• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.2
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• pp.29-43
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• 2019

The calibration of microscopic traffic simulation models has received much attention in the simulation field. Although no standard has been established for it, a genetic algorithm (GA) has been widely employed in recent literature because of its high efficiency to find solutions in such optimization problems. However, the performance still falls short in simulation analyses to support fast decision making. This paper proposes a new calibration procedure using a dual GA and central composite design (CCD) in order to improve the efficiency. The calibration exercise goes through three major sequential steps: (1) experimental design using CCD for a quadratic response surface model (RSM) estimation, (2) 1st GA procedure using the RSM with CCD to find a near-optimal initial population for a next step, and (3) 2nd GA procedure to find a final solution. The proposed method was applied in calibrating the Gipps car-following model with respect to maximizing the likelihood of a spacing distribution between a lead and following vehicle. In order to evaluate the performance of the proposed method, a conventional calibration approach using a single GA was compared under both simulated and real vehicle trajectory data. It was found that the proposed approach enhances the optimization speed by starting to search from an initial population that is closer to the optimum than that of the other approach. This result implies the proposed approach has benefits for a large-scale traffic network simulation analysis. This method can be extended to other optimization tasks using GA in transportation studies.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.3
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• pp.38-50
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• 2023

Recent advances in artificial intelligence (AI) technology have enabled the integration of AI technology into image sensors, such as Closed-Circuit Television (CCTV), to detect specific traffic incidents. However, most incident detection methods have been carried out using fixed equipment. Therefore, there have been limitations to incident detection for all roadways. Nevertheless, the development of mobile image collection and analysis technology, such as image sensors and edge-computing, is spreading. The purpose of this study is to estimate the reducing effect of the incident detection time according to the introduction level of mobile image collection and analysis equipment (or connected vehicles). To carry out this purpose, we utilized data on the number of incidents collected by the Suwon branch of the Gyeongbu expressway in 2021. The analysis results showed that if the market penetration rate (MPR) of connected vehicles is 4% or higher for two-lane expressway and 3% or higher for three-lane expressways, the incident detection time was less than one minute. Furthermore, if the MPR is 0.4% or higher for two-lane expressways and 0.2% or higher for three-lane expressways, the incident detection time decreased compared to the average incident detection time announced by the Korea Expressway Corporation for both two-lane and three-lane expressways.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.815-825
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• 2000

In the present work Einstein's(l942) suspended load equation IS refined in vanous aspects. After checking the flow characteristics a new method is presented for the estimation of zero velocity point at the condition of smooth turbulent flow, and non-dimensional number of suspended load is introduced for the clear representation of suspended load equation. And a recent equation of bed load is employed in order to calculate accurately the sediment concentration at a reference point. Several approximation equations are also developed to compute directly or explicitly two integrals introduced in the equations. The refined equation has been tested against the measurement data collected by Brownlie(l981) in comparison with Einstein's original equation.uation.

• Journal of Korean Society of Transportation
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• v.32 no.2
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• pp.170-178
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• 2014

Until now, several research on the relationship of traffic crash occurrences and geometric had been conducted and revealed that projects of road alignment, geometric improvement and hazardous segment selection reduced the number of accidents and accident severities. However, such variables did not consider the non-homogeneous characteristics of roadway segments due to the difficulty of data collection, which results in under-estimation of the standard error affecting the overall modeling goodness-of-fit. This study highlights the importance of non-homogeneity by looking at the effect of the non-homogeneous geometric variables through the modeling process. The model delivers meaningful results when using some geometric variables without relevant geometrics' variables.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.167-172
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• 2000

This paper is aimed at developing an location tracking for mobile station employing currently available mobile communication network of cellular phone and PCS(Personal Communication System). When the location tracking of mobile stations is in services, the services such as Emergency-119, crime investigation, effective urban traffic management or the safety protection of Alzheimer's patients, ran be available. This paper is to track the mobile station in communication network in NLOS environment. To achieve reduction of the standard noise, Kalman filter is used. In terms of the distance, positions are located by using TOA and TDOA methods in the environment that removes NLOS bias in the measured data. And then smoothing method is used. to achieve reduction of the position error values

• Journal of Korean Society of Transportation
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• v.30 no.5
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• pp.3-10
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• 2012

This study dealt with traffic accidents occurring within roundabouts. The objective was to develop roundabout accident models for different driving types by using simultaneous equations. In pursuing the above, this study used a statistical program SPSS 17.0 to accommodate data from 148 accidents occurred within 39 roundabouts of Korea. In addition, the 2SLS(2 stage least square) estimation method was adopted to calibrate the models. The main results are as follows. First, both the number of accidents and the EPDO were evaluated to have bilateral relationships. Second, all 6 different simultaneous equation models according to driving types were found to be statistically significant. Third, the developed models were compared to each other with respect to either common or specific variables. Finally, variables such as ADT, conflicting rate, heavy vehicle ratio, circulatory roadway width, number of circulatory roadway lane, approach lane width, average approach lanes, parking places, and bus stops were selected as independent variables for the models.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2263-2268
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• 2015

This paper describes packet scheduling techniques that can be used to alleviate the impact of interference. The mechanism is consisted of interference estimation and master delay police. Proposed scheduling police is effective in reducing packet loss and delay. Another advantage worth mentioning, are the additional saving s in the transmitter power since packet are not transmitted when channel is bad. This paper gives that scheduling policy works only with data traffic since voice packets need to be sent at fixed intervals. However, if the delay variance is constant and the delay can be limited to a slot, it may be worthwhile to use DM packet for voice.

• Asian Journal of Atmospheric Environment
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• v.5 no.1
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• pp.41-46
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• 2011

The port of Busan is the fifth busiest container port in the world in terms of total mass of 20-foot equivalent units transported. Yet no attempts have been made to estimate the greenhouse gas (GHG) emissions from the port of Busan by accounting for all port-related activities of the various transportation modes. With these challenges in mind, this study estimates the first activity-based GHG emissions inventory in the port of Busan, which consists of four transportation modes: marine vessels, cargo-handling equipment, heavy-duty trucks, and railroad locomotives. The estimation results based on the most recent and complete port-related activity data are as follows. First, the average annual transportation GHG emission in the port of Busan during the analysis period from 2000 to 2007 was 802 Gg $CO_2$-eq, with a lower value of 773 Gg $CO_2$-eq and an upper value of 813 Gg $CO_2$-eq. Second, the increase in the transportation-related GHG emissions in the port of Busan during the analysis period can be systematically explained by the amount of cargo handled ($R^2$=0.98). Third, about 64% of total GHG emissions in the port of Busan were from marine vessels because more than 40% of all maritime containerized trade flows in the port were transshipment traffic. Fourth, approximately 22% of the total GHG emissions in the port of Busan were from on-road or railroad vehicles, which transport cargo to and from the port of Busan. Finally, the remaining 14% of total GHG emissions were from the cargo handling equipment, such as cranes, yard tractors, and reach stackers.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.191-199
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• 2017

PURPOSES : The objective of this study is to develop a methodology to estimate the minimum required separation distance (MRSD) between a vehicle and a bicycle when overtaking. METHODS : Three steps have been conducted to develop a methodology to estimate MSRD. First, a literature review has been conducted on the measurement of MSRD, and how it may be applied in Korea. Second, two assumptions have been made to develop a methodology to estimate the MSRD. The first assumption is that the maximum separation distance between a vehicle and a bicycle can be observed when they are at the same location longitudinally. In addition, it is assumed that the separation distance is invalid when the contra-flow exists. Finally, three cameras were installed at a height of 10 m to record the vehicle-bicycle interaction. Moreover, the vehicle trajectories as well as the separation distance were coded and analyzed. Through the hypothesis test and the interval estimation, the sample mean was tested and the confidence interval was estimated. RESULTS : 141 records of separation distance data were collected, and the hypothesis test demonstrated that the MSRD in Korea is significantly higher than other countries. In addition, the confidence interval of the population mean of MSRD is from 1.51 m to 1.65 m with 95% level of confidence. CONCLUSIONS : It is expected that the proposed methodology to estimate MSRD would be beneficial in studying road safety of vehicles and bicycles. Also, the proposed MSRD is expected to be designated in the act of road and transportation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.288-300
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• 2002

In this paper, a novel method of equalization of RF transceivers is suggested for MIMO(Multiple Input Multiple Output) antenna actively studied for high speed data transmission in the recent IMT-2000 system. The core of suggestion is in equalizing the transfer characteristics of multiple transceivers using feedback and memory during the predefined calibration time. This makes it possible to weight the signals in the intermediate frequency, which is easier in the application of recently developed DoA(Direction of Arrival) algorithms. In addition, the time varying optimum cell formation according to traffic is feasible by antenna beam-forming based on the DoA information. The suggested method of equalizing multiple transceivers are successfully verified using envelope simulation. two outputs. This paper is concerned with the diagnosis of multiple crosstalk-faults in OSM. As the network size becomes larger in these days, the convent.
nal diagnosis methods based on tests and simulation be.
me inefficient, or even more impractical. We propose a simple and easily implementable alg？ithm for detection and isolation of the multiple crosstalk-faults in OSM. Specifically, we develop an algorithm for isolation of the source fault in switc.
ng elements whenever the multiple crosstalk-faults are.
etected in OSM. The proposed algorithm is illustrated by an example of 16$\times$16 OSM.