• 대한교통학회지
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• 제14권1호
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• pp.51-67
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• 1996

The optimal path-finding problem becomes complicated when multiple variables are simultaneously considered such as physical route length, degree of congestion, traffic capacity of intersections, number of intersections and lanes, and existence of free ways. Therefore, many researchers in various fields (management science, computer science, applied mathematics, production planning, satellite launching) attempted to solve the problem by ignoring many variables for problem simplification, by developing intelligent algorithms, or by developing high-speed hardware. In this research, an integration of expert system technique and case-based reasoning in high level with a conventional algorithms in lower level was attempted to develop an optimal path-finding system. Early application of experienced driver's knowledge and case data accumulated in case base drastically reduces number of possible combinations of optimal paths by generating promising alternatives and by eliminating non-profitable alternatives. Then, employment of a conventional optimization algorithm provides faster search mechanisms than other methods such as bidirectional algorithm and $A^*$ algorithm. The conclusion obtained from repeated laboratory experiments with real traffic data in Seoul metropolitan area shows that the integrated approach to finding optimal paths with consideration of various real world constraints provides reasonable solution in a faster way than others.

• 한국도로학회논문집
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• 제19권3호
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• pp.65-70
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• 2017

PURPOSES : Pavement Management System contains the data that describe the condition of the road. Under limited budget, the data can be utilized for efficient plans. The objective of this research is to develop a mixed integer program model that maximizes remaining durable years (or Lane-Kilometer-Years) in road maintenance planning. METHODS : An optimization model based on a mixed integer program is developed. The model selects a cluster of sectors that are adjacent to each other according to the road condition. The model also considers constraints required by the Seoul Metropolitan Facilities Management Corporation. They select two lanes at most not to block the traffic and limit the number of sectors for one-time construction to finish the work in given time. We incorporate variable cost constraints. As the model selects more sectors, the unit cost of the construction becomes smaller. The optimal choice of the number of sectors is implemented using piecewise linear constraints. RESULTS : Data (SPI) collected from Pavement Management System managed by Seoul Metropolitan City are fed into the model. Based on the data and the model, the optimal maintenance plans are established. Some of the optimal plans cannot be generated directly in existing heuristic approach or by human intuition. CONCLUSIONS:The mathematical model using actual data generates the optimal maintenance plans.

• Management Science and Financial Engineering
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• 제12권2호
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• pp.87-110
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• 2006

In a hierarchical road network, all roads can be classified according to their attributes such as speed limit, number of lanes, etc. By splitting the whole road network into the subnetworks of the highlevel and low-level roads, we can reduce the size of the network to be calculated at once, and find a path in the way that drivers usually adopt when searching out a travel route. To exploit the hierarchical property of road networks, we define a convenient path and propose an algorithm for finding convenient paths. We introduce a parameter indicating the driver's tolerance to the difference between the length of a convenient path and that of a shortest convenient path. From this parameter, we can determine how far we have to search for the entering and exiting gateway. We also propose some techniques for reducing the number of pairs of entries and exits to be searched in a road network. A result of the computational experiment on a real road network is given to show the efficiency of the proposed algorithm.

• 대한교통학회지
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• 제27권4호
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• pp.115-126
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• 2009

일반적으로 차로변경 형태는 선택적 차로변경과 강제적 차로변경 등의 두 가지 형태로 구분된다. 선택적 차로변경은 운전자가 원하는 운전상태를 유지하기 위해 선택적으로 차로를 변경하는 경우이며 강제적 차로변경은 운전자가 현재 차로에서 반드시 차로를 변경해야 하는 경우로 합류부 또는 분류부와 같은 반복정체 구간에서 발생하므로 연속류 도로의 교통상태에 매우 큰 영향을 미치게 된다. 본 연구에서는 먼저 고속도로의 대표적인 반복정체 구간인 합류부와 엇갈림 구간에서 수집한 항공사진 개별차량 자료를 사용하여 교통량, 속도, 밀도 데이터와 차로변경 데이터를 생성하였다. 개별차량 속도 변화추이를 이용하여 각 분석구간에서 안정류와 정체류를 구분하였으며 30m 간격으로 분석구간을 구분하여 교통혼잡전과 후의 차로변경 횟수와 차로변경 지점의 변화를 차로변경 분포를 통하여 비교분석 하였고 정체 교통류를 대상으로 차로 변경 분포를 이용하여 본선차로간 전이과정에 대한 분석을 수행하였다. 본 연구는 본선 차로간의 차로변경 분포와 본선과 연결로간의 차로변경 행태가 고속도로의 교통류 흐름에 따라 변화하는 영향을 분석하여 고속도로 반복정체구간의 차로변경 모형을 개발하는데 기초이론 제시를 목적으로 수행되었다.

• 전자공학회논문지
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• 제49권11호
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• pp.24-35
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• 2012

본 논문에서는 광 이더넷 시스템에 대하여 상용 광 트랜시버 모듈의 사용이 가능하면서도 에너지 절감기능을 제공할 수 있도록 트래픽 예측모듈을 사용하는 동적 레인제어방식을 제안한다. 40/100Gbps급 상용 광 트랜시버는 4개 또는 10개의 광 트랜시버를 사용하는데 이들 각각은 트래픽 부하와 상관없이 항상 켜져 있어 많은 에너지를 소모한다. 이러한 에너지 소모를 감소시키기 위하여 제안된 동적 레인제어방식은 부하에 따라 일부 레인의 트랜시버를 끄고 나머지 활성화된 레인으로만 프레임을 처리하도록 한다. 이때 레인의 갯수가 변동될 때 발생할 수 있는 바이트 전송순서 어긋남을 보완하기 위하여 새로운 전송율 제어모듈을 xGMII 인터페이스 상위에 위치한 정합부계층에 설치하는 것을 제안하였다. 이것은 비활성화된 레인상으로 가상적인 바이트열을 삽입하는 기능을 수행하는 것으로써 이 바이트열들은 비활성화된 PMD에서 무시된다. 실제 이 모듈의 구현은 PHY모듈과 별개로 동작하므로 상용 PHY모듈의 사용이 가능한 장점을 제공한다. 이러한 시스템에서 변동되는 부하에 적응하여 활성화된 레인의 갯수를 결정하는 것이 중요하므로 구현관점에서 용이한 트래픽 예측기를 제시하였다. 이것은 주기적으로 샘플링된 현재의 송신버퍼크기와 지금까지 사용되었던 버퍼크기 예측값에 서로 다른 가중치를 부여하여 변화하는 트래픽에 적응하도록 한다. 이러한 시스템에 대하여 OMNET++기반의 시뮬레이터를 구현하여 적응정도와 에너지 절감효과를 분석하였다.

• 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.

• 대한토목학회논문집
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• 제35권3호
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• pp.663-670
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• 2015

현재 수립된 대부분의 대중교통관련 계획에서는 투자우선순위를 결정함에 있어 중요도(importance) 분석 없이 시설물 조사와 설문 조사를 통해 시설물에 대한 설치율과 만족도(performance)가 낮은 항목을 우선적으로 고려하여 투자순위를 결정하고 있다. 본 연구에서는 구조방정식모형(SEM: Structural Equation Model)을 활용하여 버스 이용자의 통행시간에 대한 중요도와 만족도를 동시에 고려할 수 있는 중요도-만족도 분석(IPA: Importance-Performance Analysis) 기법을 제시하였다. 수도권과 비수도권을 대상으로 버스이용자에 대한 IPA 분석을 실시한 결과 수도권의 경우 우선적인 개선이 필요한 항목으로는 버스정차횟수, 교차로수, 배차간격, 승차대기시간 및 신호체계 순서로 분석되었고, 비수도권의 경우 수도권의 역순인 신호체계, 승차대기시간, 배차간격, 버스전용차로 및 교차로수 순서로 분석되었다.

• International Journal of Precision Engineering and Manufacturing
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• 제6권4호
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• pp.3-7
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• 2005

Recently, vehicle simulators are widely used to evaluate driver s responses and driver assistance systems. It needs much effort to construct the virtual driving environment for a vehicle simulator. In this study, it is described how to make effectively the roads and the driving environment for a vehicle simulator. GIS (Geographic Information System) is used to construct the roads and the environment effectively. Because the GIS is the integrated system of geographical data, it contains useful data to make virtual driving environment. First, boundaries and centerlines of roads are extracted from the GIS. From boundaries, the road width is calculated. Using centerlines, mesh models of roads are constructed. The final graphic model of roads is constructed by mapping road images to those mesh models considering the number of lanes and the kind of surface. Data of buildings from the GIS are extracted. Each shape and height of building is determined considering the kind of building to construct the final graphic model of buildings. Then, the graphic model of roadside trees is constructed to decide their locations. Finally, the driving environment for driving simulator is constructed by converting the three graphic models with the graphic format of Direct-X and by joining the three graphic models.

• 도시과학
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• 제10권1호
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• pp.49-60
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• 2021

The purpose of this study is to analysis the impact on the inside of the new city when an incidents occurs on the Songdo International City connecting road, which has a limited access. The analysis data used KTDB's O/D and network data of the Seoul metropolitan area. In addition, the scenario composition applied a method of reducing the number of lanes on the road according to the situation of incidents, targeting bridges advancing from Songdo International City to the outside in the morning peak hours. The analysis method analyzed the traffic volume, total travel time, total travel kilometer, and route change in the new city based on the results of the traffic allocation model. As a result of the analysis, the range of influence was shown to two types. First, of the seven bridges, Aam 3, Aam 2, and Aam 1 were analyzed to have an impact only in some areas of the northwestern part of the new city. On the other hand, the remaining bridges were analyzed to affect the new city as a whole. The analysis results of this study are expected to be used as basic data to establish the scope of internal road network management when similar cases occur in the future.

• Structural Engineering and Mechanics
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• 제34권5호
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• pp.635-662
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• 2010

In this study, the effect of superstructure-abutment continuity on the distribution of live load effects among the girders of integral abutment bridges (IABs) is investigated. For this purpose, two and three dimensional finite element models of several single-span, symmetrical integral abutment and simply supported (jointed) bridges (SSBs) are built and analyzed. In the analyses, the effect of various superstructure properties such as span length, number of design lanes, girder size and spacing as well as slab thickness are considered. The results from the analyses of two and three dimensional finite element models are then used to calculate the live load distribution factors (LLDFs) for the girders of IABs and SSBs as a function of the above mentioned parameters. LLDFs for the girders are also calculated using the AASHTO formulae developed for SSBs. Comparison of the analyses results revealed that the superstructure-abutment continuity in IABs produces a better distribution of live load effects among the girders compared to SSBs. The continuity effects become more predominant for short span IABs. Furthermore, AASHTO live load distribution formulae developed for SSBs lead to conservative estimates of live load girder moments and shears for short-span IABs.