural stability and safety of the four types of concrete median barriers. We confirmed the structural stability and safety of them But in regard to the probability of "roll-over" of heavy vehicles, the higher concrete median barriers showed better performances than the lower. As the result of this study a new type of concrete median barrier was recommended.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.23-32
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• 2007

Variable message sign (VMS), which is used for providing real-time information on traffic conditions and incidents, is one of the important components of intelligent transportation systems. VMS messages need to meet the requirements with the consideration of human factors that messages should be readable and understandable while driving. This study developed a legibility distance model for VMS messages using in-vehicle differential global positioning data (DGPS). Traffic conditions, highway geometric conditions, and VMS message characteristics were investigated for establishing the legibility model based on multiple linear regression analysis. The height of VMS characters, speed, and the number of lanes were identified as dominant factors affecting the variation of legibility distances. It is expected that the proposed model would play a significant role in designing VMS messages for providing more effective real-time traffic information.

• Journal of Korean Society of Transportation
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• v.34 no.2
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• pp.123-134
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• 2016

Traffic accident at intersections takes 44.3% of total number of accidents on entire road network of Korea in 2014. Although several studies addressed contributory factors of accidents at signalized intersection, very few is known about the factors at rural unsignalized intersections. The objective of this study is therefore to investigate specific characteristics of crashes at rural unsignalized intersection and to identify contributory factors in causing crashes by statistical approach using the Ordered Logistic Regression Model. The results show that main type of car crashes at unsignalized intersection during the daytime is T-bone crashes and the number of crashes at 4-legged intersections are 1.53 times more than that at 3-legged intersections. Most collisions are caused by negligence of drivers and violation of Right of Way. Based upon the analysis, accident severity is modeled as classified by two types such as 3-legged intersection and 4-legged intersection. It shows that contributory factors in causing crashes at rural unsignalized intersections are poor sight distance problem, average daily traffic, time of day(night, or day), angle of intersection, ratio of heavy vehicles, number of traffic violations at intersection, and number of lanes on minor street.