• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.2
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• pp.74-84
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• 2016

After installing roundabouts, changes of travel behaviour in the vicinity of roundabouts can cause increasing traffic volumes and unbalanced flow conditions. In that cases, the efficiency of roundabouts as a whole intersections can drop due to the insufficient gap between vehicles in the circulating lanes. The purpose of this study is developing a dynamic signal metering operation method for roundabouts in which a real time Signal Metering operation algorithm is suggested and its performance is tested by using VISSIM COM Interface(Visual Basic Application). The results of the real time Signal Metering operation show that there is a substantial delay improvements when two adjoined approaches are combined together and the flows of metering approach are less than controlling approach. Especially, the total entering flow is around 1,600 vehicle/h gives the delay reduction per vehicle of 70.9~102.2(73.8~77.8%) seconds for four-lane-approach with one-lane roundabouts.

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.493-504
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• 2007

This paper proposes a stereo vision-based forward obstacle detection and distance measurement method. In general, stereo vision-based obstacle detection methods in automotive applications can be classified into two categories: IPM (Inverse Perspective Mapping)-based and disparity histogram-based. The existing disparity histogram-based method was developed for stop-and-go applications. The proposed method extends the scope of the disparity histogram-based method to highway applications by 1) replacing the fixed rectangular ROI (Region Of Interest) with the traveling lane-based ROI, and 2) replacing the peak detection with a constant threshold with peak detection using the threshold-line and peakness evaluation. In order to increase the true positive rate while decreasing the false positive rate, multiple candidate peaks were generated and then verified by the edge feature correlation method. By testing the proposed method with images captured on the highway, it was shown that the proposed method was able to overcome problems in previous implementations while being applied successfully to highway collision warning/avoidance conditions, In addition, comparisons with laser radar showed that vision sensors with a wider FOV (Field Of View) provided faster responses to cutting-in vehicles. Finally, we integrated the proposed method into a longitudinal collision avoidance system. Experimental results showed that activated braking by risk assessment using the state of the ego-vehicle and measuring the distance to upcoming obstacles could successfully prevent collisions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.65-72
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• 2011

When an expressway intersects another expressway, a unique connector needs to be designed between the two consecutive exit ramps. In such a case, it is important to design a connector such that there is enough distance for drivers to find their way safely. A current design manual in Korea prescribes the minimum length of the connector as 240 m. In this research, we have suggested a method for calculating the minimum length of a connector in order to check the feasibility of the currently prescribed length. For this purpose, we have attempted to determine the total perception-reaction time and lane-changing time required by a driver. For determining the driver's perception-reaction time, we have used the driver's decision time in addition to the conventional 2.5 s of perception-reaction time for stopping sight distances. We have considered both the design speed and the average travel speed for the calculation of the length. To evaluate the accuracy of the new method, we have chosen four sites on expressways for which relatively high accident rates were recorded. As a result, we could verify that the current limit (240 m) was sufficient for drivers to be able to change lanes in the given specific geometry. However, the prescribed limit should be revised in case the drivers' decision time is considered to be their perception-reaction time. All new approaches for calculating the ideal length of a connector have been carried out by taking into account the design speed as well as the average travel speed. Owing to the characteristics of the specific geometry for two consecutive exit ramps and the large difference between the design speed and the average travel speed in the objective areas, it is more realistic to use the proposed method by keeping the decision time equal to a driver's perception-reaction time, in order to determine the ideal distance that should be maintained between two consecutive exit ramps.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.105-114
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• 2019

Recently, the paradigm of road policy has been focused on user safety. Recently, the number of road facility improvement project has been continuously increased but the economic feasibility (B/C ratio) is insufficient. Therefore, it is necessary to select a reasonable road improvement project through accurate and objective analysis of the road safety evaluation. In this study, to develop a new road safety evaluation method, data were collected based on the current road safety evaluation method for 75 routes including national roads and provincial ones. Based on the collected data, problems were analyzed and utilized as the basic factors of the new road safety evaluation method. Therefore, in this study, traffic accidents were reflected as a general evaluation item by weighing to solve these problems, and the evaluation items were added from experiences and ideas of the local public officials. For each evaluation item, a reasonable weight was determined through AHP (Analytic Hierarchy Process) questionnaire evaluation with highway experts. In addition, the safety index was determined based on the evaluation criteria for each evaluation item. The criteria for evaluating the danger zone are determined by the overall safety index. Finally, the criteria for selection of road improvement projects based on the overall risk level were derived.

• International Journal of Highway Engineering
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• v.18 no.5
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• pp.117-125
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• 2016

PURPOSES : The density in uninterrupted traffic flow facilities plays an important role in representing the current status of traffic flow. For example, the density is used for the primary measures of effectiveness in the capacity analysis for freeway facilities. Therefore, the estimation of density has been a long and tough task for traffic engineers for a long time. This study was initiated to evaluate the performance of density values that were estimated using VDS data and two traditional methods, including a method using traffic flow theory and another method using occupancy by comparing the density values estimated using vehicular trajectory data generated from a radar detector. METHODS : In this study, a radar detector which can generate very accurate vehicular trajectory within the range of 250 m on the Joongbu expressway near to Dongseoul tollgate, where two VDS were already installed. The first task was to estimate densities using different data and methods. Thus, the density values were estimated using two traditional methods and the VDS data on the Joongbu expressway. The density values were compared with those estimated using the vehicular trajectory data in order to evaluate the quality of density estimation. Then, the relationship between the space mean speed and density were drawn using two sets of densities and speeds based on the VDS data and one set of those using the radar detector data. CONCLUSIONS : As a result, the three sets of density showed minor differences when the density values were under 20 vehicles per km per lane. However, as the density values become greater than 20 vehicles per km per lane, the three methods showed a significant difference among on another. The density using the vehicular trajectory data showed the lowest values in general. Based on the in-depth study, it was found out that the space mean speed plays a critical role in the calculation of density. The speed estimated from the VDS data was higher than that from the radar detector. In order to validate the difference in the speed data, the traffic flow models using the relationships between the space mean speed and the density were carefully examined in this study. Conclusively, the traffic flow models generated using the radar data seems to be more realistic.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.11
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• pp.610-620
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• 2003

Various shadows are one of main factors that cause errors in vision based vehicle detection. In this paper, two simple methods, land mark based method and BS & Edge method, are proposed for vehicle detection and shadow rejection. In the experiments, the accuracy of vehicle detection is higher than 96%, during which the shadows arisen from roadside buildings grew considerably. Based on these two methods, vehicle counting, tracking, classification, and speed estimation are achieved so that real-time traffic parameters concerning traffic flow can be extracted to describe the load of each lane.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.111-135
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• 2015

Bridge behavior under passing traffic loads has been studied for the past 50 years. This paper presents how to model congestion on bridges and how the maximum dynamic stress of bridges change during the passing of moving vehicles. Most current research is based on mid-span dynamic effects due to traffic load and most bridge codes define a factor called the dynamic load allowance (DLA), which is applied to the maximum static moment under static loading. This paper presents an algorithm to solve the governing equation of the bridge as well as the equations of motions of two real European trucks with different speeds, simultaneously. It will be shown, considering congestion in eight case studies, the maximum dynamic stress and how far from the mid-span it occurs during the passing of one or two trucks with different speeds. The congestion effect on the maximum dynamic stress of bridges can make a significant difference in the magnitude. By finite difference method, it will be shown that where vehicle speeds are considerably higher, for example in the case of railway bridges which have more than one railway line or in the case of multiple lane highway bridges where congestion is probable, current designing codes may predict dynamic stresses lower than actual stresses; therefore, the consequences of a full length analysis must be used to design safe bridges.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.2 no.1 s.2
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• pp.63-73
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• 2003

COSMOS(Cycle, Offset, Split Model for Seoul), a real-time traffic adaptive signal system. estimates queue lengths on each approach on the basis of arithmetic average spot speeds calculated on loop detectors installed at each of two adjacent lanes. In this paper, A new method, a traffic volume-weighted average method, was studied and compared with the existing arithmetic average method. It was found that the relationship between the ratio of volumes of two lanes and the difference of average speed of each lane has a linear form. With field data, The two methods were applied and the proposed method shows more stable and reasonable queue estimation results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1723-1726
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• 2003

Clean and well maintained roadway signs are important for preserving driver's safety. The existing signs on the roadway must be periodically re-painted in order to maintain clean state. However, current sign painting operations are manually performed now. These are very slow and workers are exposed to very dangerous and hazard working environment. In this paper, we present the method for automating this job with gantry robot and spray system. In addition, we suggest two design concepts to resolve the problem that it is impractical to make the gantry system so big as to cover whole lane width. In order to show the validity of this system, the painting operation is simulated and experimentally executed.

• Journal of Auto-vehicle Safety Association
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• v.6 no.2
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• pp.23-28
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• 2014

Commercial vehicle ESC assessment for curvature road was conducted. The previous study of ESC activation condition for losing controllability utilizing the test protocols of double lane change and sine with dwell method was conducted without considering the geometric complexity of roadway design. Since critical rollover accidents were frequently observed in the exit ramp zone, variety of curve, slope and bank have been added for analysis conditions. Detailed feature of the ramp including location, dimension and design characteristics have been analyzed from the typical trumpet type ramp design. Analyzing accident data from 2008, two specific ramps have been selected due to their complexity in design and severity in steering operation.