• International Journal of Highway Engineering
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• v.10 no.4
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• pp.53-63
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• 2008

Even though accident frequencies in roadway segments have been decreasing since 2000, there has been increasing the number of vehicle crashes at intersections. Due to this increase, safety problems at intersection recently started to be regarded as significant issues. The purpose of this study is to analyze the effects of road conditions, traffic operational conditions, and other influencing condition on intersection safety. Then a traffic accident frequency prediction model to evaluate the safety at intersections was developed based on the correlations between influencing factors and vehicle crashes. In this research, critically significant factors affecting vehicle crashes at rural four-legs signalized intersections were investigated. It was found that Poisson regression was the best fit method to developing a accident frequency modeling using the collected data in this study. Through this study, it was concluded that exclusive left turn lane, crosswalk, posted speed, lighting, angle, and ADT are significant influencing factors on the intersection safety.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.169-178
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• 2008

Level of Service (LOS) is one of ways to evaluate operational conditions. It is very important factor in evaluation especially for the facility of highways. However, some studies proved that ${\upsilon}/c$ ratio and accident rate is appeared like a second function which has a U-form. It means there is a gap between LOS and safety of highway facilities. Therefore, this study presents a method for evaluation of a signalized intersection which is considered both smooth traffic operation (delay) and traffic safety (accident). Firstly, as a result of our research, accident rates and EPDO are decreased when it has a big delay. In that reason, it is necessary to make a new Level of Service included traffic safety. Secondly, this study has developed a negative binominal regression model which is based on the relation between accident patterns and stream. Thirdly, standards of LOS are presented which is originated from calculation between annual delay costs and annual accident cost at each intersection. Lastly, worksheet form is presented as an expression to an estimation step of a signalized intersection with traffic accident prediction model and new LOS.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.79-86
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• 2010

This study deals with the roundabout installed at the diamond interchange. The goal is to analyze the relative effectiveness of roundabout to signalized intersection. In pursuing the above, this study gives the particular attentions to comparing the performances using VISSIM software. The main results analyzed are as follows. First, the single and double roundabouts are analyzed to have the rapid change of delay in the case of total entering vehicles of more than 2,400pcph for directional rate 10:5:5, 2,800pcph for 10:8:2, and 4,400pcph for 10:2:8. Second, the roundabouts are evaluated to be more effective than signalized intersection in the case of total entering vehicles of less than 4,000pcph for directional rate 10:5:5, and 4,400pcph for 10:2:8. In the case of directional rate 10:8:2, double roundabout of total entering vehicles less than 5,600pcph is analyzed to be more effective than signalized intersection. Finally, the performance of double roundabout is analyzed to be very similar to that of single roundabout in the case of total entering vehicles less than 4,400pcph. However, the double roundabout is evaluated to be more effective than single in the case of total entering vehicles more than 4,400pcph.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.3
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• pp.52-63
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• 2009

Recently in Korea, in the case of metropolis, the urban signalized intersections are controlled by traffic information center or ITS center. Cheon-an City also established traffic information center through the 1st.-$\sim$3rd. ITS public construction and has managed this center that includes bus information service, traffic information collection and providing service, parking information service, and traffic responsive control system. In the Cheon-an metropolitan traffic signal operation, traffic signal controllers were grouped by the each main traffic flow axes and performed with coordinated signal timing for the signalized arterials, and also cycle and split changed by realtime traffic demands. Cheon-an urban traffic responsive control system was evaluated by intersection delay and speed, then it was verified that the delay decreased and vehicle speed improved. However, the rural signal control system to connect adjacency town was evaluated to have lower status than urban area due to the unimproved TOD (Time of day) plan. Therefore actuated signal control was examined for substitutive control system in isolated signal intersection. The aim of this article is to compare actuated signal control with TOD mode in the rural intersection of Cheon-an and to fine superiority of these two control mode, with evaluation of vehicle delay by using HCM(2000) method and by micro-simulation CORSlM. The result of field test show that actuated signal control gave better performance in delay comparison than the existing TOD signal control. And simulation outcome verified that non-optimized TOD has higher delay than optimized TOD mode, non-optimal actuated mode, and optimal actuated signal control mode. Particularly, these three modes delays had not different values according to the paired sample t-test. This is because small traffic demands were loaded in each links. This suggested actuated signal control is expected to be more effective than TOD mode in some rural isolated intersections which frequently need to survey for traffic volume.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.79-87
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• 2007

The interchanges of urban freeways have many problems with traffic operation due to high off-ramp flows and frequent congestion at adjacent intersections. The flow exiting from off-ramps is affected by the operational status and traffic volume conditions of the nearest signalized intersection. As a result, off-ramp flow cannot exit and the queue backs up the freeway mainline when queues from the signalized intersection form up to the junction of the off-ramp and street. The spacing between an off-ramp and an adjacent intersection is likely to determine the traffic conditions at the adjacent intersection. However, the current design guidelines do not consider such a factor. This study is to develop a model calculating the spacing between off-ramps and adjacent intersections considering the signal, traffic, and road conditions. The variables affecting the model in this study are effective green time (g/C), volume-capacity ratio (v/c), the number of lanes, and off-ramp volume. Various scenarios are designed to represent the effects of the variables and the road networks are constructed using VISSIM, which is a common traffic micro-simulation software package. The queue length is derived from VISSIM and this length is considered as the recommended spacing between the off-ramp and the adjacent intersection. Through the simulation analysis, regression models are developed to calculate the queue length reflecting the various conditions such as signals, traffic, and road configurations. The developed model can be used to create road design guidelines to determine the location of off-ramps in the planning stage.

• Proceedings of the KOR-KST Conference
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• 1998.10b
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• pp.149-149
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• 1998

차종구분의 필요성은 교통공학 및 계획분야에서 교통패턴을 파악할 필요가 있으며 도로의 포장설계와 같은 구조적 측면, 교통관련자료구축 등에서도 중요하다. 현재 국내에서 운영중에 있는 각종검지기 체계들은 외국에서 개발한 체계로서 여러 가지 다양한 센서를 복합구성하여 차종을 구분하는 고가의 장비들이다. 이에 대한 국내의 연구사례는 극히 드물다고 볼 수 있다. 지금까지 주를 이룬 국내 연구사례를 보면 루프검지기를 이용한 차종구분이 주를 이루고 있다. 현재 루프검지기의 대체검지기(영상검지기, 자석검지기)개발이 활발히 진행되고 있으며 본 연구에서 이용되는 검지기는 자석검지기로서 루프검지기에 비하여 설치가 간단하고 파손의 우려가 적으며 유지관리 및 보수가 손쉽고 비용면에서도 저렴하다는 것이 장점이라 하겠다. 이에 최근에 개발되어진 단일 자석검지기를 이용한 실시간 차종인식 알고리즘을 개발하고, 현장실험을 통한 현장 적용성을 검토한다. 고속도로에 설치되어 있는 자석검지기를 이용하여 자료를 수집하며 분석에 이용되는 자료는 개별차량에 대하여 자속밀도의 변화를 주파수값으로 변환한 Digital Data값이다. 그 수치를 토대로 각 차량의 점유시간을 파악하여 각 차량의 점유시간동안 파형의 특징을 추출하여 각 특징들을 기초로 하여 각 차량이 나타내는 고유의 파형을 식별하는 패턴인식 방법으로 접근한다. 본 연구에서는 검지기 매설장소의 유한성 및 연구대상 도로의 특성으로 인하여 다양한 차종의 자료수집이 용이하지 못하여 시험가능한 자료수가 많은 차종을 대상으로 분석한다. 차종인식 알고리즘상의 차종분류는 건설교통부 차종분류기준에 따라 우선 구분이 확실한 차종으로 나눈후 단계적으로 세부적 차종분류로 접근한다.의 영향들을 고려함으로써 가로망 설계 과정에서 가로망의 상반된 역할인 이동성과 접근성의 비교가 가능한 보다 현실적인 가로망 설계 모형을 구축하고자 한다. 지금까지 소개된 가로망 설계모형들은 용량변화에 대한 설계변수의 형태에 따라 이산적 가로망 설계 모형과 연속적 가로망 설계모형으로 나뉘어지게 된다. 본 논문의 경우, 계산속도의 향상 측면에서는 연속적 가로망 설계 모형을 도입할 수 있지만, 이때 요구되는 도로용량이 이산적인 변수(차선 수)로 결정되어야만 신호제어 변수를 결정할 수 있기 때문에, 이산적 가로망 설계 모형이 사용된다. 하지만, 이산적 설계모형의 경우 조합최적화 문제이므로 정확한 최적해를 구하기 위해서는 상당한 시간이 소요되며, 경우에 따라서는 국부 최적해에 빠지게 된다. 이러한 문제를 극복하기 위해, 우선 이상적 모형의 근사화, 혹은 조합최적화문제를 위해 개발된 Simulated Annealing기법의 적용, 연속적 모형의 변수를 이산화하는 방법 등 다양한 모형들을 고려해 본 뒤, 적절한 모형을 적용할 것이다. 가로망 설계 모형에서 신호제어를 고려하기 위해서는 주어진 가로망에 대한 통행 배정과정에서 고려되는 통행시간을 링크통행시간과 교차로 지체시간을 동시에 고려해야 하는데, 이러한 문제의 해결을 위해서 최근 활발히 논의되고 있는 교차로에서의 신호제어에 대응하는 통행배정 모형을 도입하여 고려하고자 한다. 이를 위해서 지금까지 연구되어온 Global Solution Approach와 Iterative Approach를 비교, 검토한 뒤 모형에 보다 알맞은 방법을 선택한다. 차량의 교차로 통행을 고려하는 performance function의 경우 비신호 교차로와 신호교차로에 대

• Journal of Korean Society of Transportation
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• v.29 no.5
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• pp.79-89
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• 2011

Though many studies regarding roundabout have been recently conducted, most of them have focused on operational aspect. Moreover, majority of the previous researches analyzes operational effects of single roundabout, but seldom investigate the effects of multi-roundabouts constructed on road networks. In this study, we seek ways to construct multiple roundabouts on road network maximizing their operational effects. The analysis investigate influence of both adjacent signalized and unsignalized intersections as well as influence of the distance from those intersections to roundabouts. The results show that the optimal distance between two adjacent intersections were calculated to be 150m, and any two intersections located within 150m apart influence each other thus imposing operational restrictions on each other. In addition, those results are confirmed using simulation analysis conducted on the real urban network in Nonheon regional area, Incheon City.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.6
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• pp.54-63
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• 2014

Traffic accident frequency and severity level in Korea are known to be very serious. Especially the number of pedestrian fatalities was much worse and 1.6 time higher than the OECD average. According to the National Police Agency, the flash signals are reported to have many safety benefits as well as travel time reduction, which is opposed to the foreign studies. With this background of expanding the flash signal, this research aims to investigate the overall impact of the flash signal operation on safety, investigating and comparing the accident occurrence on the flash signal and the full signal intersections. For doing this accident prediction models for both flash and full signal intersections were estimated using independent variables (geometric features and traffic volume) and 3-year (2011-2013) accident data collected in Seoul. Considering the rare and random nature of accident occurrence and overdispersion (variance > mean) of the data, the negative binomial regression model was applied. As a result, installing wider crosswalk and increasing the number of pedestrian push buttons seemed to increase the safety of the flash signal intersections. In addition, the result showed that the average accident occurrence at the flash signal intersections was higher than at the full signal-operated intersections, 9% higher with everything else the same.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.83-92
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• 2007

In 2004, the number of traffic crashes and deaths in Korea are 220,755 and 6,563, respectively. Korea Road Traffic Safety Authority reported that the number of traffic accidents occupies over 25% out of total accidents, and found that traffic crash probability is extremely high at intersections since intersections have various traffic conflict points. A Safety study using Traffic Conflict Technique is much more useful than a study using reported traffic accident data. Existing traffic conflict research hardly considered conflict severity occurring at intersections. So, the study developed new criteria considering conflict severity. Analytic methods precisely detecting crashing points using field surveying data, and applied an application of our new criteria. Opposing left-turn conflict criteria was devided by three groups(high severe conflict, middle severe conflict, and less severe conflict) based on conflict boundary by means of a standard vehicle length. After analyzing field surveying data(3hours), we found totally 41 opposing left-turn conflicts. 3 cases are high severe conflict, and another 10 cases are middle severe conflicts, and the other cases are less severe. Studies related in conflict severity are considerably important to evaluate intersection's detailed safety index, and existing studies(purely conflict counting does not consider severity) have a limitation to clearly determine the level of safety of intersections for an application.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.31-40
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• 2003

Unsignalized intersections are classified into two-way-stop-controlled(TWSC) and all-way-stop-controlled(AWSC) intersections for the analysis of capacity and level of service. There is no AWSC intersection in Korea, but non-controlled intersections are common. Non-controlled intersections are operated only by the driver's decision without any control. However, the study for the analysis of capacity and level of service of the non-controlled intersection has been rare. As the first stage research, this study aims to determine the measure-of-effectiveness (MOE) for the performance evaluation of non-controlled intersections. The relationships between traffic volume and the intersection passing time (delay) and number of conflicts on each intersection are analyzed. It was found that the number of conflicts were more sensitive to the traffic volume compared with the delay. It means that number of conflicts can be the MOE for the performance of non-controlled intersection. The analysis of the number of conflicts and traffic volume showed a linear relationship, so that traffic volume can also be an MOE. The level of service of non-controlled intersection can be determined with either of the MOE's. Since the performance is also influenced by the ratio of traffic volumes of crossing streets, the traffic volume should be adjusted by the ratio. The capacity of non-controlled intersection was suggested to be 2,000veh/hr referring that of AWSC intersection in the USHCM. The criteria was suggested by evenly dividing the traffic volumes based on the capacity.