고속도로 소통상태지수 개발에 관한 연구

복기찬,강정규,이승환,이승준,최윤혁 대한교통학회 2009 대한교통학회지 Vol.27 No.5

Congestion on expressways is increasing in spite of continuous road construction. In enlargement of expressway capacity to lessen congestion, a long period is needed and in the case of traffic congestion, it would be impossible to avoid long periods of traffic congestion. So, it is necessary to cope with traffic congestion through continuous traffic condition monitoring, analysis of the causes of congestion and the development of alternatives before traffic conditions worsen. A congestion index that can express traffic operating conditions measurably is needed to monitor those conditions. Thus, in this research, a new congestion index, the Traffic Condition Index (TCI), is developed. TCI is able to evaluate roads that have different grades (or design speeds) and to judge traffic condition as good, fair and poor (congested). In addition, TCI has merits in that it can strengthen the function of existing Freeway Traffic Management Systems (FTMS) and can be applied to congestion management easily: TCI calculates congestion intensity and severity using data obtained from existing FTMS. In order to validate TCI, it was applied to the Kyungbu Expressway and the Seohaean Expressway. As a result, TCI shows a good performance in the aspect of applicability and ability of presentation of traffic conditions compared with travel speed and Travel Time Index (TTI). 지속적인 도로건설에도 불구하고 이용차량의 급증으로 인해 고속도로의 혼잡은 계속 커져 가고 있다. 이를 해결하기 위한 물리적 용량 확대 즉, 도로의 신설, 확장에는 막대한 비용뿐만 아니라 용지확보의 어려움 등으로 장기의 건설기간이 소요되어 혼잡 해소 시까지 상당기간 동안 혼잡의 지속이 불가피하다. 따라서 도로 관리주체는 소통상태가 악화되기 이전에 소통상태에 대한 지속적인 모니터링을 통해 혼잡원인 분석 및 해결대안을 제시하여 적극적으로 혼잡에 대처하는 것이 요구된다. 소통상태의 모니터링을 위해서는 소통상태를 계량적으로 표현할 수 있는 지표가 필요하다. 따라서 본 연구에서는 등급(또는 설계속도)이 다른 도로에 대해 동일한 척도로 평가가 가능하고 소통원활, 혼잡 등의 상태를 구분할 수 있는 혼잡지표(종합소통지수, TCI)를 개발하였다. 또한 개발된 종합소통지수(TCI)는 고속도로 교통관리시스템(FTMS)과 같이 기 설치된 시스템으로부터 획득 가능한 교통데이터를 이용하여 혼잡도를 산출할 수 있기 때문에 기존의 FTMS를 기능적으로 보완할 수 있고 도로 관리주체가 혼잡관리에 쉽게 적용할 수 있는 장점을 지닌다. 한편, TCI의 적용성을 평가하기 위해 경부 및 서해안 고속도로에 적용하여 평균통행속도, TTI 및 TCI 결과 값을 비교하였는데, 활용도, 소통상태 표현 능력 등의 측면에서 TCI의 적용성이 우수한 것으로 나타났다.

Discriminatory Congestion Pricing of Network Services: A Game Theoretic Approach Using Adverse Selection

Sangkyu Rho,Jungnam An,정송 서울대학교 경영연구소 2007 Seoul Journal of Business Vol.13 No.1

The quality of network services deteriorates as network utilization increases beyond a certain point, i.e., congestion externalities. Many researchers have proposed congestion pricing models which internalize congestion externalities. However, most studies are based on a unit pricing which cannot reflect users different congestion sensitivities. The purpose of this paper is to propose a discriminatory congestion pricing model using adverse selection. Our pricing mechanism provides a congestion-sensitive user with a high quality service for a higher price and a congestion-tolerant user with a low quality service for a lower price. Our model allows service providers to better control congestions while maximizing their profits. The quality of network services deteriorates as network utilization increases beyond a certain point, i.e., congestion externalities. Many researchers have proposed congestion pricing models which internalize congestion externalities. However, most studies are based on a unit pricing which cannot reflect users different congestion sensitivities. The purpose of this paper is to propose a discriminatory congestion pricing model using adverse selection. Our pricing mechanism provides a congestion-sensitive user with a high quality service for a higher price and a congestion-tolerant user with a low quality service for a lower price. Our model allows service providers to better control congestions while maximizing their profits.

개별 차량 속도 데이터 기반 교통혼잡비용 추정방법 개선 연구

김성민,천승훈 한국교통연구원 2019 交通硏究 Vol.26 No.3

Traffic congestion costs refer to the costs of various types of losses resulting from traffic congestion. The traffic congestion cost is estimated by adding the vehicle operation cost and the time value cost, of which the time value cost accounted for about 80%. There have been various studies at home and abroad regarding traffic congestion cost estimation, but the traffic congestion cost based on average speed is commonly estimated. However, the following limitations arise when estimating the traffic congestion cost using the average speed. First, when using average speed, errors in congestion judgment may occur. In the case where the actual congestion traffic and the normal traffic flow are mixed, the average speed may be increased by the normal traffic, and thus the traffic may be determined as a non-congestion section even though the actual congestion occurs. Secondly, if congestion is determined according to the average speed, a dichotomous error is determined that all vehicles have experienced congestion or have not experienced congestion. Third, the error of underestimation occurs when using average speed. Since the average speed is the average value of the normal speed and the congestion speed, the congestion that is generated is offset by the normal speed and the traffic congestion cost must be underestimated. In order to improve the limitations of the average speed-based traffic congestion cost estimation method, this study proposes a traffic congestion cost estimation method based on individual vehicle speed data to estimate traffic congestion more accurately. 교통혼잡비용이란 교통혼잡으로 발생하는 다양한 형태의 손실을 화폐가치로 환산한 비용을 의미한다. 교통혼잡비용은 차량운행비용과 시간가치비용을 합산하여 추정하고 있으며, 그중 시간가치비용이 약 80%로 높은 비중을 차지하고 있다. 그동안 교통혼잡비용 추정과 관련한 국내·외 다양한 연구가 있었으나, 공통적으로 평균속도에 기반한 교통혼잡비용을 추정하고 있다. 하지만 평균속도를 활용하여 교통혼잡비용을 추정하게 될 시 다음과 같은 한계가 발생한다. 첫째, 평균속도를 사용할 시 혼잡판정에 오류가 발생할 수 있다. 실제 혼잡교통류와 정상교통류가 혼재되어 있는 경우 정상교통류에 의해 평균속도가 높아져 실제 혼잡이 발생하였음에도 비혼잡 구간으로 판정될 수 있다. 둘째, 평균속도에 따라 혼잡 여부가 결정되면 모든 차량이 혼잡을 경험했거나 혼잡을 경험하지 않았다고 판정되는 이분법적 오류가 발생한다. 셋째, 평균속도를 사용할 시 과소 추정의 오류가 발생한다. 평균속도는 정상속도와 혼잡속도의 값이 평균된 값이기 때문에 발생한 혼잡이 정상속도에 의해 상쇄되어 교통혼잡비용이 과소 추정될 수밖에 없다. 본 연구는 평균속도 기반의 교통혼잡비용 추정방법론의 한계를 개선하기 위해 교통혼잡을 보다 정확히 추정해 낼 수 있는 개별 차량 속도 데이터 기반 교통혼잡비용 추정 방법론을 제안하였다.

우리나라 대학의 투입물 혼잡도 측정

현정원 ( Jeong Won Hyun ) 한국생산성학회 2015 生産性論集 Vol.29 No.1

Input congestion is present when reducing some inputs causes some outputs. Such phenomenon is likely to be present in Korean universities. But previous studies measuring the efficiencies for Korean universities did not take the input congestion into account. Hence, this study revisited the efficiency of Korean universities with consideration of input congestion by employing T-S model(SBM DEA). T-S model divided the input congestion into strong congestion and weak congestion. This study measures the weak congestion because the definition of strong congestion is too restrictive. Strong congestion implies weak congestion, but weak congestion does not imply strong congestion. Number of full time teaching staffs, number of non-teaching staffs, and number of students are used as outputs and employment rate, domestic publication index, and international publication index as outputs. Inputs congestions are estimated for 39 research-oriented universities in 2012. 20 universities have been diagnosed with input congestion and an excessive number of students is the main sources of input congestion, Based on this study, the congested inputs are required to be removed from the inputs. The outputs augmentation such as employment rate, domestic publication index, and international publication index could have been achieved by the reduction in number of full time teaching staffs, number of non-teaching staffs, and number of students. In addition, the above unexpected input congestion from full time teaching staffs might be indicative of institutional inefficiency. Further research is necessary to examine the institutional inefficiency.

Recurrent Congestion Impact Based on Spatiotemporally Historic Congested Information -Case study: Separating Collision-Induced Congestion-

송태진 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.11

Transportation jurisdictions should monitor mobility and reliability of roadway systems in order to adequately invest capacity expansion and deployment of ITS technologies to alleviate congestion effectively and efficiently. In recent years, several link-based bottleneck identification schemes have estimated bottleneck impact factors on freeways based on the characteristics of congestion. However, those have used congestion data with no attention to distinguishing recurrent level of at the same “bottleneck” location. Most existing studies that distinguish between recurrent and non-recurrent congestion have focused on separating non-recurrent congestion from recurrent congestion only for intensity of congestion using parameters for the speed distribution in a time of day in a segment or point. As such, this study introduced a data-driven procedure for quantifying spatiotemporal “recurrent” congestion impact. In addition, this study used spatiotemporally historic congestion information and generated stochastic spatiotemporal congestion distributions in terms of congestion types. Using the relationship between the distributions of recurrent and non-recurrent congestion occurring at bottlenecks, the bottleneck impacts were estimated by capturing spatial and temporal impact of recurrent bottleneck from that of non-recurrent congestion occurring at recurrent bottleneck. The proposed approach represents a significant improvement in the understanding and monitoring of mobility on freeways. This can be directly applied to evaluate and rank bottlenecks.

소통관리 지표 개발을 위한 기존 혼잡지표의 국내 적용성평가 연구

이승준,김태영,고한검,복기찬 한국도로학회 2008 한국도로학회논문집 Vol.10 No.3

On the many highways, severe traffic congestions happen chronically and make traffic problems like reduction of mobility because of rapid increase of vehicles though road construction has been last. In order to solve these traffic problems, it is needed to find the trend and the symptom of traffic congestion and to analyze the cause of congestion and the (spatial) range affected by congestion. To develop the traffic condition monitoring index prior to doing all those things is most important. With this reason, many countries including U.S. had been developed the congestion criteria and indices. In this paper, applicability and characteristics of existing traffic congestion indices were considered and the direction for development of a new traffic condition index was suggested to achieve an effective traffic management. On the many highways, severe traffic congestions happen chronically and make traffic problems like reduction of mobility because of rapid increase of vehicles though road construction has been last. In order to solve these traffic problems, it is needed to find the trend and the symptom of traffic congestion and to analyze the cause of congestion and the (spatial) range affected by congestion. To develop the traffic condition monitoring index prior to doing all those things is most important. With this reason, many countries including U.S. had been developed the congestion criteria and indices. In this paper, applicability and characteristics of existing traffic congestion indices were considered and the direction for development of a new traffic condition index was suggested to achieve an effective traffic management.

교통혼잡비용 추정방법의 개선방안 연구

조진환,황기연 대한교통학회 2010 대한교통학회지 Vol.28 No.1

Recently, there has been increasing demand from academic society in Korea for the improvement of current traffic congestion cost estimation methods. The purpose of this study is to suggest a better way to estimate congestion cost followed by in-depth review regarding traffic congestion. The key improvements proposed in this study include: 1) adding social externality to congestion cost, 2) integrating the green house and environmental pollution impacts with congestion costs, 3) taking non-recurrent traffic congestion costs into account for the assessment, 4) revising the criteria to determining the level of traffic congestion speed, and 5) deciding how to limit congestion measurement period. It is found meaningful that the improvements, notwithstanding difficulties in their real case application, provide invaluable insights in our efforts to change the meaning of congestion cost in an era of sustainable growth. 최근 들어 학계와 연구원 등에서 기존의 교통혼잡비용 산정 방식과 내용에 대한 수정 요구가 증대하고 있다. 이에 본 연구에서는 교통혼잡비용에 대해 살펴보고, 교통혼잡비용의 개선방안을 도출하였다. 개선방안으로 교통혼잡비용에 사회적 외부비용을 추정에 포함하는 방안, 온실효과비용, 환경오염 비용 등을 교통혼잡비용의 추정에 합산하는 방안, 교통혼잡비용의 산정방법에 비 반복정체의 문제, 혼잡판단 기준속도의 문제, 혼잡시간대의 추정 문제, 통행속도 문제 등에 대한 대안을 도출하였다. 본 연구에서 제시한 교통혼잡비용 추정 개선 방안이 여러 가지 현실적용에 있어서의 어려움이 있는 한계를 가지고 있지만 지속가능한 발전이라는 시대의 흐름에 맞는 교통혼잡비용의 변화의 기초 자료로 제공하였다는 사실에 의의가 있다.

멀티미디어 서비스를 위한 DiffServ 망에서의 빠른 혼잡 제어 알고리즘

박종훈,유명식,Park Jonghun,Yoo Myungsik 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.1B

인터넷에서 멀티미디어 데이터가 트래픽의 상당 부분을 차지하면서 네트워크 혼잡 상황을 효과적으로 제어하는 방법이 필요하게 되었다. 또한 현재의 Best-effort 망을 통한 멀티미디어 데이터의 전송은 한정된 네트워크 자원과 다양한 환경 등으로 인해 QoS 보장이 어려워, 안정된 QoS를 제공하기 위한 IntServ, DiffServ 등의 새로운 QoS 망이 대두되었다. 하지만, RAP와 같은 송신측 기반 혼잡 제어 알고리즘은 흔잡 상황 제어에 ACK 응답에 따른 RTT 값의 변화를 이용하기 때문에, RTT 값이 큰 플로우는 상대적으로 RTT 값이 작은 플로우에 비해 ACK 응답이 늦어져 흔잡 상황에 대한 대처 시간이 늦어진다. 또한 DiffServ와 같은 QoS 망에는 호스트 단의 혼잡 제어알고리즘과는 별도의 혼잡 제어 알고리즘이 존재하여 호스트 단의 알고리즘에 악영향을 줄 수 있다. 본 논문에서는 네트워크 중심부의 흔잡 상황에 대하여 End-to-end ACK 응답에 의한 반응 이전에 네트워크의 혼잡 정보를 유기적으로 이용하여 혼잡 상황에 빨리 대처하는 기법을 제안한다. 제안된 기법을 통해 기존의 RTT기반의 혼잡 제어 기법의 문제점을 해결하고 그 성능을 향상 시켰다. As the multimedia application traffic takes more portion in the internet traffic, it is necessary to control the network congestion through the congestion control protocol. In addition, the QoS-enabled networks such as DiffServ become an indispensable technology when running the multimedia applications. However, the previously proposed end-to-end congestion control algorithms take the round trip time to react the network congestion. Thus, as the RTT becomes larger, the reaction against the congestion gets delayed further, while the network congestion gets worse. In addition the performance of end-to-end congestion control algorithm is degraded if the QoS-enabled network runs the congestion control mechanism in the network level without any coordination between them. In this paper, we propose the early rate adaptation protocol for the DiffServ network which effectively linke the congestion control algorithm at the host and the congestion mechanism in the network together. By taking advantage of early congestion notification from the network it is possible to react the network congestion more quickly and effectively.

고속도로상의 독립적인 반복 및 비반복정체의 영향비교

강경표,장명순 대한교통학회 2007 대한교통학회지 Vol.25 No.6

지금까지 고속도로 상에서 반복 및 비반복정체에 대한 연구가 많이 진행되어 왔지만 이들이 독립적으로 발생했을 때 교통정체의 영향에 대한 연구는 활발히 진행되지 못하고 있는 실정이다. 가장 큰 이유는 반복 및 비반복정체시 교통상황에 자료수집이 부족했으며, 뿐만 아니라 이들의 영향을 독립적/정량적으로 추정할 수 있는 분석도구의 효과적인 사용이 미비했기 때문이다. 본 연구에서는 미국 고속도로 구간의 교통정체시 수집한 교통자료를 바탕으로 시뮬레이션을 이용한 반복 및 비반복정체의 독립적인 영향을 분석하는 방법을 제시하였다. 분석결과로서 대상구간에 따라 비반복정체가 반복정체보다 고속도로기능을 크게 악화시키는 것으로 나타났다. 더불어 교통정체시 실시간 교통정보제공을 위한 기존 ITS기술들의 현장평가결과로서 안정적인 교통정체에서는 정보의 정확성은 높으나, 정체가 시작되거나 해소되는 시간대 또는 비반복정체시 제공되는 교통정보의 정확성은 낮은 것으로 나타났다. 결론적으로 본 연구에서는 비반복정체의 중요성과 더불어 제시하고 있는 반복 및 비반복정체의 영향분석 방법론은 향후 대상 고속도로의 정체해소를 위한 개선사업의 투자우선순위를 판단할 수 있는 기초연구로서 사용될 수 있을 것으로 기대된다. There have been few studies on the impacts of independent recurrent and non-recurrent congestion on freeway networks. The main reason is due partly to the lack of traffic data collected during those periods of recurrent and non-recurrent congestion and partly to the difficulty of using the simulation tools effectively. This study has suggested a methodology to analyze the independent impacts of the recurrent and non-recurrent congestion on target freeway segments. The proposed methodology is based on an elaborately calibrated simulation analysis, using real traffic data obtained during the recurrent and non-recurrent congestion periods. This paper has also summarized the evaluation results from the field tests of two ITS technologies, which were developed to provide drivers with real-time traffic information under traffic congestion. As a result, their accuracy may not be guaranteed during the transition periods such as the non-recurrent congestion. In summary, this study has been focused on the importance of non-recurrent congestion compared to recurrent congestion, and the proposed methodology is expected to provide a basic foundation for prioritizing limited government investments for improving freeway network performance degraded by recurrent or non-recurrent congestion.

이중 큐 CHOKe 방식을 사용한 혼잡제어

최기현,신호진,신동렬 한국통신학회 2003 韓國通信學會論文誌 Vol.28 No.11A

기존의 단대단 혼잡제어는 단순히 중복된 ACK 신호를 이용하여 혼잡을 처리하며 일반적으로 혼잡을 제어하는데 시간이 많이 소요된다. 이러한 메커니즘은 혼잡발생시에 TCP의 혼잡 윈도의의 크기가 동기화 되는 현상을 피할 수 없으며, 더욱이 RTT가 증가될 경우 중복된 ACK 패킷을 받기 전에 혼잡이 사라지거나 받기 전까지 전송되는 패킷으로 인해서 정확한 혼잡제어를 할 수 없다. 최근에 이러한 단대단 혼잡제어의 문제점을 개선하는 다양한 AQM(Active Queue Management)를 소개되고 있으며, 기본적으로 RED의 혼잡 제어 메커니즘을 사용한다. 본 논문에서는 우선 다양한 전송률과 혼잡에 반응하는 흐름(TCP)과 반응하지 않는 흐름(UDP)을 갖는 트래픽 상에서 RED, CHOKe, FRED 그리고 SRED등과 같은 AQM의 효과를 평가한다. 특히, CHOKe 메커니즘의 경우 혼잡에 반응하지 않는 흐름이 증가 할 경우 공평성이 떨어지는 단점을 갖는다. 따라서, 본 논문에서는 UDP 트래픽으로 부터 TCP 트래픽을 보호하기 위해 UPD 트래픽과 TCP 트래픽을 두개의 독립된 논리적인 큐에서 서로 다른 CHOKe 메커니즘으로 처리하는 이중 큐 CHOKe 메커니즘을 제안한다. 각 흐름의 정보를 유지하기 위해 LRURED에서 제안한 부분상태 정보(Partial state information)를 이용하여 트래픽 유형별로 구별하고 격리하여 보다 효율적인 혼잡제어를 제시한다. Current end-to-end congestion control depends only on the information of end points (using three duplicate ACK packets) and generally responds slowly to the network congestion. This mechanism can't avoid TCP global synchronization in which TCP congestion window size is fluctuated during congestion period. Furthermore, if RTT(Round Trip Time) is increased, three duplicate ACK packets are not correct congestion signals because congestion might already disappear and the host may send more packets until it receives three duplicate ACK packets. Recently there are increasing interests in solving end-to-end congestion control using AQM(Active Queue Management) to improve the performance of TCP protocols. AQM is a variation of RED-based congestion control. In this paper, we first evaluate the effectiveness of the current AQM schemes such as RED, CHOKe, ARED, FRED and SRED, over traffic with different rates and over traffic with mixed responsive and non-responsive flows, respectively. In particular, CHOKe mechanism shows greater unfairness, especially when more unresponsive flows exist in a shared link. We then propose a new AQM scheme using CHOKe mechanism, called DQC(Double Queue CHOKe), which uses two FIFO queues before applying CHOKe mechanism to adaptive congestion control. Simulation shows that it works well in protecting congestion-sensitive flows from congestion-causing flows and exhibits better performances than other AQM schemes. Also we use partial state information, proposed in LRURED, to improve our mechanism.