• Communications for Statistical Applications and Methods
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• 제30권1호
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• pp.95-107
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• 2023

Purpose: The statistical analysis of point processes on linear networks is a recent area of research that studies processes of events happening randomly in space (or space-time) but with locations limited to reside on a linear network. For example, traffic accidents happen at random places that are limited to lying on a network of streets. This paper applies techniques developed for point processes on linear networks and the tools available in the R-package spatstat to estimate the intensity of traffic accidents in Leon County, Florida. Methods: The intensity of accidents on the linear network of streets is estimated using log-linear Poisson models which incorporate cubic basis spline (B-spline) terms which are functions of the x and y coordinates. The splines used equally-spaced knots. Ten different models are fit to the data using a variety of covariates. The models are compared with each other using an analysis of deviance for nested models. Results: We found all covariates contributed significantly to the model. AIC and BIC were used to select 9 as the number of knots. Additionally, covariates have different effects such as increasing the speed limit would decrease traffic accident intensity by 0.9794 but increasing the number of lanes would result in an increase in the intensity of traffic accidents by 1.086. Conclusion: Our analysis shows that if other conditions are held fixed, the number of accidents actually decreases on roads with higher speed limits. The software we currently use allows our models to contain only spatial covariates and does not permit the use of temporal or space-time covariates. We would like to extend our models to include such covariates which would allow us to include weather conditions or the presence of special events (football games or concerts) as covariates.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.848-853
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• 2005

The objective of this paper is to address to the providing an adequate noise and vibration solution, required for High Speed Rail while maintaining the stability criteria of the ChonAn station structure, the first constructed in Korean High Speed Railway. The significant acoustic pressure level will be induced by the high speed trains passing-by. Therefore, the high level study of this case is necessary. The acoustic pressure level of 85 dB(A) inside the ChonAn station is expected, and the spaces below concrete slab are not suitable for commercial purpose, thus installation of filtering systems (spring boxes containing viscous dampers, ballast mats and acoustic shield) are provided to reduce the effect of the noise and vibration to acceptable level of 55 dB(A). But, a major drawback of application of the previously conducted experimental results was that the actual effect of installation of filtering system was never been validated. Therefore, the acquisition of noise and vibration on the present structure were obtained and compared to the computer simulations. These predicted the behavior of the station reasonably well. Also, the installation of filtering systems gave the superior reduction on noise and vibration. This application is successfully adapted without scarifying stability criteria related to the structural stability including excessive deformations or displacements. Three traffic operation safety limits: deck vertical acceleration, deflection of the structure, and longitudinal displacement of the slab were satisfactory.

• 한국도로학회논문집
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• 제14권6호
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• pp.121-129
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• 2012

PURPOSES : Traffic accidents at intersections have been increased annually so that it is required to examine the causations to reduce the accidents. However, the current existing accident models were developed mainly with non-linear regression models such as Poisson methods. These non-linear regression methods lack to reveal complicated causations for traffic accidents, though they are right choices to study randomness and non-linearity of accidents. Therefore, to reveal the complicated causations of traffic accidents, this study used structural equation methods(SEM). METHODS : SEM used in this study is a statistical technique for estimating causal relations using a combination of statistical data and qualitative causal assumptions. SEM allow exploratory modeling, meaning they are suited to theory development. The method is tested against the obtained measurement data to determine how well the model fits the data. Among the strengths of SEM is the ability to construct latent variables: variables which are not measured directly, but are estimated in the model from several measured variables. This allows the modeler to explicitly capture the unreliability of measurement in the model, which allows the structural relations between latent variables to be accurately estimated. RESULTS : The study results showed that causal factors could be grouped into 3. Factor 1 includes traffic variables, and Factor 2 contains turning traffic variables. Factor 3 consists of other road element variables such as speed limits or signal cycles. CONCLUSIONS : Non-linear regression models can be used to develop accident predictions models. However, they lack to estimate causal factors, because they select only few significant variables to raise the accuracy of the model performance. Compared to the regressions, SEM has merits to estimate causal factors affecting accidents, because it allows the structural relations between latent variables. Therefore, this study used SEM to estimate causal factors affecting accident at urban signalized intersections.

• Wind and Structures
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• 제29권4호
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• pp.279-297
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• 2019

Strong winds threaten the safety of vehicles on long-span bridges considerably, which could force traffic authorities to reduce speed limits or even close these bridges to traffic. In order to maintain the safe and economic operation of a bridge, a reasonable evaluation of the driving safety on that bridge is needed. This paper aims at carrying outdriving safety analyses for three types of vehicles on a long-span bridge in crosswinds by considering the aerodynamic interference between the bridge and the vehicles based on the wind-vehicle-bridge coupling vibration analysis. Firstly, CFD numerical simulations along with previously obtained wind tunnel testing results were used to determine the aerodynamic force coefficients of the three types of vehicles on the bridge. Secondly, the dynamic responses of the bridge and the vehicles under crosswinds were simulated, and based on those, the driving safety analyses for the three types of vehicles on the bridge were carried out for both cases considering and not considering the aerodynamic interference between the vehicles and the bridge. Finally, the effect of the aerodynamic interference on the safety of the vehicles was investigated. The results show that the aerodynamic interference between the bridge and the vehicles not only affectsthe accident critical wind speed but also the accident type for all three types of vehicles. Such effects are also different for each of the three types of vehicles being studied.

• 대한교통학회지
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• 제23권4호
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• pp.47-55
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• 2005

최근 폭등하는 자동차의 이용과 교통사고의 증가는 물적 손실이란 측면에서 뿐만 아니라, 국민의 기본 생활권을 위협한다는 측면에서 교통사고를 줄이기 위한 많은 노력이 요구된다. 특히, 일반 도로구간에 비해 사고의 잠재성이 상대적으로 높은 교차로의 경우 이에 대한 적절한 대책이 필요하다. 이를 위해 본 연구에서는 교차로 교통사고에 있어서 사고 심각도에 영향을 미치는 요인들을 분석하고 이를 통하여 교차로 안전성 향상에 기여하고자 한다. 사고 심각도 분석에 있어서 사고 자료의 특성을 고려하여 순서형 확률모형 중 적절한 모형을 적용하였다. 데이터의 ${\epsilon}_i$(오차항)의 분포를 정규분포로 가정하여 순서형 프로빗 모형을 적용하였고 모형의 설명력과 적합성을 나타내는 $p^2$(우도비)와 $x^2$(Chi-square)의 값을 이용하여 최적의 사고 심각도 모형을 개발하였다. 개발된 심각도 모형을 분석한 결과, 교차로 교통사고 심각도에 영향을 미치는 변수는 부도로 교통량, 주도로 중차량 비율, 주도로 우회전 비율, 주도로 조명시설, 주도로 제약시설, 부도로 좌회전 유도선 등으로 분석되었다.

• 한국컴퓨터산업학회논문지
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• 제2권4호
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• pp.417-424
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• 2001

기존의 라우터들로 구성된 인터넷 망에서 트래픽 처리 효율에 한계가 있으며, 이러한 한계를 해결하기 위하여 IP 주소가 아닌 레이블을 기반으로 하는 고속 스위칭 기술인 MPLS 시스템이 구상되었다. 그러나 기존의 ATM 기반의 MPLS 시스템은 QoS (Quality of service) 지원에 어려움이 있다. 본 논문에서는 ATM 스위치 기반의 MPLS 시스템에서 QoS 보장을 위해서 제안된 CR-LDP 프로토콜과 qGSMP 프로토콜을 이용하여 서비스 보장형 네트워크를 구성하는 방법 및 LER 시스템에서 QoS Translation 및 QoS Mapping 기능을 구현하여 implicitly하게 LSP를 설정하는 방법에 대해서 제안하였다.

• 한국ITS학회 논문지
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• 제19권5호
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• pp.40-51
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• 2020

2011년에 고속도로 정체 기준 속도가 개정된 후 많은 시간이 경과함에 따라 차량의 성능 개선, 경쟁 관계에 있는 고속열차 운행 확대, 고속도로 일부 구간의 제한속도 상향 등 다양한 고속도로 주행환경 변화가 발생하였고 고속도로 이용자의 이동 신속성에 대한 기대수준 또한 증가하는 추세이다. 따라서 본 연구에서는 설문조사를 통해 고속도로 이용자의 정체에 대한 인식을 조사하고, 고속도로 교통류 분석을 통해 고속도로 정체 기준 속도의 재설정을 검토하고자 한다. 설문조사 결과, 고속도로 이용자들이 인식하는 정체 기준 속도가 다소 높아진 것을 확인하였다. K-means 알고리즘을 통해 교통량 및 속도 자료를 분석한 결과, 서행과 정체의 분류 기준은 60km/h 수준인 것으로 나타났다. 또한 정체 기준 속도를 50km/h와 60km/h로 상향하는 것을 가정하여 고속도로 정체잦은구간을 산정해본 결과, 50km/h가 고속도로 이동성 관리를 위한 정체 기준 속도로 적절한 것으로 판단된다.

• 한국도로학회논문집
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• 제14권5호
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• pp.179-188
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• 2012

PURPOSES: The aim of this study is to analyze overloading control effectiveness of enforcing overweighted vehicles using HS-WIM (High-Speed Weigh-in-Motion) at main lane of expressway. METHODS: To analyze the weight distribution statistically, HS-WIM system should has an appropriate weighing accuracy. Thus, the weighing accuracy of the two HS-WIM systems was estimated by applying European specifications and ASTM (American Standards for Testing and Materials) for WIM in this study. Based on the results of accuracy test, overweight enforcement system has been operated at main lanes of two expressway routes in order to provide weight informations of overweighted vehicle in real time for enforcement squad. To evaluate the overloading control effectiveness with enforcement, traffic volume and axle loads of trucks for two months at the right after beginning of the enforcement were compared with data set for same periods before the enforcement. RESULTS: As the results of weighing accuracy test, both WIM systems were accepted to the most precise type that can be useful to applicate not only statistical purpose but enforcing on overweight vehicles directly. After the enforcement, the rate of overweighted trucks that weighed over enforcement limits had been decreased by 27% compared with the rate before the enforcement. Especially, the rate of overweighted trucks that weighed over 48 tons had been decreased by 91%. On the other hand, in counterpoint to decrease of the overweighted vehicle, the rate of trucks that weighed under enforcement limits had been increased by 7%. CONCLUSIONS: From the results, it is quite clear that overloading has been controlled since the beginning of the enforcement.

• 전자통신동향분석
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• 제33권1호
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• pp.89-100
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• 2018

To accommodate the rapid increase in the amount of data traffic, the capacity of datacenters is expanding rapidly. Datacenter networks (DCNs) utilize electronic packet switches. However, the increases in the speed and capacity of electronic devices are slower than that of data expansion. Furthermore, electronics are too well developed to reach very near their physical limits. To achieve a breakthrough under this situation, optical switching schemes have been widely examined to replace or collaborate with incumbent electronic switches in a DCN. This report reviews the current status of such global researches on an optical DCN.

• 한국ITS학회 논문지
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• 제16권4호
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• pp.64-75
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• 2017

기존의 고정모수를 이용한 가산모형은 관측되지 않은 이질성을 고려할 수 없으며, 계수값의 표준오차가 과소추정됨에 따라 과도한 t-값이 도출되어 모형의 신뢰성이 감소하게 된다. 또한 무신호교차로의 경우 자료 수집의 어려움과 정확한 분석과정의 통계적 한계로 신호교차로에 비해 연구가 미비한 실정이다. 본 연구에서는 Random Parameter를 이용한 가산모형을 구축하여 교통사고에 영향을 미치는 요인들을 분석하고자 하였으며, 지방부 무신호교차로를 대상으로 하여 기존 연구들과의 차별성을 두고자 하였다. 분석 결과, 총 7개의 변수가 유의한 변수로 나타났고, 이 중 2개의 변수(횡단보도 유무, 제한 속도)가 확률적 변수로 나타났다.