• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.34-40
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• 2018

In this study, the optimal buffer size is calculated for seamless video playback on a mobile device. Buffer means the memory space for multimedia packet which arrives in mobile device for video play such as VOD service. If the buffer size is too large, latency time before video playback can be longer. However, if it is too short, playback service can be paused because of shortage of packets arrived. Hence, the optimal buffer size insures QoS of video playback on mobile devices. We model the process of buffering into a discret-time queueing model. Mean busy period length and mean waiting time of Geo/G/1 queue with N-policy is analyzed. After then, we uses the main performance measures to present numerical examples to decide the optimal buffer size on mobile devices. Our results enhance the user satisfaction by insuring the seamless playback and minimizing the initial delay time in VOD streaming process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.369-376
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• 2010

At present, many problems in traffic operation and safety occurs since there is no clear design criteria on designating the not-permitted entrance/exit section at curb areas within complex areas. Even, there is no specific and detailed researches on the not-permitted entrance/exit section by now. This research calculated the proper length of the entrance/exit section at curb areas by dividing the access not-permitted section into the two sections. First, the calculation of the entrance section was done by considering the location of crosswalks, stop line clearance, the queue length of vehicles approaching to second lanes, and marginal distance for safety have been considered. Second, the calculation of the exit section was done by comparing and analyzing the distance between cars of the entrance section according to the investigation point and the distance considering the location of crosswalks, the behavior of exit vehicles and the length of vehicles. In conclusion, by presenting the proper length in consideration of the traffic operation and safety on the access not-permitted section within complex areas, it can be used as a traffic safety improvement alternative and will be contributed in establishing and operating the proper installation criteria for the access not-permitted section within complex areas.

• Journal of Korean Society of Transportation
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• v.16 no.3
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• pp.113-121
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• 1998

본 연구에서는 신호제어 및 ITS 분야에 활용하기 위한 검지 시스템을 구성하기 위 한 알고리즘의 하나인 대기 행렬 계측 알고리즘을 개발하였다. 본 연구에서는 대기열의 속 성을 standing queue와 moving queue로 구분하여, 각 속성에 따라 대기열의 발생지점을 계측한다. 알고리즘의 평가는 아주대학교 앞 4지교차로의 한 접근로에서 실시되었다. 평가 항목으로는 오차율과 통계적 검정을 실시하였으며, standing queue와 moving queue에 대 하여 주·야간 각 50개씩 sample을 가지고 실시하였다. 평가 결과 standing queue는 주·야 간 모두 비교적 우수한 것으로 평가되었으나, moving queue는 미흡한 결과를 나타내어, 좀 더 보완이 필요한 것으로 나타났다. 대기열의 속성을 standing queue와 moving queue로 분리함으로써 접근로의 상황을 더욱 정확하게 판단할 수 있을 것으로 기대된다.

• Journal of Korean Society of Transportation
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• v.14 no.2
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• pp.59-88
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• 1996

This study has determined optimal type, and location of loop detector to measure accurately traffic condition influenced by traffic variation with real time. Optimal type of loop detector for through vehicle at stop bar was determined by confidences of occupancy period, and nonoccupancy period, and so appropriate detector type for application to real time traffic control system has been decided on special loop detector.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.2
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• pp.219-230
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• 2023

Cities are continued to be highly advanced and metropolitanized. Lands adjacent to road make entry/exit connection increase along with construction of facilities for various purposes. However, in the absence of specific installation standards of entry and exit connection, inappropriate access location, types of access, and operation methods are deteriorating the level of traffic services at existing roads and intersections. Therefore, in order to minimize the traffic impact from entrances connected to minor arterial roads and colletor roads, first, this study re-established the waiting length in the intersection of upstream and downstream and length required for changing lanes and between entrance/exit and connection, considering the road and traffic environment in contact with the entrance. Second, it is suggested that the operation method depending on the connection type and whether to install left turn lane and acceleration and deceleration lane can be determined quantitatively by relation with the service level of nearby intersection after calculating the threshold amount of business site through negative social cost, which is the difference between the installation cost of the left turn lane and the acceleration and deceleration lane according to the type of access to the entrance and exit.

• Journal of Korean Society of Transportation
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• v.16 no.4
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• pp.65-74
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• 1998

본 연구에서는 부산시 도심상업지역 중 특히 노상에서 하역이 빈번하게 이루어져 교통상의 문제가 되고 있는 지구를 중심으로 하여 하역의 실태와 특성을 파악하고, 하역을 적절히 처리할 수 있는 필요 하역주차공간을 산정해 그 활용방안에 대해서 고찰을 행하였다. 본 연구를 통해 얻어진 결과를 요약하면 다음과 같다. 부산시 도심상업지역의 점포에서 반.출입되는 화물의 수송형태는 공동수송보다 개별적으로 수송되는 경우가 더 많았다. 도심상업지역의 시각별 순간노상주차현황을 보면 승용차의 비율이 높으나 화물의 반.출입에는 소형트럭이 가장 많이 이용되고 있으며 목적시설과 가까운 곳에 주차하려는 경향을 보이고 있다. 하역주차공간산정을 위해 대기행력 시뮬레이션 모델을 활용한 결과, 도심상업지역에 있어서 도로길이에 따른 불법주차 발생비율과 필요한 하역주차공간과의 관계를 명확히 할 수 있었다. 하역주차공간산정을 위해 대기행렬 시뮬레이션 모델을 활용한 결과, 도심상업지역에 있어서 도로길이에 따른 불법주차 발생비율과 필요한 하역주차공간과의 관계를 명확히 할 수 있었다. 한편, 무질서한 노상하역을 배제하기 위해서는 주차공간의 적절한 배치가 무엇보다 중요하며 또한 장기적인 안목에서 노외 하역주차공간의 확보 및 화물의 공동집배송 등에 관한 여구가 지속적으로 이루어져야 할 것이다.

• Journal of Korean Society of Transportation
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• v.20 no.4
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• pp.73-82
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• 2002

The influence of bus stops near signalized intersections is one of the important factors which cannot be negligible in the analysis of the capacity of signalized intersections. Absence of consideration of bus bay can reduce capacity and increase the time that the stop of buses block other traveling vehicles. This influence is reflected by the bus blockage adjustment factor in KHCM, but the factor does not consider the course of each bus passing the intersection. Particularly, left turn buses have more influence on the capacity than the other buses and require the minimum length of the road for lane changes. All the existing criteria can apply only to arterial roads on which mostly traffic flows are continuous. And the criteria. which can determine the optimum location and the minimum distance between a signalized intersection and a bus bay, is not prepared and the related study is insufficient. Therefore, a theoretical formula is derived in this study being based on the theories which are avaliable to apply to the situation of signalized intersections.

• 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.

• The Transactions of the Korea Information Processing Society
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• v.3 no.5
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• pp.1070-1081
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• 1996

In this research, a model was developed for estimating the queue length of vehicles, based on occupancy time of each vehicle collected by loop detectors which were setup at the upstream of urban street. The estimation model suggestes a method which minimizes architectural effects of the street, such as existence of pedestrian crossing, for future applications to the field. The estimation model suggested in this research was established based on real traffic data collected at up-stream detectors in Kangnam Subway station, Seoul, and the formula of the model is based on Multi-Polynomial equations. Consequence of the experiments showed that the model can adequately and in real-time mode measure length of the queue which were constructed at the 80 to 90 meters away from the upstream detectors. The estimation accuracy of the model was verified in statistical analysis conducted by regressing analysis and test results in real traffic situation.

• Journal of Korean Society of Transportation
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• v.21 no.4
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• pp.79-90
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• 2003

Internal metering policy(IMP) is a control strategy to improve the quality of traffic flow within a network by avoiding queue spillback or intersection blockage. It is a more aggressive control strategy than the current control strategy employed in COSMOS. A preliminary study was made to incorporate the IMP logic within the COSMOS system to improve its' functionality at oversaturated conditions. From the study results, a set of guideline for real implementation was recommended : traffic conditions, detector configurations, and control procedures, etc. A simulation study was performed to evaluate the effectiveness of the proposed guidelines. It was shown that the occurrence of queue spillback was minimized. and overall network performance was also improved by applying IMP logic as compared to COSMOS control onl.